BIBLIOGRAPHY SUMALAG, DAVID I. APRIL ...
BIBLIOGRAPHY
SUMALAG, DAVID I. APRIL 2013. Tuber production of Potato Applied with
Different Volumes of Water in La Trinidad, Benguet. Benguet State University, La
Trinidad Benguet.
Adviser: Janet P. Pablo, Msc.
ABSTRACT
The study was conducted to determine the growth and yield of potato applied with
different volumes of water;determine the best volume of water for potato production; and
to determine the amount of water required at various growth stages of potato.
The different volumes of water applied on the different growth stages significantly
affected the plant height, root length, plant vigor at 75DAE, weight of non-marketable
tubers and percent survival of the potato plants.
Potato plants applied with 400ml of water during early vegetative stage, 800ml at
tuberization to bulking stage and 400ml during the maturity stage per plant produced high
percentage of survival, more vigorous plants, high yield, lesser non-marketable tubers,
longer roots and lesser malformed tubers as compared to the farmer’s practice of800ml of
water during early vegetative stage, 800ml at tuberization to bulking stage and 400ml
during the maturity stage.
. Tuber production of Potato Applied with Different Volumes of Water in La Trinidad,
Benguet | SUMALAG, DAVID I. APRIL 2013
INTRODUCTION
Potato has a great role in the agriculture economy aside from being nutritious.
Higher income and production is attained in potato production in a shorter period of time
compared to rice production. Also price and demand for potato are more stable as compared
to other cash crop vegetables where price fluctuation is very high (NPRCRTC, 1999).
According to Pereira et al. (2006) using optimal irrigation strategies with potato
can mean a healthy crop with high marketable yield potential. Growers are encouraged to
properly manage irrigation by regularly monitoring soil water to ensure that the availability
of water does not become a limiting factor in producing a high-yielding potato crop. Also,
ensure that the potato crop is well-fertilized and well-protected from pests.
In the Philippines, Benguet and Mountain Province are the major producers of
potato (Kalaw, 1987) and irrigation is one of the problems meet because production time
is within the dry months wherein availability of water is limited.
At present, excessive and deficit application of water in irrigation is one factor
which limits the production of potato in Benguet and other production areas.
As stated by the Department of Primary Industries in Victoria, Australia (2010)
potatoes are very sensitive to irrigation. Correct irrigation gives yield responses of around
0.2 tonnes/ha/mm water, which make it highly profitable. Irrigation can also be managed
to minimize or prevent some diseases and to produce tubers of the desired quality and size
required for specific use. In this case, there is a need to determine the best water
requirements of potato at various growth stages which will be useful for successful potato
production which this study aims.
. Tuber production of Potato Applied with Different Volumes of Water in La Trinidad,
Benguet | SUMALAG, DAVID I. APRIL 2013
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In addition, with the climatic change, erratic frequencies of drought and flooding is
experienced globally, thus, water management is important to study in irrigation sensitive
crops such as potato.
This study was conducted to:
1. determine the growth and yield of potato applied with different volumes of water;
2. determine the best volume of water for potato production; and,
3. determine the amount of water required at various growth stages of potato.
The study was conducted at Benguet State University Experimental Station, Balili
La Trinidad, Benguet from November 2012 to February 2013.
. Tuber production of Potato Applied with Different Volumes of Water in La Trinidad,
Benguet | SUMALAG, DAVID I. APRIL 2013
REVIEW OF LITERATURE
Effect of Water Stress on Plant
Kramer (1993) stated that water stress affects the aspects of plant growth pertaining
to the anatomy, morphology, physiology and biochemistry. So changes in the amount
required by the plant may interrupt the normal processes for plant growth such as; keeping
cells turgid making stems upright and leaves expanded to receive sunlight for
manufacturing and translocation of carbohydrates and nutrients for growth (Tisdale and
Nelson,1975); water stress reduces the capacity of protoplasm to carry on photosynthesis,
and reduce growth and photosynthesis are both affected by water stress (Ajambar, 1989);
Mumns and Pearson (1995) stated that water deficit causes low leaf water potentials
leading to decrease in translocation of carbon which is proportional to the decline in
photosynthesis and Gabutan (1989) stated that drought affects the total physiological
activity through reduction of the net assimilates, also causes early senescence in potato
through shortening the bulking period and subsequently lowering the yield.
In addition, water stress may lead to decrease in stomatal opening and lose of
turgidity in the guard cells. Eventually, the rate of photosynthesis and consequently growth
and yield also decrease where the plant may wilt or die in extreme condition. Moreover,
under excess water condition, plant growth is being toxified, and finally retards growth of
the plant. It is also said that crops in the early vegetative stage may not develop a deep root
system if light watering is done regularly. Also, excessive water affects crop growth as it
causes damages to shoots, high incidence of pests and diseases, physical destruction of
flowers and less activity of pollinators (AVRDC, 1990).
. Tuber production of Potato Applied with Different Volumes of Water in La Trinidad,
Benguet | SUMALAG, DAVID I. APRIL 2013
Irrigation in Potato Production
Irrigation in the era of “best management practices” requires the simultaneous
achievement of effective water use for profitable production and environmental protection.
Irrigation in excess of crop use should be minimized due to the risk of leaching of nitrate
and pesticide residues towards groundwater and the risk of runoff losses of sediment and
nutrients to surface water. Excessive irrigation promotes potato diseases. Yet potato is a
shallow rooted, water stress sensitive crop. Water deficits reduce tuber yields and quality.
Tuber quality parameters that are influenced by water stress include tuber grade, specific
gravity, heat necrosis, susceptibility to bruise, hollow heart, translucent-end, jelly end rot,
and the dark colour of fried strips and chips. Tuber grade, as determined by shape,
smoothness, and freedom from visible defects such as growth cracks, dumbbells, and
knobs, is highly sensitive to irrigation management deficiencies. Together these tuber
responses to deficit irrigation make potato a challenging crop to irrigate (Pereira and Shock,
2006).
Under irrigation leads to losses in tuber quality, market grade, total yield, and
contract price. However, over irrigation leads to erosion, disease susceptibility, water loss,
extra energy costs for pumping, nitrogen leaching, and increased in crop nitrogen needs.
Excessively wet soil is conducive to many tuber rotting pathogens, encouraging the
incidence of blights, rots, and wilts that can limit yield, tuber quality, tuber size, tuber dry
matter content, and crop marketability at harvest or from storage. Dense canopy growth,
long periods of leaf wetness, and high relative humidity creates microenvironments that
favour infection. Improperly managed irrigation often keeps the vines wet for long periods
of time, exacerbating the risk of infection (Eldredgeet al., 2006).
. Tuber production of Potato Applied with Different Volumes of Water in La Trinidad,
Benguet | SUMALAG, DAVID I. APRIL 2013
Irrigation management affects disease severity and management. The increased
humidity from irrigation will have greater effects where the macroclimate is humid or sub-
humid and be of less importance where it is drier. For potato grown in hot areas, sprinkler
irrigation can cool the environment, with possible reductions in physiological defects.
However, different irrigation methods can contribute to the occurrence of diseases and
pests on the crop depending on site-specific weather pattern. Wet soil is conducive to most
tuber-rotting pathogens. Excessive soil moisture following planting can promote seed piece
decay and an erratic emergence. Excessive irrigation can also erode hills, thus exposing
shallow-set tubers to greening or sunscald and infection by early and late blight pathogens
(Rowe and Secor, 1993).
Potato needs to have adequate and consistent soil water during most of its growth
stages: sprouting, vegetative, tuber initiation (tuber set), tuber bulking, and maturation
growth stages. However, excessively wet soil is conducive to many tuber-rotting
pathogens, and excessive moisture on the crop canopy encourages the incidence of foliar
blights and wilts that can limit potato performance. Also yield reductions due to over
irrigation can be attributed to poor soil aeration, increase susceptibility to rots and diseases,
and leaching of nitrogen from the shallow root zone (Eldredgeet al., 2006).
Irrigation Requirement in Potato Growth Stages
From emergence to tuber initiation, roots are in the second half of their growth.
During this period, the vine grows very rapidly, as much as doubling the canopy every
week. With rapidly increasing foliage every week, irrigation starts low, 0.5 inches of
irrigation is applied. At tuber initiation, about three weeks after emergence depending on
variety, seed health, weather, soil, and cultural practices used, about 1.5 inches of irrigation
. Tuber production of Potato Applied with Different Volumes of Water in La Trinidad,
Benguet | SUMALAG, DAVID I. APRIL 2013
is applied. A soil moisture of 70 to 80% is preferred, less than 65% field capacity would
be considered a deficit. Water deficiency at this point would inhibit canopy and root
growth, and indirectly weed control by less ground cover. An excess would retard root
branching (development) by water-logging root hairs and promote nitrogen leaching. In
short, with an increase in foliage and thereby transpiration, irrigation should begin
gradually increase as the canopy grows (University of Nebraska-Lincoln 2012). Also,
Water use rates for potato begin at about 0.4 mm per day when the crop sprouts (emerges)
and increase to as high as 7 mm per day when the potato canopy completely shades the
ground and tubers are bulking. Potato water demand decreases as the crop achieves full
tuber bulking and maturation (Efetha, 2011).
According to the University of Nebraska-Lincoln (2012) during tuberization, the
first set of tubers is being initiated and these are in slow growth, development stage, the
lag phase of tuber growth. Irrigation becomes increasingly important and water stress
becomes less tolerable. Transpiration reaches its highest rate. Optimal soil moisture is 80
to 90% field capacity. Irrigation increases from about 1.5 to 2.5 inch per week on sandy
type soils. Water deficits would dramatically increase tuber malformations and sugar-ends.
It can also weaken plants, promoting early blight. Common scab attack is promoted and
the longer the deficit, the greater the attack and more pronounced and enlarge the
blemishes.
Also Efetha (2011) stated that potato is most sensitive to water stress during the
tuber initiation growth stage; therefore, special care should be taken to start irrigating when
soil water in the top half of the root zone (0 to 60-cm depth) is near 70 per cent ofavailable.
This practice increases the number of tubers per plant and applying irrigation just before
. Tuber production of Potato Applied with Different Volumes of Water in La Trinidad,
Benguet | SUMALAG, DAVID I. APRIL 2013
the available soil water is depleted to 70 per cent (i.e. 30 per cent allowable depletion)
during tuber initiation and 65 per cent (i.e. 35 per cent allowable depletion) for other growth
stages, and replenishing available soil water near field capacity in the root zone will greatly
assist in producing a high-quality and high-yielding potato crop. Moreover, according to
Eldredgeet al. (2006), the goal is to ensure that water is available during tuber initiation
and in early tuber development by applying light, frequent irrigation. This method
promotes vigorous growth and replenishes and increases available soil water content in the
entire root zone for later use during the peak water use period, which typically occurs
during the flowering and tuber bulking stage.
At tuber bulking, the canopy and roots are fully grown except for indeterminate
varieties, which have considerably slowed growth. Tubers are 76 to 82% water and this
water must come from the outside, rain or irrigation. Soil moisture should be at 80 to 90%
field capacity. This is the period when plants have their highest demand for water and are
the most sensitive to deficit. Water deficits here will reduce tuber growth but also there
would be increases in tuber malformations, early dying (verticillium and fusarium wilts),
early blight and brown spot and common scab. Water excess increases hollow heart,
swollen lenticels, black leg, late blight and susceptibility to soft rot, leak and pink rot. Slight
moisture stress at this stage will depress yield and this will occur well before any signs
such as a darkening of crop colour or wilting of plants can be seen. More severe stresses at
this stage will affect tuber shape. Stress early in the bulking up stage will cause some tubers
to be pointed like a pear at the stolon end. Stress late in bulking up can cause a point at the
rose end. Growth cracks develop if plants are stressed until the time when skins start to
become firm late in the bulking up phase, then receive plentiful moisture so that the tubers
. Tuber production of Potato Applied with Different Volumes of Water in La Trinidad,
Benguet | SUMALAG, DAVID I. APRIL 2013
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begin to enlarge again (University of Nebraska-Lincoln 2012). Moreover, Shock et al.
2006, soil water should also be maintained between 65 to 100 per cent of available during
the tuber bulking growth stage. Soil water levels outside this desirable range at this growth
stage will reduce marketable tuber yield and contribute to growth deformities (such as
hollow heart, knobbiness, and cracks) and disease development.
During maturity, tuber growth slows and is in the flat stage. As the vine dies, tuber
skin sets, hardens and adheres to the tuber core, irrigation decline during this two to five
weeks period depending on variety and climate. Soil moisture may decline to 60-65% FC.
Excessive irrigation will not only stimulate tuber susceptibility to water rots, soft rot, leak,
and pink rot by swelling lenticels but also form an oxygen deprived environment that
promotes the pathogens to cause this rots. Also too much water will increase tuber
susceptibility to shatter bruise due to raised tuber water content (University of Nebraska-
Lincoln, 2012)
Effect of Water Stress in Potato Production
(King and Stark) The stomata on the leaf close under plant water deficits as defence
against further water loss. The physical indication is an increase in canopy temperature as
a result of reduced evaporative cooling of the leaves. While stomatal closure reduces water
loss through the leaves, it also reduces carbon dioxide diffusion into the leaf. This slows
photosynthesis, reducing the production of photosynthetic products (starch and sugars) by
the plant and their translocation from the leaves to the tubers. Also water deficits reduce
plant growth by reducing the internal water pressure in plant cells (turgor pressure) which
is necessary for expansion. Reduced vine and leaf growth limits total photosynthetic
capacity, while reduced root development limit the plants ability to take up water and
. Tuber production of Potato Applied with Different Volumes of Water in La Trinidad,
Benguet | SUMALAG, DAVID I. APRIL 2013
nutrients. Water deficits disrupt normal tuber growth patterns by reducing or stopping
expansion. Tuber growth resumes following relief of plant water deficits, but the disruption
of the normal tuber expansion rate may result in tuber malformations such as pointed ends,
dumbbells, bottlenecks, and knobs.
Greatest reduction in haulm growth and yield due to moisture stress occurs when
the potato is not irrigated twice for ten days each at the early stages of growth or if subjected
to water stress from the 21st to the 40th day after haulm emergence and suspended irrigation
when the haulm is ten days old appears to enhance greater yield (Bawang, 1981).
Advantages of Proper Irrigation Management
Bawang (1981) recommended that irrigating potato twice a week from planting up
to the 40th day from haulm emergence after which watering will be done once a week will
save labor and water cost without reducing the yield. However, Eldredgeet al. (2006) also
stated that applying irrigation just before the available soil water is depleted to 70 per cent
(i.e. 30 per cent allowable depletion) during tuber initiation and 65 percent (i.e. 35 per cent
allowable depletion) for other growth stages, and replenishing available soil water near
field capacity in the root zone will greatly assist in producing a high-quality and high-
yielding potato crop.
Proper irrigation scheduling also affects pest management strategies. Soil water
decreases the mobility of cutworms and potato tuber moth, protecting the tubers from
attack. Careful irrigation management produces little to no nitrate leaching. In silt loam
soils, it also can reduce nitrogen fertilization requirements (Eldredgeet al., 2006).
Jose (2008) stated that irrigation of potato particularly cultivars agria and reculta
should be done whenever the soil matric potential reaches 25cb to attain physiological,
. Tuber production of Potato Applied with Different Volumes of Water in La Trinidad,
Benguet | SUMALAG, DAVID I. APRIL 2013
growth performance, higher yield and dry matter content, low sugar content, and lesser
tuber disorders. Also plants under moderate stress were noted to have small to medium leaf
area and leaf area index, heaviest roots longest roots and highest relative water content are
obtained in sweet potato (Perey, 2012).
Potatoes are very sensitive to irrigation. Correct irrigation gives yield responses of
around 0.2 tonnes/ha/mm water, which make it highly profitable. Irrigation can also be
managed to minimize or prevent some diseases and to produce tubers of the desired quality
and size required for specific use (Department of Primary Industries, Victoria, Australia,
2012).
. Tuber production of Potato Applied with Different Volumes of Water in La Trinidad,
Benguet | SUMALAG, DAVID I. APRIL 2013
MATERIALS AND METHODS
The experiment was conducted at BSU-Experimental Station in Balili, La Trinidad
Benguet in a greenhouse. Plastic pots with a measurement of 12inches x 15 inches were
used which are filled with silt loam soil and 500gms of compost fertilizer. One seed tuber
was planted per pot at a depth of 4-5 cm. The study was laid out using Completely
Randomized Design (CRD) with 3 replications. Weeding was done to avoid water and
nutrient competition on the crop. At 30 DAE, 500g compost fertilizer was hilled up to
every pot during hilling up at 30 days after emergence. Irrigation was strictly applied right
after emergence where the different volumes of water applied to the different growth stages
served as the treatments.Frequency of irrigation was done every after 3 days.
Code
Treatment
800mlVS-800mlTBS-
800ml of water will be applied from the 1st day of emergence
400mlMS
to 30th day (Vegetative Stage), 800ml at 31st to 75th day
(Tuberization and Bulking Stage) and 400ml at 76th to 90th day
(Maturity Stage)
600mlVS-600mlTBS-
600ml of water will be applied from the 1st day of emergence
300mlMS
to 30th day (Vegetative Stage), 600ml at 31st to 75th day
(Tuberization and Bulking Stage) and 300ml at 76th to 90th day
(Maturity Stage)
400mlVS-400mlTBS-
400ml of water will be applied from the 1st day of emergence
200mlMS
to 30th day (Vegetative Stage), 400ml at 31st to 75th day
(Tuberization and Bulking Stage) and 200ml at 76th to 90th day
(Maturity Stage)
400mlVS-800mlTBS-
400ml of water will be applied from the 1st day of emergence
400mlMS
to 30th day (Vegetative Stage), 800ml at 31st to 75th day
(Tuberization and Bulking Stage) and 400ml at 76th to 90th day
(Maturity Stage)
Data Gathered
. Tuber production of Potato Applied with Different Volumes of Water in La Trinidad,
Benguet | SUMALAG, DAVID I. APRIL 2013
200mlVS-400mlTBS-
200ml of water will be applied from the 1st day of emergence
200mlMS
to 30th day (Vegetative Stage), 400ml at 31st to 75th day
(Tuberization and Bulking Stage) and 200ml at 76th to 90th day
(Maturity Stage)
1. Plant vigor. Plant vigor was noted base on the rating Scale by Palomar and Sanico
(1994).
Scale
Description
Reaction
1
Plants are weak with few stems and leaves;
Poor vigor
very pale
2
Plants are weak with few thin stems and leaves; Less vigorous
pale
3
Plants are better than less vigorous
Moderately vigorous
4
Plants are moderately strong with robust stems Vigorous
5
Plants are strong with robust stems and leaves; Highly vigorous
Light to dark green in colour.
2. Plant survival (%). This was recorded using formula.
Plant survival (%) = No. of plants survived
X 100
No. of plants emerged
3. Initial height. This was measured from the base of the plant at the ground level
to the youngest shoots, using a meter stick from five plant samples in different treatments
at 20 days after emergence.
4. Final height. This was measured from the base of the plant at the ground level to
the youngest shoots, using a meter stick from five plant samples in different treatments at
80 days after emergence.
. Tuber production of Potato Applied with Different Volumes of Water in La Trinidad,
Benguet | SUMALAG, DAVID I. APRIL 2013
5. Root length. This was measured from the base to the tip of the roots using a foot
rule.
6. Number of days to maturity. Days were counted from emergence to maturity
ready for harvesting about 90 % of the haulm is yellowing.
7. Late blight incidence. Late blight was rated using the CIP rating scale (Henfling,
1981).
Score
%Foliage Infected
Description
1
0
0 or very few lesions
3
10
More than 3% but less than 25% foliage
infected
5
50
Half of the foliage infected
7
90
More than 75% but less than 97% infected
9
100
Foliage completely infected
8. Marketable yield (g/plant). Marketable tubers were separated and weighed
during harvest.
9. Non-marketable yield (g/plant). Tubers that were cracked, green and deformed
were separated and weighed during harvest.
10. Total yield (g/plant). This was recorded by getting the total weight of
marketable and non-marketable tubers per plant in the different treatments.
11. Malformed tubers per plant (%). This was recorded using the formula:
Malformed tubers/plant(%) =
No.of malformed tubers
X 100
Total no. of tubers
12. Meteorological Data. The temperature, relative humidity, amount of rainfall and
sunshine duration during the study was taken from La Trinidad, Benguet PAGASA station.
. Tuber production of Potato Applied with Different Volumes of Water in La Trinidad,
Benguet | SUMALAG, DAVID I. APRIL 2013
Data Analysis
The data were statistically analyzed using the analysis of the variance for
completely randomized design (CRD) with 3 replications. The significance of
differencesamong the treatment means will be tested using the Duncan’s Multiple Range
test (DMRT) 5% level of significance.
. Tuber production of Potato Applied with Different Volumes of Water in La Trinidad,
Benguet | SUMALAG, DAVID I. APRIL 2013
RESULTS AND DISCUSSION
Agro- Climatic Data during the Study Period
Table 1 shows the temperature, relative humidity, amount of rainfall and bright
sunshine during the study period. Temperature ranged from 14.25 to 20.28 0C, relative
humidity is 79.81% and bright sunshine in minute range from 121.18 to 360.
The higher the temperature observed inside the green house, causes higher
transpiration rate and evaporation of moisture, thus contributed to water stress of the plants.
Table 1. Agro-climatic data during the study period (November, 2012-February, 2013)
TEMPERATURE
RELATIVE
BRIGHT
MONTH
(0C)
HUMIDITY
SUNSHINE
(%)
(min)
MIN
MAX
NOVEMBER
15.00
27.00
82.00
329.00
DECEMBER
14.00
29.00
75.00
121.18
JANUARY
14.00
26.00
82.00
360.00
FEBRUARY
14.00
27.00
82.00
330.20
MEAN
13.25
27.00
79.81
285.10
. Tuber production of Potato Applied with Different Volumes of Water in La Trinidad,
Benguet | SUMALAG, DAVID I. APRIL 2013
Plant Vigor at 30 DAE and 70 DAE
The different volumes of water did not significantly affect the plant vigor at 35
DAE however, significant at 75 DAE (Table 2). Plants applied with 800 ml and 600 ml
during the tuberization and bulking stage were moderately vigorous. Observation showed
that lesser volumes of water produced plants with poor vigor.
Tisdale and Nelson (1975) stated that changes in the amount required by the plant
may interrupt the normal processes for plant growth such as keeping cells turgid making
stems upright and leaves expanded to receive sunlight for manufacturing and translocation
of carbohydrates and nutrients for growth.
Percent Survival
Table 2 shows that the different volumes of water significantly affected the percent
survival of potato. Plants applied with 400 ml, 300 ml and 200 ml during the early and
vegetative stage had a hundred percent while the lowest survival was recorded in potato
applied with the highest volume of 800 ml.Stem rot was also noted on plants applied with
600ml and 800ml of water. Pereira and Shock (2006) stated that water in excess promotes
high incidence of pests and diseases. Also, University of Nebraska-Lincoln (2012)
postulated that water excess increases black leg, late blight and susceptibility to soft rot,
leak and pink rot.
. Tuber production of Potato Applied with Different Volumes of Water in La Trinidad,
Benguet | SUMALAG, DAVID I. APRIL 2013
Table 2. Plant vigor and percent survival as affected by the different water volumes
PLANT VIGOR
PERCENT
TREATMENT
SURVIVAL
35 DAE
70 DAE
(%)
800mlEVS-800mlTBS-400mlMS
5.0
2.87b
76.19c
600mlEVS-600mlTBS-300mlMS
5.0
2.67b
90.47b
400mlEVS-400mlTBS-200mlMS
5.0
1.40a
100.00a
400mlEVS-800mlTBS-400mlMS
5.0
2.93b
100.00a
200mlEVS-400mlTBS-200mlMS
4.3
1.53a
100.00a
CV (%)
9.54
4.84
Means with the same letter are not significantly different at 5% level of significance
Figure 1. Potato plant that is infected with stem rot during the early vegetative stage
. Tuber production of Potato Applied with Different Volumes of Water in La Trinidad,
Benguet | SUMALAG, DAVID I. APRIL 2013
Initial and Final Plant Height
The application of different volumes of water significantly affected the initial and
final heights of the plants as shown in Table 3. On the initial height, plants applied with
800ml of water during the early vegetative stage produced the tallest plants with a mean of
19.07 cm while the shortest were noted on the plants applied with 200 ml with a mean of
15.07 cm. However, in the final height, plants applied with 800 ml and 600 ml during the
tuberization and bulking had the tallest with a mean of 42.22 to 42.58. While the application
of 400 ml produced shorter plants.
Tisdale and Nelson (1975) revealed that water stress reduces the capacity of
protoplasm to carry on photosynthesis. Also Ajambar (1989) stated that reduce growth and
photosynthesis are both affected by water stress.
Root length
Significant differences were recorded on the potato root length irrigated
withdifferent volumes of water (Table 3). Potato plants applied with the recommended rate
(400mlEVS-800mlTBS-400mlMS) had the longest roots of 28.32 cm.
Water deficiency would inhibit canopy and root growth however an excess would
retard root branching (development) by water-logging root hairs (University of Nebraska-
Lincoln 2012).Moreover, crops in the early vegetative stage may not develop a deep root
system if light watering is done regularly (AVRDC, 1999).
. Tuber production of Potato Applied with Different Volumes of Water in La Trinidad,
Benguet | SUMALAG, DAVID I. APRIL 2013
Table 3. Plant height and root length applied with different volumes of water
HEIGHTS (cm)
ROOT
TREATMENT
LENGTH
20 DAE
90 DAE
(cm)
800mlEVS-800mlTBS-400mlMS
19.07a
42.58a
bc
25.77
600mlEVS-600mlTBS-300mlMS
17.66b
42.22a
b
26.72
400mlEVS-400mlTBS-200mlMS
17.75b
38.82b
bc
25.40
400mlEVS-800mlTBS-400mlMS
17.53b
42.57a
a
28.32
200mlEVS-400mlTBS-200mlMS
15.07c
39.11b
bc
25.79
CV (%)
3.67
3.65
2.26
Means with the same letter are not significantly different at 5% level of significance
Number of Days to Maturity
No significant differences were recorded on the number of days to maturity (Table
4). Plants applied with 400 ml of water during tuberization and bulking stage and 200 ml
of water from bulking to maturity matured earlier at 87 DAE while application of 600 ml-
800 ml during tuberization and bulking stage and 300 ml and 400 ml produced plants that
matured later (90 days). This implies that lesser volumes of water affected the maturity of
plants.
Gabutan (1989) stated that drought affects the total physiological activity through
reduction of the net assimilates, also causes early senescence in potato through shortening
the bulking period and subsequently lowering the yield.
. Tuber production of Potato Applied with Different Volumes of Water in La Trinidad,
Benguet | SUMALAG, DAVID I. APRIL 2013
Table 4. Number of days to maturity as affected by the different volumes of water
TREATMENTS
NO. OF DAYS TO MATURITY
800mlEVS-800mlTBS-400mlMS
90
600mlEVS-600mlTBS-300mlMS
90
400mlEVS-400mlTBS-200mlMS
87
400mlEVS-800mlTBS-400mlMS
90
200mlEVS-400mlTBS-200mlMS
87
CV (%)
Reaction to Late Blight
No significant differences were observed on the late blight incidence as affected by
the different volumes of water. All plants showed slight infection at 60 DAE until harvest.
This could be associated with the method of water application that is directly pouring water
in the soil media that reduced free moisture on the foliage and helped to control the late
blight.
Marketable Yield
As shown in Table 5, the plants applied with different volumes of water at various
growth stages did not significantly affect the weight of marketable tubers per plant.
However, potato plants applied with 600 ml and 800 ml during the tuberization and bulking
stage had the heaviest weight of marketable tubers with a mean ranging from 313.76 to
324.75g per plant. The least was noted on plants applied with 400 ml during tuberization
and bulking stage (268.07g).
. Tuber production of Potato Applied with Different Volumes of Water in La Trinidad,
Benguet | SUMALAG, DAVID I. APRIL 2013
Efetha (2011) stated that potato is most sensitive to water stress during the tuber
initiation growth stage; therefore, start irrigating when soil water in the top half of the root
zone is near 70 per cent ofavailable to assist in producing a high-quality and high-yielding
potato crop. Moreover, Shock et al, (2006) stated that soil water should also be maintained
between 65 to 100 per cent of available water during the tuber bulking stage. Soil water
level outside this desirable range will reduce marketable tuber yield and contribute to
growth deformities and disease development.
Weight of Non- marketable tubers
Table 5 showed that potato plants applied with the different volumes of water
significantly affected the weight of non marketable tubers. Plants irrigated with the
recommended rate and 600mlEVS-600mlTBS-300mlMS produced the lowest non-
marketable tuber of 3.52 and 5.86 g/plant, respectively, while the application of
400mlEVS-400mlTBS-200mlMS, 200mlEVS-400mlTBS-200mlMS (8.94 g) and the
farmers practice had the highest non-marketable tubers.
Tuber quality parameters that are influenced by water stress include tuber grade,
specific gravity, heat necrosis, susceptibility to bruise, hollow heart, translucent-end and
jelly end rot. Tuber grade, as determined by shape, smoothness, and freedom from visible
defects such as growth cracks, dumbbells, and knobs, is highly sensitive to irrigation
management deficiencies (Pereira and Shock, 2006). However, excessive moisture
promotes potato diseases such as tuber-rotting pathogens as cited by some researchers.
. Tuber production of Potato Applied with Different Volumes of Water in La Trinidad,
Benguet | SUMALAG, DAVID I. APRIL 2013
Table 5. Marketable, non-marketable and total yield as affected by the different water
volumes
WEIGHT OF TUBERS
TREATMENT
(g/plant)
MARKET-
NON
TOTAL
ABLE
MARKETABLE
YIELD
800mlEVS-800mlTBS-400mlMS
324.75
8.72a
334.54
600mlEVS-600mlTBS-300mlMS
313.76
5.86b
319.62
400mlEVS-400mlTBS-200mlMS
278.8
9.17a
290.24
400mlEVS-800mlTBS-400mlMS
316.37
3.52b
321.54
200mlEVS-400mlTBS-200mlMS
268.07
8.94a
280.59
CV (%)
13.17
17.85
14.58
Means with the same letter are not significantly different at 5% level of significance
Total Yield of Potato per Plant
There were no significant differences on the total yield of the potato plants
asaffected bythe application of different volumes of water at various growth stages. Mean
total yield ranges from 280.59 to 334.54grm per plant.
Percentage of Malformed Tubers per plant
The different volumes of water did not significantly affect the percentage of
malformed tubers per plant (Table 5). However, plants applied with 400mlEVS-
400mlTBS-200mlMS produced the highest with a mean of 6% followed by 200mlEVS-
400mlTBS-200mlMS with a mean of 5 % while plants applied with the recommended rate
(400mlEVS-400mlTBS-200mlMS) produced the least with a mean of 1.03 %.
(King and Stark, 1997) Reduced root development limit the plants ability to take
up water and nutrients. Water deficits disrupt normal tuber growth patterns by reducing or
. Tuber production of Potato Applied with Different Volumes of Water in La Trinidad,
Benguet | SUMALAG, DAVID I. APRIL 2013
stopping expansion. Tuber growth resumes following relief of plant water deficits, but the
disruption of the normal tuber expansion rate may result in tuber malformations such as
pointed ends, dumbbells, bottlenecks, and knobs.
Table 6.Percentage of malformed tubers per plant as affected by the different volumes of
water
AVERAGE NUMBER OF
MALFORMED
TREATMENT
TUBER / 5 PLANTS
TUBERS
TOTAL
MALFORMED
(%)
800mlEVS-800mlTBS-400mlMS
38.35
1.07
2.80
600mlEVS-600mlTBS-300mlMS
36.65
0.47
1.27
400mlEVS-400mlTBS-200mlMS
30.00
1.80
6.00
400mlEVS-800mlTBS-400mlMS
36.65
0.37
1.03
200mlEVS-400mlTBS-200mlMS
31.65
1.57
4.97
CV (%)
18.05
74.6
Figure 2 . Malformed and cracked tubers more observed on plants applied with lesser
volumes of water
. Tuber production of Potato Applied with Different Volumes of Water in La Trinidad,
Benguet | SUMALAG, DAVID I. APRIL 2013
SUMMARY, CONCLUSION AND RECCOMENDATION
Summary
This study was conducted at BSU Experimental Station in a greenhouse condition
from November 2012 to February 2013 to determine the growth and yield of potato applied
with different volumes of water; best volume of water for potato production and the amount
of water required at various growth stages of potato.
The different volumes of water significantly affected the plant height, root length,
plant vigor at 75 DAE, number of days to maturity, weight of non-marketable tubers and
percent survival of the potato plants. Other data recorded showed no significant
differences.
Application
of
400mlEVS-800mlTBS-400mlMS,
800mlEVS-800mlTBS-
400mlMS and 600mlEVS-600mlTBS-300mlMS produce plants that are taller, more
vigorous and higher yield and normal number of days to mature.
In terms of the plant survival, application of 400mlEVS-800mlTBS-400mlMS,
200mlEVS-400mlTBS-200mlMS and 400mlEVS-400mlTBS-200mlMS had a 100%
survival.
In the root length, longest root is obtained from plants applied with 400mlEVS-
800mlTBS-400mlMS.
Conclusion
Application of 400mlEVS-800mlTBS-400mlMS or the recommended rate shows
more benefit compared to the other treatments as it produced plants with high yield, lesser
. Tuber production of Potato Applied with Different Volumes of Water in La Trinidad,
Benguet | SUMALAG, DAVID I. APRIL 2013
non-marketable tubers, high percentage of survival, more vigorous, longer roots which can
be an advantage in case of water scarcity, and plants with normal time of maturity.
Recommendation
Application of 400mlEVS-800mlTBS-400mlMS per plant is suited for potato
production or 800mlEVS-800mlTBS-400mlMS (farmers practice) could be reduced during
the 1st to 30th DAE on silt loam soils.
Further evaluation is recommended to verify the results of the study under open
field.
. Tuber production of Potato Applied with Different Volumes of Water in La Trinidad,
Benguet | SUMALAG, DAVID I. APRIL 2013
LITERATURE CITED
AJAMBAR, L.D. 1989. Soil Moisture and Water on Plants. New York: McMillan
Publishing Company Inc. Pp. 3-11.
ASIAN VEGETABLE RESEARCH DEVELOPMENT CENTER (AVRDC). 1990.
Vegetable Production Training Manual. Taiwan:AVRDC. Pp. 128-130.
BAWANG, F.T. 1981. The Effect of Moisture Stress on the Growth, Yield, and Some
Postharvest Characteristic of Cultivar Cosima and red Pontiac. M.S Thesis. La
Trinidad, Benguet, Philippines. Benguet State University Pp. ix.
DEPARTMENT OF PRIMARY INDUSTRIES. 2010. Potatoes-Irrigation. Retrieved on
September
18,
2012
from
http://www.dpi.vic.gov.au/agriculture/horticulture/vegetables/potatoes/irrigation-
potatoes.
EFETHA A. 2011. Irrigation Scheduling for Potato in Southern Alberta. Retrieved on
September
2
at
http://www1.agric.gov.ab.ca/$Department/deptdocs.nsf/all/agdex13571.
ELDREDGE E.P., FLOCK R.J., JENSEN L.B., PEREIRA A.B. and C.C. SHOCK. 2006.
Drip Irrigation Guide for Potatoes in the Treasure Valley. U.S. Oregon State
University. Pp.1-8.
GABUTAN, J.D 1989. Physoilogical and Agronomic Comparison Between White Potato
and Sweet Potato in Contrasting Environments of the Philippines. La Trinidad
Benguet Philippines. Benguet State University. Pp. 29-36.
JOSE, D.C. 2008. Soil Moisture Effect on the performance of Potato (Solanumtuberosum)
Cultivars. La Trinidad, Benguet, Philippines. Benguet State University. Pp. 29-36.
KALAW, O.P. 1987. Philippine Potato Production Situation. Agro- Journal. Pp. 12-15.
KRAMER, D. J. 1993. Water Stress Physiology and Plant Growth: Agronomy Journal. Pp.
31-35.
KING, B.A. and J.C STARK. 1997. Potato Irrigation Management. University of Idaho
Cooperative Extension System. Moscow Idaho U.S. Pp. 1-4.
MUMNS S.R and C.J PEARSON. 1995. Effect of Water Deficit on Translocation of
Carbohydrates in Solanumtuberosum. Australian Journal of Plant Physiology.
Accessed at www.publish.csrio.au/?act=viewfile&fileid=pp9740529.pdf.
. Tuber production of Potato Applied with Different Volumes of Water in La Trinidad,
Benguet | SUMALAG, DAVID I. APRIL 2013
NORTHERN PHILIPPINES ROOT CROP RESEARCH AND TRAINING CENTER
(NPRCRTC). 1999. Potato Production Guide. La Trinidad, Benguet: Benguet state
University. Pp 1-2.
NORTHERN PHILIPPINES ROOT CROP RESEARCH AND TRAINING CENTER
(NPRCRTC). 1999. Potato Production Guide. La TrinnidadBenguet: Benguet State
University. Pp. 1-2.
PEREIRA, A.C and C.C SHOCK. 2006. Development of irrigation best management
practices for potato from a research perspective in the United States. Sakia.org e-
publish. Pp. 1-20.
PEREY A.C. 2012. Screening and Evaluation of Sweet Potato Genotypes for Water Stress
Resistance. La Trinidad, Benguet, Philippines. Benguet State University. Pp. ix.
ROWE, R.C AND G.A SECOR. 1993. Managing Potato Health from Emergence to
Harvest: The American Phytopathological Society. Wooster, Ohio.ASP Press
Pp.35-40.
TISDALE, S.C and W.L. NELSON. 1975. Soil Fertility and Fertilizers. New York:
McMillan Publishing Company Inc. Pp. 29-30.
UNIVERSITY OF NEBRASKA-LINCOLN, 2012. CropWatch: Potato Education Guide,
Potato Growth and Irrigation Scheduling. Retrieved on September 20, 2012 from
http://cropwatch.unl.edu/web/potato/plant_growth.
. Tuber production of Potato Applied with Different Volumes of Water in La Trinidad,
Benguet | SUMALAG, DAVID I. APRIL 2013
SUMALAG, DAVID I. APRIL 2013. Tuber production of Potato Applied with
Different Volumes of Water in La Trinidad, Benguet. Benguet State University, La
Trinidad Benguet.
Adviser: Janet P. Pablo, Msc.
ABSTRACT
The study was conducted to determine the growth and yield of potato applied with
different volumes of water;determine the best volume of water for potato production; and
to determine the amount of water required at various growth stages of potato.
The different volumes of water applied on the different growth stages significantly
affected the plant height, root length, plant vigor at 75DAE, weight of non-marketable
tubers and percent survival of the potato plants.
Potato plants applied with 400ml of water during early vegetative stage, 800ml at
tuberization to bulking stage and 400ml during the maturity stage per plant produced high
percentage of survival, more vigorous plants, high yield, lesser non-marketable tubers,
longer roots and lesser malformed tubers as compared to the farmer’s practice of800ml of
water during early vegetative stage, 800ml at tuberization to bulking stage and 400ml
during the maturity stage.
. Tuber production of Potato Applied with Different Volumes of Water in La Trinidad,
Benguet | SUMALAG, DAVID I. APRIL 2013
INTRODUCTION
Potato has a great role in the agriculture economy aside from being nutritious.
Higher income and production is attained in potato production in a shorter period of time
compared to rice production. Also price and demand for potato are more stable as compared
to other cash crop vegetables where price fluctuation is very high (NPRCRTC, 1999).
According to Pereira et al. (2006) using optimal irrigation strategies with potato
can mean a healthy crop with high marketable yield potential. Growers are encouraged to
properly manage irrigation by regularly monitoring soil water to ensure that the availability
of water does not become a limiting factor in producing a high-yielding potato crop. Also,
ensure that the potato crop is well-fertilized and well-protected from pests.
In the Philippines, Benguet and Mountain Province are the major producers of
potato (Kalaw, 1987) and irrigation is one of the problems meet because production time
is within the dry months wherein availability of water is limited.
At present, excessive and deficit application of water in irrigation is one factor
which limits the production of potato in Benguet and other production areas.
As stated by the Department of Primary Industries in Victoria, Australia (2010)
potatoes are very sensitive to irrigation. Correct irrigation gives yield responses of around
0.2 tonnes/ha/mm water, which make it highly profitable. Irrigation can also be managed
to minimize or prevent some diseases and to produce tubers of the desired quality and size
required for specific use. In this case, there is a need to determine the best water
requirements of potato at various growth stages which will be useful for successful potato
production which this study aims.
. Tuber production of Potato Applied with Different Volumes of Water in La Trinidad,
Benguet | SUMALAG, DAVID I. APRIL 2013
2
In addition, with the climatic change, erratic frequencies of drought and flooding is
experienced globally, thus, water management is important to study in irrigation sensitive
crops such as potato.
This study was conducted to:
1. determine the growth and yield of potato applied with different volumes of water;
2. determine the best volume of water for potato production; and,
3. determine the amount of water required at various growth stages of potato.
The study was conducted at Benguet State University Experimental Station, Balili
La Trinidad, Benguet from November 2012 to February 2013.
. Tuber production of Potato Applied with Different Volumes of Water in La Trinidad,
Benguet | SUMALAG, DAVID I. APRIL 2013
REVIEW OF LITERATURE
Effect of Water Stress on Plant
Kramer (1993) stated that water stress affects the aspects of plant growth pertaining
to the anatomy, morphology, physiology and biochemistry. So changes in the amount
required by the plant may interrupt the normal processes for plant growth such as; keeping
cells turgid making stems upright and leaves expanded to receive sunlight for
manufacturing and translocation of carbohydrates and nutrients for growth (Tisdale and
Nelson,1975); water stress reduces the capacity of protoplasm to carry on photosynthesis,
and reduce growth and photosynthesis are both affected by water stress (Ajambar, 1989);
Mumns and Pearson (1995) stated that water deficit causes low leaf water potentials
leading to decrease in translocation of carbon which is proportional to the decline in
photosynthesis and Gabutan (1989) stated that drought affects the total physiological
activity through reduction of the net assimilates, also causes early senescence in potato
through shortening the bulking period and subsequently lowering the yield.
In addition, water stress may lead to decrease in stomatal opening and lose of
turgidity in the guard cells. Eventually, the rate of photosynthesis and consequently growth
and yield also decrease where the plant may wilt or die in extreme condition. Moreover,
under excess water condition, plant growth is being toxified, and finally retards growth of
the plant. It is also said that crops in the early vegetative stage may not develop a deep root
system if light watering is done regularly. Also, excessive water affects crop growth as it
causes damages to shoots, high incidence of pests and diseases, physical destruction of
flowers and less activity of pollinators (AVRDC, 1990).
. Tuber production of Potato Applied with Different Volumes of Water in La Trinidad,
Benguet | SUMALAG, DAVID I. APRIL 2013
Irrigation in Potato Production
Irrigation in the era of “best management practices” requires the simultaneous
achievement of effective water use for profitable production and environmental protection.
Irrigation in excess of crop use should be minimized due to the risk of leaching of nitrate
and pesticide residues towards groundwater and the risk of runoff losses of sediment and
nutrients to surface water. Excessive irrigation promotes potato diseases. Yet potato is a
shallow rooted, water stress sensitive crop. Water deficits reduce tuber yields and quality.
Tuber quality parameters that are influenced by water stress include tuber grade, specific
gravity, heat necrosis, susceptibility to bruise, hollow heart, translucent-end, jelly end rot,
and the dark colour of fried strips and chips. Tuber grade, as determined by shape,
smoothness, and freedom from visible defects such as growth cracks, dumbbells, and
knobs, is highly sensitive to irrigation management deficiencies. Together these tuber
responses to deficit irrigation make potato a challenging crop to irrigate (Pereira and Shock,
2006).
Under irrigation leads to losses in tuber quality, market grade, total yield, and
contract price. However, over irrigation leads to erosion, disease susceptibility, water loss,
extra energy costs for pumping, nitrogen leaching, and increased in crop nitrogen needs.
Excessively wet soil is conducive to many tuber rotting pathogens, encouraging the
incidence of blights, rots, and wilts that can limit yield, tuber quality, tuber size, tuber dry
matter content, and crop marketability at harvest or from storage. Dense canopy growth,
long periods of leaf wetness, and high relative humidity creates microenvironments that
favour infection. Improperly managed irrigation often keeps the vines wet for long periods
of time, exacerbating the risk of infection (Eldredgeet al., 2006).
. Tuber production of Potato Applied with Different Volumes of Water in La Trinidad,
Benguet | SUMALAG, DAVID I. APRIL 2013
Irrigation management affects disease severity and management. The increased
humidity from irrigation will have greater effects where the macroclimate is humid or sub-
humid and be of less importance where it is drier. For potato grown in hot areas, sprinkler
irrigation can cool the environment, with possible reductions in physiological defects.
However, different irrigation methods can contribute to the occurrence of diseases and
pests on the crop depending on site-specific weather pattern. Wet soil is conducive to most
tuber-rotting pathogens. Excessive soil moisture following planting can promote seed piece
decay and an erratic emergence. Excessive irrigation can also erode hills, thus exposing
shallow-set tubers to greening or sunscald and infection by early and late blight pathogens
(Rowe and Secor, 1993).
Potato needs to have adequate and consistent soil water during most of its growth
stages: sprouting, vegetative, tuber initiation (tuber set), tuber bulking, and maturation
growth stages. However, excessively wet soil is conducive to many tuber-rotting
pathogens, and excessive moisture on the crop canopy encourages the incidence of foliar
blights and wilts that can limit potato performance. Also yield reductions due to over
irrigation can be attributed to poor soil aeration, increase susceptibility to rots and diseases,
and leaching of nitrogen from the shallow root zone (Eldredgeet al., 2006).
Irrigation Requirement in Potato Growth Stages
From emergence to tuber initiation, roots are in the second half of their growth.
During this period, the vine grows very rapidly, as much as doubling the canopy every
week. With rapidly increasing foliage every week, irrigation starts low, 0.5 inches of
irrigation is applied. At tuber initiation, about three weeks after emergence depending on
variety, seed health, weather, soil, and cultural practices used, about 1.5 inches of irrigation
. Tuber production of Potato Applied with Different Volumes of Water in La Trinidad,
Benguet | SUMALAG, DAVID I. APRIL 2013
is applied. A soil moisture of 70 to 80% is preferred, less than 65% field capacity would
be considered a deficit. Water deficiency at this point would inhibit canopy and root
growth, and indirectly weed control by less ground cover. An excess would retard root
branching (development) by water-logging root hairs and promote nitrogen leaching. In
short, with an increase in foliage and thereby transpiration, irrigation should begin
gradually increase as the canopy grows (University of Nebraska-Lincoln 2012). Also,
Water use rates for potato begin at about 0.4 mm per day when the crop sprouts (emerges)
and increase to as high as 7 mm per day when the potato canopy completely shades the
ground and tubers are bulking. Potato water demand decreases as the crop achieves full
tuber bulking and maturation (Efetha, 2011).
According to the University of Nebraska-Lincoln (2012) during tuberization, the
first set of tubers is being initiated and these are in slow growth, development stage, the
lag phase of tuber growth. Irrigation becomes increasingly important and water stress
becomes less tolerable. Transpiration reaches its highest rate. Optimal soil moisture is 80
to 90% field capacity. Irrigation increases from about 1.5 to 2.5 inch per week on sandy
type soils. Water deficits would dramatically increase tuber malformations and sugar-ends.
It can also weaken plants, promoting early blight. Common scab attack is promoted and
the longer the deficit, the greater the attack and more pronounced and enlarge the
blemishes.
Also Efetha (2011) stated that potato is most sensitive to water stress during the
tuber initiation growth stage; therefore, special care should be taken to start irrigating when
soil water in the top half of the root zone (0 to 60-cm depth) is near 70 per cent ofavailable.
This practice increases the number of tubers per plant and applying irrigation just before
. Tuber production of Potato Applied with Different Volumes of Water in La Trinidad,
Benguet | SUMALAG, DAVID I. APRIL 2013
the available soil water is depleted to 70 per cent (i.e. 30 per cent allowable depletion)
during tuber initiation and 65 per cent (i.e. 35 per cent allowable depletion) for other growth
stages, and replenishing available soil water near field capacity in the root zone will greatly
assist in producing a high-quality and high-yielding potato crop. Moreover, according to
Eldredgeet al. (2006), the goal is to ensure that water is available during tuber initiation
and in early tuber development by applying light, frequent irrigation. This method
promotes vigorous growth and replenishes and increases available soil water content in the
entire root zone for later use during the peak water use period, which typically occurs
during the flowering and tuber bulking stage.
At tuber bulking, the canopy and roots are fully grown except for indeterminate
varieties, which have considerably slowed growth. Tubers are 76 to 82% water and this
water must come from the outside, rain or irrigation. Soil moisture should be at 80 to 90%
field capacity. This is the period when plants have their highest demand for water and are
the most sensitive to deficit. Water deficits here will reduce tuber growth but also there
would be increases in tuber malformations, early dying (verticillium and fusarium wilts),
early blight and brown spot and common scab. Water excess increases hollow heart,
swollen lenticels, black leg, late blight and susceptibility to soft rot, leak and pink rot. Slight
moisture stress at this stage will depress yield and this will occur well before any signs
such as a darkening of crop colour or wilting of plants can be seen. More severe stresses at
this stage will affect tuber shape. Stress early in the bulking up stage will cause some tubers
to be pointed like a pear at the stolon end. Stress late in bulking up can cause a point at the
rose end. Growth cracks develop if plants are stressed until the time when skins start to
become firm late in the bulking up phase, then receive plentiful moisture so that the tubers
. Tuber production of Potato Applied with Different Volumes of Water in La Trinidad,
Benguet | SUMALAG, DAVID I. APRIL 2013
8
8
begin to enlarge again (University of Nebraska-Lincoln 2012). Moreover, Shock et al.
2006, soil water should also be maintained between 65 to 100 per cent of available during
the tuber bulking growth stage. Soil water levels outside this desirable range at this growth
stage will reduce marketable tuber yield and contribute to growth deformities (such as
hollow heart, knobbiness, and cracks) and disease development.
During maturity, tuber growth slows and is in the flat stage. As the vine dies, tuber
skin sets, hardens and adheres to the tuber core, irrigation decline during this two to five
weeks period depending on variety and climate. Soil moisture may decline to 60-65% FC.
Excessive irrigation will not only stimulate tuber susceptibility to water rots, soft rot, leak,
and pink rot by swelling lenticels but also form an oxygen deprived environment that
promotes the pathogens to cause this rots. Also too much water will increase tuber
susceptibility to shatter bruise due to raised tuber water content (University of Nebraska-
Lincoln, 2012)
Effect of Water Stress in Potato Production
(King and Stark) The stomata on the leaf close under plant water deficits as defence
against further water loss. The physical indication is an increase in canopy temperature as
a result of reduced evaporative cooling of the leaves. While stomatal closure reduces water
loss through the leaves, it also reduces carbon dioxide diffusion into the leaf. This slows
photosynthesis, reducing the production of photosynthetic products (starch and sugars) by
the plant and their translocation from the leaves to the tubers. Also water deficits reduce
plant growth by reducing the internal water pressure in plant cells (turgor pressure) which
is necessary for expansion. Reduced vine and leaf growth limits total photosynthetic
capacity, while reduced root development limit the plants ability to take up water and
. Tuber production of Potato Applied with Different Volumes of Water in La Trinidad,
Benguet | SUMALAG, DAVID I. APRIL 2013
nutrients. Water deficits disrupt normal tuber growth patterns by reducing or stopping
expansion. Tuber growth resumes following relief of plant water deficits, but the disruption
of the normal tuber expansion rate may result in tuber malformations such as pointed ends,
dumbbells, bottlenecks, and knobs.
Greatest reduction in haulm growth and yield due to moisture stress occurs when
the potato is not irrigated twice for ten days each at the early stages of growth or if subjected
to water stress from the 21st to the 40th day after haulm emergence and suspended irrigation
when the haulm is ten days old appears to enhance greater yield (Bawang, 1981).
Advantages of Proper Irrigation Management
Bawang (1981) recommended that irrigating potato twice a week from planting up
to the 40th day from haulm emergence after which watering will be done once a week will
save labor and water cost without reducing the yield. However, Eldredgeet al. (2006) also
stated that applying irrigation just before the available soil water is depleted to 70 per cent
(i.e. 30 per cent allowable depletion) during tuber initiation and 65 percent (i.e. 35 per cent
allowable depletion) for other growth stages, and replenishing available soil water near
field capacity in the root zone will greatly assist in producing a high-quality and high-
yielding potato crop.
Proper irrigation scheduling also affects pest management strategies. Soil water
decreases the mobility of cutworms and potato tuber moth, protecting the tubers from
attack. Careful irrigation management produces little to no nitrate leaching. In silt loam
soils, it also can reduce nitrogen fertilization requirements (Eldredgeet al., 2006).
Jose (2008) stated that irrigation of potato particularly cultivars agria and reculta
should be done whenever the soil matric potential reaches 25cb to attain physiological,
. Tuber production of Potato Applied with Different Volumes of Water in La Trinidad,
Benguet | SUMALAG, DAVID I. APRIL 2013
growth performance, higher yield and dry matter content, low sugar content, and lesser
tuber disorders. Also plants under moderate stress were noted to have small to medium leaf
area and leaf area index, heaviest roots longest roots and highest relative water content are
obtained in sweet potato (Perey, 2012).
Potatoes are very sensitive to irrigation. Correct irrigation gives yield responses of
around 0.2 tonnes/ha/mm water, which make it highly profitable. Irrigation can also be
managed to minimize or prevent some diseases and to produce tubers of the desired quality
and size required for specific use (Department of Primary Industries, Victoria, Australia,
2012).
. Tuber production of Potato Applied with Different Volumes of Water in La Trinidad,
Benguet | SUMALAG, DAVID I. APRIL 2013
MATERIALS AND METHODS
The experiment was conducted at BSU-Experimental Station in Balili, La Trinidad
Benguet in a greenhouse. Plastic pots with a measurement of 12inches x 15 inches were
used which are filled with silt loam soil and 500gms of compost fertilizer. One seed tuber
was planted per pot at a depth of 4-5 cm. The study was laid out using Completely
Randomized Design (CRD) with 3 replications. Weeding was done to avoid water and
nutrient competition on the crop. At 30 DAE, 500g compost fertilizer was hilled up to
every pot during hilling up at 30 days after emergence. Irrigation was strictly applied right
after emergence where the different volumes of water applied to the different growth stages
served as the treatments.Frequency of irrigation was done every after 3 days.
Code
Treatment
800mlVS-800mlTBS-
800ml of water will be applied from the 1st day of emergence
400mlMS
to 30th day (Vegetative Stage), 800ml at 31st to 75th day
(Tuberization and Bulking Stage) and 400ml at 76th to 90th day
(Maturity Stage)
600mlVS-600mlTBS-
600ml of water will be applied from the 1st day of emergence
300mlMS
to 30th day (Vegetative Stage), 600ml at 31st to 75th day
(Tuberization and Bulking Stage) and 300ml at 76th to 90th day
(Maturity Stage)
400mlVS-400mlTBS-
400ml of water will be applied from the 1st day of emergence
200mlMS
to 30th day (Vegetative Stage), 400ml at 31st to 75th day
(Tuberization and Bulking Stage) and 200ml at 76th to 90th day
(Maturity Stage)
400mlVS-800mlTBS-
400ml of water will be applied from the 1st day of emergence
400mlMS
to 30th day (Vegetative Stage), 800ml at 31st to 75th day
(Tuberization and Bulking Stage) and 400ml at 76th to 90th day
(Maturity Stage)
Data Gathered
. Tuber production of Potato Applied with Different Volumes of Water in La Trinidad,
Benguet | SUMALAG, DAVID I. APRIL 2013
200mlVS-400mlTBS-
200ml of water will be applied from the 1st day of emergence
200mlMS
to 30th day (Vegetative Stage), 400ml at 31st to 75th day
(Tuberization and Bulking Stage) and 200ml at 76th to 90th day
(Maturity Stage)
1. Plant vigor. Plant vigor was noted base on the rating Scale by Palomar and Sanico
(1994).
Scale
Description
Reaction
1
Plants are weak with few stems and leaves;
Poor vigor
very pale
2
Plants are weak with few thin stems and leaves; Less vigorous
pale
3
Plants are better than less vigorous
Moderately vigorous
4
Plants are moderately strong with robust stems Vigorous
5
Plants are strong with robust stems and leaves; Highly vigorous
Light to dark green in colour.
2. Plant survival (%). This was recorded using formula.
Plant survival (%) = No. of plants survived
X 100
No. of plants emerged
3. Initial height. This was measured from the base of the plant at the ground level
to the youngest shoots, using a meter stick from five plant samples in different treatments
at 20 days after emergence.
4. Final height. This was measured from the base of the plant at the ground level to
the youngest shoots, using a meter stick from five plant samples in different treatments at
80 days after emergence.
. Tuber production of Potato Applied with Different Volumes of Water in La Trinidad,
Benguet | SUMALAG, DAVID I. APRIL 2013
5. Root length. This was measured from the base to the tip of the roots using a foot
rule.
6. Number of days to maturity. Days were counted from emergence to maturity
ready for harvesting about 90 % of the haulm is yellowing.
7. Late blight incidence. Late blight was rated using the CIP rating scale (Henfling,
1981).
Score
%Foliage Infected
Description
1
0
0 or very few lesions
3
10
More than 3% but less than 25% foliage
infected
5
50
Half of the foliage infected
7
90
More than 75% but less than 97% infected
9
100
Foliage completely infected
8. Marketable yield (g/plant). Marketable tubers were separated and weighed
during harvest.
9. Non-marketable yield (g/plant). Tubers that were cracked, green and deformed
were separated and weighed during harvest.
10. Total yield (g/plant). This was recorded by getting the total weight of
marketable and non-marketable tubers per plant in the different treatments.
11. Malformed tubers per plant (%). This was recorded using the formula:
Malformed tubers/plant(%) =
No.of malformed tubers
X 100
Total no. of tubers
12. Meteorological Data. The temperature, relative humidity, amount of rainfall and
sunshine duration during the study was taken from La Trinidad, Benguet PAGASA station.
. Tuber production of Potato Applied with Different Volumes of Water in La Trinidad,
Benguet | SUMALAG, DAVID I. APRIL 2013
Data Analysis
The data were statistically analyzed using the analysis of the variance for
completely randomized design (CRD) with 3 replications. The significance of
differencesamong the treatment means will be tested using the Duncan’s Multiple Range
test (DMRT) 5% level of significance.
. Tuber production of Potato Applied with Different Volumes of Water in La Trinidad,
Benguet | SUMALAG, DAVID I. APRIL 2013
RESULTS AND DISCUSSION
Agro- Climatic Data during the Study Period
Table 1 shows the temperature, relative humidity, amount of rainfall and bright
sunshine during the study period. Temperature ranged from 14.25 to 20.28 0C, relative
humidity is 79.81% and bright sunshine in minute range from 121.18 to 360.
The higher the temperature observed inside the green house, causes higher
transpiration rate and evaporation of moisture, thus contributed to water stress of the plants.
Table 1. Agro-climatic data during the study period (November, 2012-February, 2013)
TEMPERATURE
RELATIVE
BRIGHT
MONTH
(0C)
HUMIDITY
SUNSHINE
(%)
(min)
MIN
MAX
NOVEMBER
15.00
27.00
82.00
329.00
DECEMBER
14.00
29.00
75.00
121.18
JANUARY
14.00
26.00
82.00
360.00
FEBRUARY
14.00
27.00
82.00
330.20
MEAN
13.25
27.00
79.81
285.10
. Tuber production of Potato Applied with Different Volumes of Water in La Trinidad,
Benguet | SUMALAG, DAVID I. APRIL 2013
Plant Vigor at 30 DAE and 70 DAE
The different volumes of water did not significantly affect the plant vigor at 35
DAE however, significant at 75 DAE (Table 2). Plants applied with 800 ml and 600 ml
during the tuberization and bulking stage were moderately vigorous. Observation showed
that lesser volumes of water produced plants with poor vigor.
Tisdale and Nelson (1975) stated that changes in the amount required by the plant
may interrupt the normal processes for plant growth such as keeping cells turgid making
stems upright and leaves expanded to receive sunlight for manufacturing and translocation
of carbohydrates and nutrients for growth.
Percent Survival
Table 2 shows that the different volumes of water significantly affected the percent
survival of potato. Plants applied with 400 ml, 300 ml and 200 ml during the early and
vegetative stage had a hundred percent while the lowest survival was recorded in potato
applied with the highest volume of 800 ml.Stem rot was also noted on plants applied with
600ml and 800ml of water. Pereira and Shock (2006) stated that water in excess promotes
high incidence of pests and diseases. Also, University of Nebraska-Lincoln (2012)
postulated that water excess increases black leg, late blight and susceptibility to soft rot,
leak and pink rot.
. Tuber production of Potato Applied with Different Volumes of Water in La Trinidad,
Benguet | SUMALAG, DAVID I. APRIL 2013
Table 2. Plant vigor and percent survival as affected by the different water volumes
PLANT VIGOR
PERCENT
TREATMENT
SURVIVAL
35 DAE
70 DAE
(%)
800mlEVS-800mlTBS-400mlMS
5.0
2.87b
76.19c
600mlEVS-600mlTBS-300mlMS
5.0
2.67b
90.47b
400mlEVS-400mlTBS-200mlMS
5.0
1.40a
100.00a
400mlEVS-800mlTBS-400mlMS
5.0
2.93b
100.00a
200mlEVS-400mlTBS-200mlMS
4.3
1.53a
100.00a
CV (%)
9.54
4.84
Means with the same letter are not significantly different at 5% level of significance
Figure 1. Potato plant that is infected with stem rot during the early vegetative stage
. Tuber production of Potato Applied with Different Volumes of Water in La Trinidad,
Benguet | SUMALAG, DAVID I. APRIL 2013
Initial and Final Plant Height
The application of different volumes of water significantly affected the initial and
final heights of the plants as shown in Table 3. On the initial height, plants applied with
800ml of water during the early vegetative stage produced the tallest plants with a mean of
19.07 cm while the shortest were noted on the plants applied with 200 ml with a mean of
15.07 cm. However, in the final height, plants applied with 800 ml and 600 ml during the
tuberization and bulking had the tallest with a mean of 42.22 to 42.58. While the application
of 400 ml produced shorter plants.
Tisdale and Nelson (1975) revealed that water stress reduces the capacity of
protoplasm to carry on photosynthesis. Also Ajambar (1989) stated that reduce growth and
photosynthesis are both affected by water stress.
Root length
Significant differences were recorded on the potato root length irrigated
withdifferent volumes of water (Table 3). Potato plants applied with the recommended rate
(400mlEVS-800mlTBS-400mlMS) had the longest roots of 28.32 cm.
Water deficiency would inhibit canopy and root growth however an excess would
retard root branching (development) by water-logging root hairs (University of Nebraska-
Lincoln 2012).Moreover, crops in the early vegetative stage may not develop a deep root
system if light watering is done regularly (AVRDC, 1999).
. Tuber production of Potato Applied with Different Volumes of Water in La Trinidad,
Benguet | SUMALAG, DAVID I. APRIL 2013
Table 3. Plant height and root length applied with different volumes of water
HEIGHTS (cm)
ROOT
TREATMENT
LENGTH
20 DAE
90 DAE
(cm)
800mlEVS-800mlTBS-400mlMS
19.07a
42.58a
bc
25.77
600mlEVS-600mlTBS-300mlMS
17.66b
42.22a
b
26.72
400mlEVS-400mlTBS-200mlMS
17.75b
38.82b
bc
25.40
400mlEVS-800mlTBS-400mlMS
17.53b
42.57a
a
28.32
200mlEVS-400mlTBS-200mlMS
15.07c
39.11b
bc
25.79
CV (%)
3.67
3.65
2.26
Means with the same letter are not significantly different at 5% level of significance
Number of Days to Maturity
No significant differences were recorded on the number of days to maturity (Table
4). Plants applied with 400 ml of water during tuberization and bulking stage and 200 ml
of water from bulking to maturity matured earlier at 87 DAE while application of 600 ml-
800 ml during tuberization and bulking stage and 300 ml and 400 ml produced plants that
matured later (90 days). This implies that lesser volumes of water affected the maturity of
plants.
Gabutan (1989) stated that drought affects the total physiological activity through
reduction of the net assimilates, also causes early senescence in potato through shortening
the bulking period and subsequently lowering the yield.
. Tuber production of Potato Applied with Different Volumes of Water in La Trinidad,
Benguet | SUMALAG, DAVID I. APRIL 2013
Table 4. Number of days to maturity as affected by the different volumes of water
TREATMENTS
NO. OF DAYS TO MATURITY
800mlEVS-800mlTBS-400mlMS
90
600mlEVS-600mlTBS-300mlMS
90
400mlEVS-400mlTBS-200mlMS
87
400mlEVS-800mlTBS-400mlMS
90
200mlEVS-400mlTBS-200mlMS
87
CV (%)
Reaction to Late Blight
No significant differences were observed on the late blight incidence as affected by
the different volumes of water. All plants showed slight infection at 60 DAE until harvest.
This could be associated with the method of water application that is directly pouring water
in the soil media that reduced free moisture on the foliage and helped to control the late
blight.
Marketable Yield
As shown in Table 5, the plants applied with different volumes of water at various
growth stages did not significantly affect the weight of marketable tubers per plant.
However, potato plants applied with 600 ml and 800 ml during the tuberization and bulking
stage had the heaviest weight of marketable tubers with a mean ranging from 313.76 to
324.75g per plant. The least was noted on plants applied with 400 ml during tuberization
and bulking stage (268.07g).
. Tuber production of Potato Applied with Different Volumes of Water in La Trinidad,
Benguet | SUMALAG, DAVID I. APRIL 2013
Efetha (2011) stated that potato is most sensitive to water stress during the tuber
initiation growth stage; therefore, start irrigating when soil water in the top half of the root
zone is near 70 per cent ofavailable to assist in producing a high-quality and high-yielding
potato crop. Moreover, Shock et al, (2006) stated that soil water should also be maintained
between 65 to 100 per cent of available water during the tuber bulking stage. Soil water
level outside this desirable range will reduce marketable tuber yield and contribute to
growth deformities and disease development.
Weight of Non- marketable tubers
Table 5 showed that potato plants applied with the different volumes of water
significantly affected the weight of non marketable tubers. Plants irrigated with the
recommended rate and 600mlEVS-600mlTBS-300mlMS produced the lowest non-
marketable tuber of 3.52 and 5.86 g/plant, respectively, while the application of
400mlEVS-400mlTBS-200mlMS, 200mlEVS-400mlTBS-200mlMS (8.94 g) and the
farmers practice had the highest non-marketable tubers.
Tuber quality parameters that are influenced by water stress include tuber grade,
specific gravity, heat necrosis, susceptibility to bruise, hollow heart, translucent-end and
jelly end rot. Tuber grade, as determined by shape, smoothness, and freedom from visible
defects such as growth cracks, dumbbells, and knobs, is highly sensitive to irrigation
management deficiencies (Pereira and Shock, 2006). However, excessive moisture
promotes potato diseases such as tuber-rotting pathogens as cited by some researchers.
. Tuber production of Potato Applied with Different Volumes of Water in La Trinidad,
Benguet | SUMALAG, DAVID I. APRIL 2013
Table 5. Marketable, non-marketable and total yield as affected by the different water
volumes
WEIGHT OF TUBERS
TREATMENT
(g/plant)
MARKET-
NON
TOTAL
ABLE
MARKETABLE
YIELD
800mlEVS-800mlTBS-400mlMS
324.75
8.72a
334.54
600mlEVS-600mlTBS-300mlMS
313.76
5.86b
319.62
400mlEVS-400mlTBS-200mlMS
278.8
9.17a
290.24
400mlEVS-800mlTBS-400mlMS
316.37
3.52b
321.54
200mlEVS-400mlTBS-200mlMS
268.07
8.94a
280.59
CV (%)
13.17
17.85
14.58
Means with the same letter are not significantly different at 5% level of significance
Total Yield of Potato per Plant
There were no significant differences on the total yield of the potato plants
asaffected bythe application of different volumes of water at various growth stages. Mean
total yield ranges from 280.59 to 334.54grm per plant.
Percentage of Malformed Tubers per plant
The different volumes of water did not significantly affect the percentage of
malformed tubers per plant (Table 5). However, plants applied with 400mlEVS-
400mlTBS-200mlMS produced the highest with a mean of 6% followed by 200mlEVS-
400mlTBS-200mlMS with a mean of 5 % while plants applied with the recommended rate
(400mlEVS-400mlTBS-200mlMS) produced the least with a mean of 1.03 %.
(King and Stark, 1997) Reduced root development limit the plants ability to take
up water and nutrients. Water deficits disrupt normal tuber growth patterns by reducing or
. Tuber production of Potato Applied with Different Volumes of Water in La Trinidad,
Benguet | SUMALAG, DAVID I. APRIL 2013
stopping expansion. Tuber growth resumes following relief of plant water deficits, but the
disruption of the normal tuber expansion rate may result in tuber malformations such as
pointed ends, dumbbells, bottlenecks, and knobs.
Table 6.Percentage of malformed tubers per plant as affected by the different volumes of
water
AVERAGE NUMBER OF
MALFORMED
TREATMENT
TUBER / 5 PLANTS
TUBERS
TOTAL
MALFORMED
(%)
800mlEVS-800mlTBS-400mlMS
38.35
1.07
2.80
600mlEVS-600mlTBS-300mlMS
36.65
0.47
1.27
400mlEVS-400mlTBS-200mlMS
30.00
1.80
6.00
400mlEVS-800mlTBS-400mlMS
36.65
0.37
1.03
200mlEVS-400mlTBS-200mlMS
31.65
1.57
4.97
CV (%)
18.05
74.6
Figure 2 . Malformed and cracked tubers more observed on plants applied with lesser
volumes of water
. Tuber production of Potato Applied with Different Volumes of Water in La Trinidad,
Benguet | SUMALAG, DAVID I. APRIL 2013
SUMMARY, CONCLUSION AND RECCOMENDATION
Summary
This study was conducted at BSU Experimental Station in a greenhouse condition
from November 2012 to February 2013 to determine the growth and yield of potato applied
with different volumes of water; best volume of water for potato production and the amount
of water required at various growth stages of potato.
The different volumes of water significantly affected the plant height, root length,
plant vigor at 75 DAE, number of days to maturity, weight of non-marketable tubers and
percent survival of the potato plants. Other data recorded showed no significant
differences.
Application
of
400mlEVS-800mlTBS-400mlMS,
800mlEVS-800mlTBS-
400mlMS and 600mlEVS-600mlTBS-300mlMS produce plants that are taller, more
vigorous and higher yield and normal number of days to mature.
In terms of the plant survival, application of 400mlEVS-800mlTBS-400mlMS,
200mlEVS-400mlTBS-200mlMS and 400mlEVS-400mlTBS-200mlMS had a 100%
survival.
In the root length, longest root is obtained from plants applied with 400mlEVS-
800mlTBS-400mlMS.
Conclusion
Application of 400mlEVS-800mlTBS-400mlMS or the recommended rate shows
more benefit compared to the other treatments as it produced plants with high yield, lesser
. Tuber production of Potato Applied with Different Volumes of Water in La Trinidad,
Benguet | SUMALAG, DAVID I. APRIL 2013
non-marketable tubers, high percentage of survival, more vigorous, longer roots which can
be an advantage in case of water scarcity, and plants with normal time of maturity.
Recommendation
Application of 400mlEVS-800mlTBS-400mlMS per plant is suited for potato
production or 800mlEVS-800mlTBS-400mlMS (farmers practice) could be reduced during
the 1st to 30th DAE on silt loam soils.
Further evaluation is recommended to verify the results of the study under open
field.
. Tuber production of Potato Applied with Different Volumes of Water in La Trinidad,
Benguet | SUMALAG, DAVID I. APRIL 2013
LITERATURE CITED
AJAMBAR, L.D. 1989. Soil Moisture and Water on Plants. New York: McMillan
Publishing Company Inc. Pp. 3-11.
ASIAN VEGETABLE RESEARCH DEVELOPMENT CENTER (AVRDC). 1990.
Vegetable Production Training Manual. Taiwan:AVRDC. Pp. 128-130.
BAWANG, F.T. 1981. The Effect of Moisture Stress on the Growth, Yield, and Some
Postharvest Characteristic of Cultivar Cosima and red Pontiac. M.S Thesis. La
Trinidad, Benguet, Philippines. Benguet State University Pp. ix.
DEPARTMENT OF PRIMARY INDUSTRIES. 2010. Potatoes-Irrigation. Retrieved on
September
18,
2012
from
http://www.dpi.vic.gov.au/agriculture/horticulture/vegetables/potatoes/irrigation-
potatoes.
EFETHA A. 2011. Irrigation Scheduling for Potato in Southern Alberta. Retrieved on
September
2
at
http://www1.agric.gov.ab.ca/$Department/deptdocs.nsf/all/agdex13571.
ELDREDGE E.P., FLOCK R.J., JENSEN L.B., PEREIRA A.B. and C.C. SHOCK. 2006.
Drip Irrigation Guide for Potatoes in the Treasure Valley. U.S. Oregon State
University. Pp.1-8.
GABUTAN, J.D 1989. Physoilogical and Agronomic Comparison Between White Potato
and Sweet Potato in Contrasting Environments of the Philippines. La Trinidad
Benguet Philippines. Benguet State University. Pp. 29-36.
JOSE, D.C. 2008. Soil Moisture Effect on the performance of Potato (Solanumtuberosum)
Cultivars. La Trinidad, Benguet, Philippines. Benguet State University. Pp. 29-36.
KALAW, O.P. 1987. Philippine Potato Production Situation. Agro- Journal. Pp. 12-15.
KRAMER, D. J. 1993. Water Stress Physiology and Plant Growth: Agronomy Journal. Pp.
31-35.
KING, B.A. and J.C STARK. 1997. Potato Irrigation Management. University of Idaho
Cooperative Extension System. Moscow Idaho U.S. Pp. 1-4.
MUMNS S.R and C.J PEARSON. 1995. Effect of Water Deficit on Translocation of
Carbohydrates in Solanumtuberosum. Australian Journal of Plant Physiology.
Accessed at www.publish.csrio.au/?act=viewfile&fileid=pp9740529.pdf.
. Tuber production of Potato Applied with Different Volumes of Water in La Trinidad,
Benguet | SUMALAG, DAVID I. APRIL 2013
NORTHERN PHILIPPINES ROOT CROP RESEARCH AND TRAINING CENTER
(NPRCRTC). 1999. Potato Production Guide. La Trinidad, Benguet: Benguet state
University. Pp 1-2.
NORTHERN PHILIPPINES ROOT CROP RESEARCH AND TRAINING CENTER
(NPRCRTC). 1999. Potato Production Guide. La TrinnidadBenguet: Benguet State
University. Pp. 1-2.
PEREIRA, A.C and C.C SHOCK. 2006. Development of irrigation best management
practices for potato from a research perspective in the United States. Sakia.org e-
publish. Pp. 1-20.
PEREY A.C. 2012. Screening and Evaluation of Sweet Potato Genotypes for Water Stress
Resistance. La Trinidad, Benguet, Philippines. Benguet State University. Pp. ix.
ROWE, R.C AND G.A SECOR. 1993. Managing Potato Health from Emergence to
Harvest: The American Phytopathological Society. Wooster, Ohio.ASP Press
Pp.35-40.
TISDALE, S.C and W.L. NELSON. 1975. Soil Fertility and Fertilizers. New York:
McMillan Publishing Company Inc. Pp. 29-30.
UNIVERSITY OF NEBRASKA-LINCOLN, 2012. CropWatch: Potato Education Guide,
Potato Growth and Irrigation Scheduling. Retrieved on September 20, 2012 from
http://cropwatch.unl.edu/web/potato/plant_growth.
. Tuber production of Potato Applied with Different Volumes of Water in La Trinidad,
Benguet | SUMALAG, DAVID I. APRIL 2013