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Evapotranspiration relationship with pan evaporation and evapotranspiration ratio of corn under different nitrogen levels and moisture regimes
Agricultural Water Management, 3 (1980/1981) 227--231
227
Elsevier Scientific Publishing Company, Amsterdam -- Printed in The Netherlands
Short Communication EVAPOTRANSPIRATION RELATIONSHIP WITH PAN EVAPORATION AND EVAPOTRANSPIRATION RATIO OF CORN UNDER DIFFERENT NITROGEN LEVELS AND MOISTURE REGIMES
M. DEVENDER REDDY, I. KRISHNAMURTHY, IL ANAND REDDY and A. VENKATACHARI
Department of Agronomy, Andhra Pradesh Agricultural University, Hyderabad, 500 030 A.P. (India) (Accepted 10 November 1980)
ABSTRACT
Devender Reddy, M., Krishnamurthy, I.,Anand Reddy, IL and Venkatachari, A., 1981. Evapotranspiration relationship with pan evaporation and evapotranspiration ratio of corn under different nitrogen levelsand moisture regimes. Agrie. Water Manage., 3: 227--231. In a field experiment with four moisture regimes and eight nitrogen levels, the ratios between evapotranspiration and pan evaporation (Et/Eo) were low in the initial stages of crop growth and attained m a x i m u m values at 70--80% (20 and 40% available soil moisture depletion (ASMDI), 65% (60% ASMD) and 55% (80% ASMDI of the crop growth stage. Amongst nitrogen levels, the evapotranspiration ratio (ETR) was highest (3573) under no nitrogen and lowest (13121 with 180 kg N/ha. The 20% ASMD regime utilised less water (ETR = 1499) to produce a kilogram of grain than did the other moisture •regimes. The lowest evapotranspiration ratio (9141 was recorded with 20% ASMD and 180 kg N/ha in combination. The highest ETR (3954) was found with 60% ASMD and no nitrogen. An additive effect of nitrogen and moisture was found, indicating that they can be substituted one for the other, when one of them becomes a constraint.
INTRODUCTION
Evaporation from a U.S. standard open pan evaporimeter takes into acc o u n t the effects of advective energy along with other parameters of the climate; it m a y be inferred that the pan evaporimeter may serve as a good guide for scheduling irrigation. Doss et al. (1962) suggested that open pan evaporation m a y be used to estimate evapotranspiration and irrigation requirements of corn, provided a relationship between evapotranspiration and open pan evaporation has been established for a given area. Denmead and Shaw (1962) found that ratios between evapotranspiration and pan evaporation were highest during the silking to early ear development stage. The ratio of evapotranspiration b y corn to pan evaporation varied from 0.38 at emergence to 1.12 during early dough stage, then declined to 0.95 at grain matu0378-3774/81/0000--0000/$02.50 © 1981 Elsevier Scientific Publishing Company
228
rity (Doss et al., 1962). Kelly (1954) reported that in soils of low fertility, 692 kg of water was required to produce 1 kg of dry ears when manure was added, whereas 2136 kg of water was required under no manure. Aranda (1973} showed that irrigating the crop at 50% depletion gave the best grain yield and water use. For production of 1 kg grain, 530 kg of water was used. The results of 2 years' experimentation on the relationship of evapotranspiration to pan evaporation during the crop growing season under different moisture regimes and nitrogen levels, along with the evapotranspiration ratio, are reported here. MATERIALS AND METHODS
The experiment was conducted during the winter seasons (rain-free period) of 1974--75 and 1975--76 at the Agricultural College Farm, A.P. Agricultural University, Hyderabad, India. The soft of the experimental site was a sandy loam (chalka) with 0.49% organic carbon, 41 kg/ha of available e : o s , 590 kg/ha of available K20 and a pH value of 8.3. The experiment was laid out in a split plot design with eight nitrogen levels (0, 30, 60, 90, 120, 150, 180 and 210 kg N/ha) as main plot treatments and four moisture regimes (irrigation at 20, 40, 60 and 80% of available soil moisture depletion, ASMD) as sub-plot treatments replicated thrice. A basal dose of 60 kg P2Os/ha as single superphosphate, 30 kg K20/ha as muriate of potash and 30 kg/ha of zinc sulphate was applied. Nitrogen was applied in the form of urea as per the treatments in three splits viz; half as basal, and one quarter at 40 and 60 days after sowing. The cultivars under test were DHM-1 (1974--75) and DHM-101 {1975--76). The seeding was done 30 cm apart in 60-cm rows. The single value constants were: field capacity 15.17%, wilting coefficient 6.07%, and bulk density 1.56 g/cm 3, and the available soil moisture was 84 mm in a 60 cm deep soil profile. The soil moisture content between irrigations was determined b y a thermogravimetric method, drawing soil samples from 0--15, 15--30 and 30--60 cm before and after irrigation (hard murram was found b e y o n d 60 cm depth). There was no precipitation or ground water contribution during the crop growth period. Evapotranspiration per day was calculated as: Et/day =
Consumptive use during the given sampling interval Interval between the sampling in days
The daily evaporation (Eo) from standard U.S.W.B. class I open pan evaporimeter was recorded and average daffy Et/Eo ratios were calculated under the different moisture regimes. Best fit curves {third degree polynomial) for the mean Et/Eo data under different moisture regimes were determined and are presented in Fig. 1. The evapotranspiration ratio (ETR)
229
was calculated as: Seasonal consumptive use of water converted to kg/ha
ETR =
Grain yield in kg/ha
The main ETR values for 2 years are presented in Fig. 2. RESULTS AND DISCUSSION
Et/Eo ratio. There was a progressive increase in the Et/Eo ratio with the advancement of crop growth. The maximum Et/Eo ratio was observed at 70% (0.92) and 65% (0.77) of the crop growth stage in the 20% and 40% ASMD regimes respectively, whereas the m a x i m u m Et/Eo ratio of 0.70 and 0.64 was recorded at 55% of the crop growth stage in the 60% and 80% ASMD regimes respectively. This indicates that the moisture under the latter t w o regimes was n o t sufficient to meet the needs of the crop and climatic complex. Evapotranspiration ratio. The comparison of different nitrogen levels at a given moisture regime as well as different moisture regimes at a given nitrogen level indicated that the ETR decreased with increased availability of moisture and nitrogen with the exception o f increased ETR b e y o n d 180 kg N/ha. At a given moisture regime the ETR decreased from 27 to 72% with increased application of nitrogen. Better management o f soil moisture could decrease the E T R at a given nitrogen level by 11 to 57%. The mean ETR was 1312 with 180 kg N/ha, which was the lowest and indicates that the ETR will be low at o p t i m u m fertilization level. Thus the 180 kg N/ha seems to be optimum with a combination of irrigation at 40% ASMD (981) as the ETR was decreased by ~.17%, although there was a further reduction of a b o u t 16% in the ETR (i.e. 233%) at 20% ASMD (914), which was n o t commensurate with in20°/o - - e - ° 40°/o - - x - - 60°/o •- o . - - . 8 0 ° / o
ASMD ASMD ASMD ASMD
1.C
A
A
.9 0 e
z~
A
07 m°
•
O.E
,~/.
o.~
o~ ~'. ~,~ ~
o//A °
O.Z 0.-
0
i
,
i
10
20
30
× o I
40
Growing
~
,
i
50
60
70
i
80
ox /
90
i
100
season, %
Fig. I. Variation in Et/Eo ratio at different stages of crop growth as influenced by moisture regimes.
230 47 a5 43 4! 39
S
~ 37
~ 35
} 33 29 ×
27
o ~
25
g 23 ~ 2~ c
19
La
15
g 1;7 3 I 1t
9
i i - -
Fig. 2. Evapotranspiration ratio as influenced by different levels of nitrogen and moisture regimes.
creased application of water. Hence it can be concluded that the combination of about 180 kg N/ha with irrigation at 40% ASMD may be optimum for better utilisation of water. These results are in conformity with those of Anand Reddy et al. (1978). To produce 1 kg of grain, 3573 kg of water was required with no nitrogen, whereas only 1312 kg of water was required with 180 kg N/ha. This means that at optimum fertilization the productive efficiency of water increased by about 272% compared to no nitrogen. Kelly (1954) recorded an increased productive efficiency of water (309%) when manure was added. Venkatachari et al. (1976) also reported that nitrogen application and better management of soil moisture resulted, respectively, in yield increases of about 245% and 310% in corn. The lowest ETR (1499) was recorded under the 20% ASMD regime followed by the 40% (1746), 60% {2140) and 80% {2726) ASMD regimes. The highest ETR (3954) was recorded under 60% ASMD regime with no nitrogen and the lowest ETR of 914 was under 20% ASMD regime with 180 kg N/ha. This can be ascribed to
231 the higher water use efficiency under 20% ASMD regime with 180 kg N/ha (Devender R e d d y et al., 1980) Further perusal of the data reveals an additive effect of nitrogen and moisture, indicating that they can be substituted one for the other when one of them becomes a constraint. Under moisture constraint conditions, the E T R can be reduced from 27 to 46% by increased application of nitrogen even with the 80% ASMD regime. On the other hand, when the nitrogen availability is limited, the ETR can be reduced b y 11 to 41% even with the 40% ASMD regime, and can be further reduced (27 to 47%) with the 20% ASMD regime at no nitrogen and 60 kg N/ha respectively. Even under no nitrogen conditions, the 20% ASMD regime can substitute to the extent of 60 kg N/ha. Similarly, when the moisture becomes a constraint (80% ASMD), 180 kg N/ha can substitute for the 60% ASMD regime.
REFERENCES Anand Reddy, K., Bhaskar Reddy, B., Balaswamy, K. and Venkatachari, A., 1978. Effect of soil moisture and organic mulches on corn planted in different patterns. Exp. Agric., 14: 389--394. Aranda, J.H., 1973. Results from the three year experiments on the effect of irrigation regime on the yield of corn in South-West Spain. In: A. Hadas, D. Swartzendruber, P.E. Rijtema, M. Fuchs and B. Yaron (Editors), Ecological Studies--IV. Physical Aspects of Soil Water and Salts in Ecosystems. Springer Verlag, Berlin, pp. 325--330. Denmead, C.T. and Shaw, R.H., 1962. Evapotranspiration in relation to the development of the corn crop. Agron. J., 54: 505--510. Devender Reddy, M., Krishnamurthy, I., Anand Reddy, K. and Venkatachari, A., 1980. Consumptive use and daily evapotranspiration of corn under different levels of nitrogen and moisture regimes. Plant Soil, 56: 143--147. Doss, B.D., Bennet, O.L. and Aahley, D.A., 1962. Evapotranspiration by irrigated corn.
Agron. J., 54: 497--498. Kelly, O.J., 1954. Requirement and availability of soil water. Adv. Agron., 6: 67--94. Venkatachari, A., Khursheed Ahmed, M., Krishnamurthy, I., Balaiah, B. and Srinivasulu Gupta, G., 1976. Yield response of maize, sorghum and pearl millet crops to different levels of nitrogen under varying moisture regimes. Fertilizer News, 21 (9): 49--51.
227
Elsevier Scientific Publishing Company, Amsterdam -- Printed in The Netherlands
Short Communication EVAPOTRANSPIRATION RELATIONSHIP WITH PAN EVAPORATION AND EVAPOTRANSPIRATION RATIO OF CORN UNDER DIFFERENT NITROGEN LEVELS AND MOISTURE REGIMES
M. DEVENDER REDDY, I. KRISHNAMURTHY, IL ANAND REDDY and A. VENKATACHARI
Department of Agronomy, Andhra Pradesh Agricultural University, Hyderabad, 500 030 A.P. (India) (Accepted 10 November 1980)
ABSTRACT
Devender Reddy, M., Krishnamurthy, I.,Anand Reddy, IL and Venkatachari, A., 1981. Evapotranspiration relationship with pan evaporation and evapotranspiration ratio of corn under different nitrogen levelsand moisture regimes. Agrie. Water Manage., 3: 227--231. In a field experiment with four moisture regimes and eight nitrogen levels, the ratios between evapotranspiration and pan evaporation (Et/Eo) were low in the initial stages of crop growth and attained m a x i m u m values at 70--80% (20 and 40% available soil moisture depletion (ASMDI), 65% (60% ASMD) and 55% (80% ASMDI of the crop growth stage. Amongst nitrogen levels, the evapotranspiration ratio (ETR) was highest (3573) under no nitrogen and lowest (13121 with 180 kg N/ha. The 20% ASMD regime utilised less water (ETR = 1499) to produce a kilogram of grain than did the other moisture •regimes. The lowest evapotranspiration ratio (9141 was recorded with 20% ASMD and 180 kg N/ha in combination. The highest ETR (3954) was found with 60% ASMD and no nitrogen. An additive effect of nitrogen and moisture was found, indicating that they can be substituted one for the other, when one of them becomes a constraint.
INTRODUCTION
Evaporation from a U.S. standard open pan evaporimeter takes into acc o u n t the effects of advective energy along with other parameters of the climate; it m a y be inferred that the pan evaporimeter may serve as a good guide for scheduling irrigation. Doss et al. (1962) suggested that open pan evaporation m a y be used to estimate evapotranspiration and irrigation requirements of corn, provided a relationship between evapotranspiration and open pan evaporation has been established for a given area. Denmead and Shaw (1962) found that ratios between evapotranspiration and pan evaporation were highest during the silking to early ear development stage. The ratio of evapotranspiration b y corn to pan evaporation varied from 0.38 at emergence to 1.12 during early dough stage, then declined to 0.95 at grain matu0378-3774/81/0000--0000/$02.50 © 1981 Elsevier Scientific Publishing Company
228
rity (Doss et al., 1962). Kelly (1954) reported that in soils of low fertility, 692 kg of water was required to produce 1 kg of dry ears when manure was added, whereas 2136 kg of water was required under no manure. Aranda (1973} showed that irrigating the crop at 50% depletion gave the best grain yield and water use. For production of 1 kg grain, 530 kg of water was used. The results of 2 years' experimentation on the relationship of evapotranspiration to pan evaporation during the crop growing season under different moisture regimes and nitrogen levels, along with the evapotranspiration ratio, are reported here. MATERIALS AND METHODS
The experiment was conducted during the winter seasons (rain-free period) of 1974--75 and 1975--76 at the Agricultural College Farm, A.P. Agricultural University, Hyderabad, India. The soft of the experimental site was a sandy loam (chalka) with 0.49% organic carbon, 41 kg/ha of available e : o s , 590 kg/ha of available K20 and a pH value of 8.3. The experiment was laid out in a split plot design with eight nitrogen levels (0, 30, 60, 90, 120, 150, 180 and 210 kg N/ha) as main plot treatments and four moisture regimes (irrigation at 20, 40, 60 and 80% of available soil moisture depletion, ASMD) as sub-plot treatments replicated thrice. A basal dose of 60 kg P2Os/ha as single superphosphate, 30 kg K20/ha as muriate of potash and 30 kg/ha of zinc sulphate was applied. Nitrogen was applied in the form of urea as per the treatments in three splits viz; half as basal, and one quarter at 40 and 60 days after sowing. The cultivars under test were DHM-1 (1974--75) and DHM-101 {1975--76). The seeding was done 30 cm apart in 60-cm rows. The single value constants were: field capacity 15.17%, wilting coefficient 6.07%, and bulk density 1.56 g/cm 3, and the available soil moisture was 84 mm in a 60 cm deep soil profile. The soil moisture content between irrigations was determined b y a thermogravimetric method, drawing soil samples from 0--15, 15--30 and 30--60 cm before and after irrigation (hard murram was found b e y o n d 60 cm depth). There was no precipitation or ground water contribution during the crop growth period. Evapotranspiration per day was calculated as: Et/day =
Consumptive use during the given sampling interval Interval between the sampling in days
The daily evaporation (Eo) from standard U.S.W.B. class I open pan evaporimeter was recorded and average daffy Et/Eo ratios were calculated under the different moisture regimes. Best fit curves {third degree polynomial) for the mean Et/Eo data under different moisture regimes were determined and are presented in Fig. 1. The evapotranspiration ratio (ETR)
229
was calculated as: Seasonal consumptive use of water converted to kg/ha
ETR =
Grain yield in kg/ha
The main ETR values for 2 years are presented in Fig. 2. RESULTS AND DISCUSSION
Et/Eo ratio. There was a progressive increase in the Et/Eo ratio with the advancement of crop growth. The maximum Et/Eo ratio was observed at 70% (0.92) and 65% (0.77) of the crop growth stage in the 20% and 40% ASMD regimes respectively, whereas the m a x i m u m Et/Eo ratio of 0.70 and 0.64 was recorded at 55% of the crop growth stage in the 60% and 80% ASMD regimes respectively. This indicates that the moisture under the latter t w o regimes was n o t sufficient to meet the needs of the crop and climatic complex. Evapotranspiration ratio. The comparison of different nitrogen levels at a given moisture regime as well as different moisture regimes at a given nitrogen level indicated that the ETR decreased with increased availability of moisture and nitrogen with the exception o f increased ETR b e y o n d 180 kg N/ha. At a given moisture regime the ETR decreased from 27 to 72% with increased application of nitrogen. Better management o f soil moisture could decrease the E T R at a given nitrogen level by 11 to 57%. The mean ETR was 1312 with 180 kg N/ha, which was the lowest and indicates that the ETR will be low at o p t i m u m fertilization level. Thus the 180 kg N/ha seems to be optimum with a combination of irrigation at 40% ASMD (981) as the ETR was decreased by ~.17%, although there was a further reduction of a b o u t 16% in the ETR (i.e. 233%) at 20% ASMD (914), which was n o t commensurate with in20°/o - - e - ° 40°/o - - x - - 60°/o •- o . - - . 8 0 ° / o
ASMD ASMD ASMD ASMD
1.C
A
A
.9 0 e
z~
A
07 m°
•
O.E
,~/.
o.~
o~ ~'. ~,~ ~
o//A °
O.Z 0.-
0
i
,
i
10
20
30
× o I
40
Growing
~
,
i
50
60
70
i
80
ox /
90
i
100
season, %
Fig. I. Variation in Et/Eo ratio at different stages of crop growth as influenced by moisture regimes.
230 47 a5 43 4! 39
S
~ 37
~ 35
} 33 29 ×
27
o ~
25
g 23 ~ 2~ c
19
La
15
g 1;7 3 I 1t
9
i i - -
Fig. 2. Evapotranspiration ratio as influenced by different levels of nitrogen and moisture regimes.
creased application of water. Hence it can be concluded that the combination of about 180 kg N/ha with irrigation at 40% ASMD may be optimum for better utilisation of water. These results are in conformity with those of Anand Reddy et al. (1978). To produce 1 kg of grain, 3573 kg of water was required with no nitrogen, whereas only 1312 kg of water was required with 180 kg N/ha. This means that at optimum fertilization the productive efficiency of water increased by about 272% compared to no nitrogen. Kelly (1954) recorded an increased productive efficiency of water (309%) when manure was added. Venkatachari et al. (1976) also reported that nitrogen application and better management of soil moisture resulted, respectively, in yield increases of about 245% and 310% in corn. The lowest ETR (1499) was recorded under the 20% ASMD regime followed by the 40% (1746), 60% {2140) and 80% {2726) ASMD regimes. The highest ETR (3954) was recorded under 60% ASMD regime with no nitrogen and the lowest ETR of 914 was under 20% ASMD regime with 180 kg N/ha. This can be ascribed to
231 the higher water use efficiency under 20% ASMD regime with 180 kg N/ha (Devender R e d d y et al., 1980) Further perusal of the data reveals an additive effect of nitrogen and moisture, indicating that they can be substituted one for the other when one of them becomes a constraint. Under moisture constraint conditions, the E T R can be reduced from 27 to 46% by increased application of nitrogen even with the 80% ASMD regime. On the other hand, when the nitrogen availability is limited, the ETR can be reduced b y 11 to 41% even with the 40% ASMD regime, and can be further reduced (27 to 47%) with the 20% ASMD regime at no nitrogen and 60 kg N/ha respectively. Even under no nitrogen conditions, the 20% ASMD regime can substitute to the extent of 60 kg N/ha. Similarly, when the moisture becomes a constraint (80% ASMD), 180 kg N/ha can substitute for the 60% ASMD regime.
REFERENCES Anand Reddy, K., Bhaskar Reddy, B., Balaswamy, K. and Venkatachari, A., 1978. Effect of soil moisture and organic mulches on corn planted in different patterns. Exp. Agric., 14: 389--394. Aranda, J.H., 1973. Results from the three year experiments on the effect of irrigation regime on the yield of corn in South-West Spain. In: A. Hadas, D. Swartzendruber, P.E. Rijtema, M. Fuchs and B. Yaron (Editors), Ecological Studies--IV. Physical Aspects of Soil Water and Salts in Ecosystems. Springer Verlag, Berlin, pp. 325--330. Denmead, C.T. and Shaw, R.H., 1962. Evapotranspiration in relation to the development of the corn crop. Agron. J., 54: 505--510. Devender Reddy, M., Krishnamurthy, I., Anand Reddy, K. and Venkatachari, A., 1980. Consumptive use and daily evapotranspiration of corn under different levels of nitrogen and moisture regimes. Plant Soil, 56: 143--147. Doss, B.D., Bennet, O.L. and Aahley, D.A., 1962. Evapotranspiration by irrigated corn.
Agron. J., 54: 497--498. Kelly, O.J., 1954. Requirement and availability of soil water. Adv. Agron., 6: 67--94. Venkatachari, A., Khursheed Ahmed, M., Krishnamurthy, I., Balaiah, B. and Srinivasulu Gupta, G., 1976. Yield response of maize, sorghum and pearl millet crops to different levels of nitrogen under varying moisture regimes. Fertilizer News, 21 (9): 49--51.