Seasonal Water Requirement Research Articles

Water balance and maize yield following improved sesbania fallow in eastern Zambia

Sesbania [Sesbania sesban (L.) Merr.] fallows are being promoted as a means for replenishing soil fertility in N-depleted soils of small-scale, resource-poor farmers in southern Africa. Knowledge of soil water distribution in the soil profile and water balance under proposed systems is important for knowing the long-term implications of the systems at plot, field and watershed levels. Soil water balance was quantified for maize (Zea mays L.) following 2-year sesbania fallow and in continuous maize with and without fertilizer during 1998–1999 and 1999–2000 at Chipata in eastern Zambia. Sesbania fallow increased grain yield and dry matter production of subsequent maize per unit amount of water used. Average maize grain yields following sesbania fallow, and in continuous maize with and without fertilizer were 3, 6 and 1 Mg ha−1 with corresponding water use efficiencies of 4.3, 8.8 and 1.7 kg mm−1 ha−1, respectively. Sesbania fallow increased the soil-water storage in the soil profile and drainage below the maximum crop root zone compared with the conventionally tilled non-fertilized maize. However, sesbania fallow did not significantly affect the seasonal crop water use, mainly because rainfall during both the years of the study was above the normal seasonal water requirements of maize (400 to 600 mm). Besides improving grain yields of maize in rotation, sesbania fallows have the potential to recharge the subsoil water through increased subsurface drainage and increase nitrate leaching below the crop root zone in excess rainfall seasons.

EVAPOTRANSPIRATION OF LONG-DAY ONION, IRRIGATED BYMICROSPRINKLERS

Investigations were made on the seasonal water requirements of annual onion cv. Santana grown under optimal schedule of irrigation and water stress. Three variants with different irrigation rates (1.00 IR, 0.75 IR and 0.50 IR) were studied. A system for microsprinkler irrigation was used, the time of irrigation being determined by estimating soil moisture. The first irrigation was done after sowing and the last - at the lodging of onion leaves. The actual evapotranspiration for the three irrigated variants was established. Its total value in the optimal variant over the irrigation season was 337,84 mm. The evapotranspiration productivity varied in the range of 8,58 - 14,55 kg/mm. The „relative yield - relative evapotranspiration” relationship was determined.

Effect of drip irrigation on yield of cabbage ( Brassica oleracea L. var. capitata) under mulch and non-mulch conditions

The experiments were conducted on the lateritic sandy loam soils of Kharagpur, West Bengal, India during middle of September–January for 3 years (1997–2000) to evaluate the economic feasibility of growing cabbage crop under drip irrigation with mulches. Actual evapotranspiration for cabbage crop was estimated by using the modified Penman method and net daily irrigation requirement was estimated after subtracting effective rainfall. Estimated irrigation requirement was supplied by a 4 l h −1 emitter for four plants with the drip irrigation system being operated from 70 to 101 min per day during the crop season. The average seasonal water requirement of crop was estimated to be 400 mm. The yields of the cabbage under 25 μm thick black plastic mulch (PM) were studied using three levels of drip irrigation which applied 100% (VD), 80% (0.8VD) and 60% (0.6VD) of the estimated irrigation requirement. The yield response under two organic mulches, rice husk with drip (VDH) and paddy straw with drip (VDS) were also studied. For comparison, furrow irrigated (VF) treatments were used and the study revealed 62.44% higher yield in case of drip (VD) as compared to furrow irrigation. Even higher yields were obtained for drip irrigation with PM (VD+PM), 111.72 t ha −1 as compared to 106.68 t ha −1 for (VD). The treatments VDH and VDS showed, respectively, 2.05 and 1.18% higher yield when compared with drip (VD) alone. The net seasonal income was estimated to be highest as US$ 4333 in case of treatment VD+PM. The highest benefit–cost ratio of 8.17 was obtained for furrow irrigation (VF) followed by 6.99 for drip (VD). The net profit per mm of water used was obtained to be highest (US$ 16.51) in case of drip irrigation (0.6VD) followed by US$ 16.32 under the treatment 0.6VD+PM. The highest yield per unit quantity of water used was 427.04 kg ha −1 mm −1 for the treatment 0.6VD+PM. The study reveals that drip irrigation has a definite role in increasing the productivity of cabbage.

Deficit irrigation strategies using midday stem water potential in prune

The effects of two levels of water stress on fruit yield, quality and relative economic return were investigated in French prune over a 3-year period. Water stress was achieved by allowing a progressive decrease in midday stem water potential (midday Ψstem) over the season. The control treatment (T1) received approximately 100% of the estimated seasonal crop water requirements, but did exhibit a decline in midday Ψstem during the season to below that expected for fully irrigated prune trees (–1.0 MPa). For the moderate and severe stress treatments (T2 and T3 respectively), irrigation was managed to reach a target midday Ψstem of approximately –1.5 and –2.0 MPa, respectively, by harvest. Treatments T2 and T3 received an average of 57% and 38% of estimated seasonal crop water requirements, respectively, over the 3 years of the study but this did not negatively impact fruit dry mass accumulation or fruit quality. Over a 3-year period, the stress treatments had less dry mass of fruit dropped, fewer fruit dropped, improved (lower) fruit hydration ratios, less fruit side-cracking and decreased vegetative growth compared with the control. There were no significant effects of either of the stress treatments on flowering, dry fruit yields or relative economic return for the 3-year average data. However, a significantly lower relative economic return for T3 during the third year of the study suggests that the cumulative effect of this level of stress may be detrimental to long-term prune productivity. Allowing a progressive decline in midday Ψstem to approximately –1.5 MPa by harvest appears to be an effective way to reduce irrigation and maintain economic returns in French prune.

Irrigation management for corn in the northern Great Plains, USA

Irrigation management influences production costs and affects leaching of nutrients to groundwater. This study was conducted to compare irrigation scheduling techniques on a field-scale site and to determine whether significant irrigation water savings and equivalent yields could be achieved compared with the practices of other commercial growers in the local area. The effects of four irrigation scheduling techniques on seasonal irrigation water requirements and corn grain yields were studied for the 1990–1995 seasons at a field-scale (53.4 ha) site within the Oakes Test Area (OTA) of the Garrison Diversion Unit in southeastern North Dakota, USA. The four scheduling techniques, applied with field quadrants and seasons as dimensions of a modified Latin square statistical design, included irrigating based on tensiometer and infrared canopy temperature measurements, two water balance methods, and irrigating based on CERES–Maize estimates of plant-extractable soil water. No statistically significant differences in seasonal irrigation totals were found between irrigation scheduling methods or irrigation quadrants, while statistically significant differences were found for season. Corn grain yield was significantly affected by seasons, quadrants, and irrigation scheduling methods for both the current and previous seasons. Compared to other commercial growers in the OTA, this study maintained 5% higher yields and saved approximately 30% in irrigation inputs. Careful irrigation scheduling, based on any of the four techniques, offers the potential to reduce input costs for irrigated corn production in the area.

Response of okra ( Abelmoschus esculentus (L.) Moench.) to drip irrigation under mulch and non-mulch conditions

Field experiments were conducted on the lateritic sandy loam soils of Kharagpur, West Bengal, India during spring–summer (February–May) seasons for 3 years (1995–1997) to evaluate the economic feasibility of drip irrigation in combination with different types of mulches for an okra crop. Actual evapotranspiration for okra crop was estimated using modified Penman method. The net irrigation volume ( V) was determined after deducting the effective rainfall. The net average seasonal water requirement of crop was estimated to be 665 mm. The effect of three irrigation levels viz. VD, 0.8 VD and 0.6 VD with drip in conjunction with black plastic mulch were studied on biometric and yield response. Effect of two organic mulches (rice husk and rice straw) were also studied with drip irrigation. The results of furrow irrigation either alone or in conjunction with black plastic mulch conditions were compared with drip irrigation in terms of growth and yield of the crop. The study indicated that 100% irrigation requirement met through drip irrigation along with black plastic mulch (VD+PM) gave the highest yield (14.51 t ha −1 ) with 72% increase in yield as compared to furrow irrigation. The net seasonal income, benefit–cost ratio and the yield per unit depth of water used, were found to be highest for drip irrigation with black plastic mulch (VD+PM), drip irrigation alone (VD) and drip irrigation with black plastic mulch (0.6 VD+PM), respectively.

Oscillation of potential evapotranspiration in India and its significance on seasonal potential water requirement of crops

In this study, the normal weekly potential evapotranspiration values of 47 stations situated over different parts of the country have been subject harmonic analysis, The amplitude of the stations varies greatly ranging from 5 mm in the west coast of peninsular India to 24 mm over northwest parts of the country .The peak of weekly oscillation attains its maximum value around end of February/early March over extreme southwest coast of the country , while it is third week of June over northwest Rajasthan. northeast India and over small pockets around Rajamundry of Andhra Pradesh and Pusa of Bihar. A negative correlation between latitude and the seasonal (kharif, rabi and summer) potential water need of the respective stations of different groups indicates that potential water demand of crops at different seasons in each of the groups is inversely proportional with increase in latitudinal value except for kharif season of group IV stations where it is reverse.

Irrigation water requirements of wheat in the life zones of Saudi Arabia

Weighted-mean crop coefficients of wheat in 11 life zones of Saudi Arabia were estimated according to an FAO method. Evapotranspiration rates of wheat grown in these life zones were then computed using previously estimated reference rates of evapotranspiration. Leaching requirements of water ranging in salinity from 0·5 to 6·0 dS/m were calculated for sprinkler (pivot) and surface irrigation systems. Gross seasonal irrigation water requirements of wheat grown under both irrigation systems in these life zones were estimated for waters varying in salinity.

Irrigation requirements of rice under shallow water table conditions

Irrigation experiments with wetland rice ( Oryza sativa L.) paddies for 2 years under shallow water table conditions showed that intermittent submergence 3 days after water vanished from the surface of the soil produced grain yields similar to continuous submergence. Whereas irrigation was necessary every 3 days in clay loam (S 1) and silty clay loam (S 2), and every 2 days in loam (S 3) under continuous submergence of 5 ± 2.5 cm, it was necessary only every 7 days in S 1 and S 2, and every 6 days in S 3, under intermittent submergence of 7.5 cm 3 days after water vanished from the soil surface. The intermittent submergence led to a 34–43% saving of irrigation water. Percolation losses were reduced by 36, 31 and 25% in S 1, S 2 and S 3, respectively, as compared to those under continuous submergence. Average percolation rate was 6.1–6.4 mm day −1 in S 1 and S 2, and 10.1 mm day −1 in S 3. Yields were higher in the better drained S 3 than in the poorly drained S 1 and S 2. Average ET ranged from 7.4 to 9.2 mm day −1 under continuous submergence and from 6.1 to 7.1 mm day −1 under intermittent submergence. The intermittent submergence produced 7.2–14.7 kg more grain per cm of ET than continuous submergence. Regression of seasonal water requirement (WR) on percolation ( P c) and ET, and grain yield on WR and ET was highly significant. Yield was better correlated with ET ( r = 0.92) than with WR ( r = 0.86).

Predicting Seasonal Irrigation Water Requirements on Coarse-Textured Soils

ABSTRACT Awater-balance model has been developed for predicting seasonal irrigation water requirements. The model treats the soil as a multi-layered water storage reservoir. Reservoir capacity is defined by soil water desorption data, rate of root growth, and effective rooting depth. Water withdrawal rate or crop water use is determined from pan evaporation data corrected to potential ET and converted by consideration of plant growth stage. Rainfall is partitioned into runoff, effective precipitation, and deep percolation. Field data from corn and soybeans during the seasons 1979-81 on two soil types were used for verification. The mean absolute difference between predicted and measured seasonal irrigation water requirements was 16%. Simulation data were fitted to frequency distributions, and irrigation requirements are expressed in terms of probabilities.

SORGHUM AND BARLEY IN SOUTHERN ALBERTA: GRAIN YIELD RESPONSE TO IRRIGATION AND FERTILIZER

The seasonal water requirements of irrigated grain sorghum, the interaction between water use and applied N fertilizer, and the comparative water use efficiences of sorghum and barley were determined in southern Alberta over a 3-yr period. Peak daily water use of 6 mm for sorghum was 1 mm lower than that determined previously for barley. Seasonal water use (500 mm) was 20% greater than for barley because of sorghum’s longer growing season. Under adequate irrigation, both sorghum and barley responded linearly to applied N up to 80 kg/ha, but when water was restricted, sorghum showed less response than barley. Water-use efficiency (kg of grain/m3 of water used) decreased for both crops with increasing water availability but maximum yields were achieved under irrigation. When sorghum was favored with a long, warm growing season, it produced as much grain (6900 kg/ha) and used water as efficiently (1.25 kg/m3) as did barley.

Irrigated Corn Yield Response to Water

ABSTRACT IRRIGATED corn yield response to water deficits, water-yield functions, and potential for limited irriga-tion were evaluated during a 3-yr level border field study at Bushland, TX (Southern High Plains). Seasonal evapotranspiration (ET) by treatments irrigated for high yields was 66.7 to 78.9 cm, seasonal irrigation water re-quirements were 40 cm, grain yields were 9,520 to 10,850 kg/ha, and seasonal water-use efficiencies were 125 to 146 kg/ha-cm. Water deficits reduced average grain yields by 172 to 287 kg/ha-cm and average seasonal water-use efficiencies by 67 to 94 percent below the ade-quate water-high yield treatment. The threshold seasonal ET for beginning of grain yield was about one-half of seasonal ET for high yields. The relationship of ET and grain yield was compared with results from other studies. Because of sensitivity of corn to plant-water stress in the climate of relatively high evaporative demand in the Southern High Plains, we concluded that limited irriga-tion of corn should not be practiced.