Apparent Water Use Efficiency Research Articles

Short-duration mungbean (Vigna radiata (L.) R. Wilczek) genotypes differ in performance, water use and apparent water-use efficiency in southern Lao PDR

Improving nutrition-sensitive food security is important in low-income, food-deficit nations like Lao PDR, where subsistence farmers rely on a single rainfed lowland rice crop in the wet season. Access to resource conservation technologies, small on-farm water storages and electricity are starting to allow farmers to consider post-rice crops. With water availability still limited, short-duration pulse crops may be viable. This paper examined grain yield and water use during grain filling of eight short-duration mungbean genotypes after rainfed lowland rice at Champhone and Pakse in southern Lao PDR in the 2013 dry season. Two supplementary watering regimes were used, watered every 15 days (at 15, 30 and 45 days), and watered as needed at the first sign of visible wilting (at 23 and 45 days), with three replicates. Soil volumetric water content was measured by time-domain reflectometer. Over two drying cycles, VC1913A, VC3890A and VC7118A used significantly less water than other genotypes at both sites. Genotypes VC7118A and NM94 were higher yielding at Champhone, and VC6310 was higher yielding at Pakse. The relationship between grain yield and water use during grain filling was less straight forward, as it applied within apparent water-use efficiency categories. Overall, VC7118A was superior, due to its effective combination of higher apparent water-use efficiency during grain filling, lower water use in grain filling, and higher grain yield. NM94 also performed well, but required more water for similar yield performance. Drill sowing would allow timely establishment of the post-rice crop to utilize residual soil water in the dry season. These results suggest that mungbeans have a role as a post-rice crop with supplementary irrigation in Lao PDR and comparable environments, to improve nutrition-sensitive food security.

Yield Response of Corn to Irrigation on Sandy Soils1

AbstractIrrigation is being developed on large areas of coarse and moderately coarse‐textured soils in North Dakota. Extensive areas of similar soils, including those in adjacent States, are near areas planned for irrigation. Knowledge of crop response to water is needed to effectively use irrigation in these large areas. The objective of this study was to investigate the effects of irrigation and precipitation, and to use the Mitscherlich equation to evaluate the effect of limited water supply on crop yields and apparent water use efficiencies. Yield response of corn (Zea mays L.) to the amount of water received (irrigation and precipitation) was investigated in this 3‐year field study. The corn was grown on a Hecla loamy fine sand, a Udic Haploboral, and irrigated weekly at rates based on predicted evapotranspiration calculated using the Jensen‐Haise equation. Irrigation with more water than the amount predicted by the Jensen‐Haise equation did not significantly increase forage or grain yield for any single year, but did significantly increase average grain production over the 3‐year period. Successive, larger increments in the amount of water applied to the crop resulted in successively smaller increases in forage and grain yields. Mitscherlich equations fitted yield data for all 3‐years and predicted limiting yields of 16.48 metric tons/ha of oven‐dry forage and 10,150 kg/ha of grain at 15% moisture. For oven‐dry forage production, apparent water‐use efficiency (AWUE) was about 0.28 and 0.21 metric ton/ha‐cm of water applied (precipitation plus irrigation) between emergence and final harvest for the nonirrigated and highest irrigation rate treatments, respectively. For the corresponding treatments, the respective AWUE's for corn grain production were 323 and 167 kg/ha‐cm of water received (between 3 weeks before silking and final harvest). Yield response to irrigation treatments that considered precipitation probability at Oakes, North Dakota, were calculated. Results indicated that in 95% of the cropping seasons at least 8.9, 10.9, 12.4, or 13.4 metric ton/ha of oven‐dry forage and 6,070, 7,230, 8,060, or 8,650 kg/ha of corn grain at 15% moisture could be expected from irrigating with 20, 30, 40, or 50 cm of water, respectively. In 50% of the cropping seasons, however, only 6.3 metric ton/ha of forage and 3,770 kg/ha of grain or less could be expected with no irrigation.