Macromanagement of deficit-irrigated peanut with sprinkler irrigation

Precision irrigation management and scheduling, as well as developing site- and cultivar-specific crop coefficient (Kc), and yield response factor to water deficit (ky) are very important parameters for efficient use of limited water resources. This study investigated the effect of deficit irrigation, applied at different growth stages of peanut with sprinkler irrigation in sandy soil, on field peanut evapotranspiration (ETc), yield and yield components, and water use efficiencies (IWUE and WUE). Also, yield response factor to water deficit (ky), and site- and cultivar-specific Kc were developed. Four treatments were imposed to deficit irrigation during late vegetative and early flowering, late flowering and early pegging, pegging, and pod formation growth stages of peanut, and compared with full irrigation in the course of the season (control). A soil water balance equation was used to estimate crop evapotranspiration (ETc). The results revealed that maximum seasonal ETc was 488mm recorded with full irrigation treatment. The maximum value of Kc (0.96) occurred at the fifth week after sowing, this value was less than the generic values listed in FAO-33 and -56 (1.03 and 1.15), respectively. Dry kernels yield among treatments differed by 41.4%. Deficit irrigation significantly affected yields, where kernels yield decreased by 28, 39, 36, and 41% in deficit-irrigated late vegetative and early flowering, late flowering and early pegging, pegging, and pod formation growth stages, respectively, compared with full irrigation treatment. Peanut yields increased linearly with seasonal ETc (R2=0.94) and ETc/ETp (R2=0.92) (ETp=ETc with no water stress). The yield response factor (ky), which indicates the relative reduction in yield to relative reduction in ETc, averaged 2.9, was higher than the 0.7 value reported by Doorenbos and Kassam [Doorenbos, J., Kassam, A.H., 1979. Yield response to water. FAO Irrigation and Drainage Paper 33, Rome, Italy, 193 pp.], the high ky value reflects the great sensitivity of peanut (cv. Giza 5) to water deficit. WUE values varied considerably with deficit irrigation treatments, averaging 6.1 and 4.5kgha-1mm-1 (dry-mass basis) for pods and kernels, respectively. Differences in WUE between the driest and wettest treatment were 31.3 and 31.3% for pods and kernels, respectively. Deficit irrigation treatments, however, impacted IWUE much more than WUE. Differences in IWUE between the driest and wettest treatment were 33.9 and 33.9% for pods and kernels, respectively. The results revealed that better management of available soil water in the root zone in the course of the season, as well as daily and seasonal accurate estimation of ETc can be an effective way for best irrigation scheduling and water allocation, maximizing yield, and optimizing economic return.Crop coefficient (Kc) Evapotranspiration (ET) Groundnut Water stress Water use Water use efficiency Water productivity Yield response factor (ky)

Proceedings of the 21st annual Central Plains irrigation conference, Colby Kansas, February 24-25, 2009

Presented at the the 21st annual Central Plains irrigation conference on February 24-25, 2009 in Colby, Kansas.Includes bibliographical references.Decisions about when to initiate and terminate the irrigation season are important irrigation macromanagement decisions that can potentially save water and increase net income when made correctly, but can have negative economic consequences when made incorrectly. A combination of nine years of pre-anthesis water stress studies and sixteen years of post-anthesis water stress studies for corn was conducted at the Kansas State University Northwest Research-Extension Center in Colby, Kansas on a productive, deep, silt loam soil. Overall, the pre-anthesis water stress studies suggest that corn grown on this soil type has great ability to handle early-season water stress, provided the water stress can be relieved during later stages. A critical factor in maximizing corn grain yields as affected by pre-anthesis water stress is maximizing the kernels/area. Maintaining a water deficit ratio (well-watered calculated corn water use / sum of irrigation and precipitation) greater than 0.7 to 0.8 or limiting available soil water depletion in the top 4 ft of soil profile to approximately 30% maximized the kernels/area. Overall, the post-anthesis water stress studies suggest that corn yield is nearly linearly related to the amount of crop water use during the post-anthesis period and that total crop water use amounts may average nearly 17 inches. Producers should plan for crop water use during the last 30 and 15 day periods that may average nearly 5 and 2 inches, respectively, to avoid yield reductions. Management allowable depletion during the post-anthesis period should be limited to 45% of the available soil water for an 8-ft profile on the deep silt loam soils of this climatic region