To help make decisions on shifting of crop species in water management strategies, information is needed on comparative water use characteristics of the principal row crops. The objective of this study was to compare the water use characteristics of six row crops grown in a replicated and randomized field experiment. Crops were corn (Zea mays L.), grain sorghum (Sorghum bicolor (L.) Moench), pearl millet (Pennisetum americanum (L.) Leeke), pinto bean (Phaseolus vulgaris L.), soybean (Glycine max (L.) Merr.), and sunflower (Helianthus annuus L.). Crops were grown near Manhattan, KS, on Muir silt loam (Cumulic Haplustoll) in 1981 and on Eudora silt loam (JFiuventic Hapludoll) in 1982, and near Tribune, KS, on Ulysses silt loam (Aridic Haplustoll) in both 1981 and 1982.Soil water content was determined to the 3.1-m soil profile depth by the neutron attenuation method. Measured evapotranspiration (ET) was calculated as the sum of soil water depletion, rainfall, and irrigation. Reference ET was calculated by using the original Jensen-Haise equation. The maximum value of measured ET /reference ET was greater for sunflower (1.35) than for the other five crops (ranged from 1.05 to 1.15). The mean daily water use rate of sunflower (6.1 mm d-1 ) was 22% greater than the mean of the other five crops (5.0 mm d-1 ). The mean dry matter water use efficiency was 17.5 Mg ba-• m-• for the group of C 3 crops (pinto bean, soybean, and sunflower) and 33.3 Mg ba-• m-• for the group of C 4 crops (corn, grain sorghum, and pearl millet). Sunflower depleted significantly more water from deeper soil depths (0.99-1.60 m) than the other five crops at Manhattan in 1981 and 1982. Our findings consistently showed that sunflower bad a greater daily water use rate than the other five crops.

Wheat (Triticum aestivum L.) in the central or southern Great Plains is grown in a 2‐yr wheat‐fallow (WF) cropping system or with grain sorghum [Sorghum bicolor (L.) Moench] in a 3‐yr wheat‐sorghum‐fallow (WSF) system. Tillage during fallow causes loss of crop residue and soil water. Long‐term studies were conducted at Garden City and Tribune, KS, to determine the effects of cropping system and reduced tillage on available soil water and yield of dryland winter wheat and grain sorghum. Conventional (CT), reduced (RT), minimum (MT), and no‐tillage (NT) systems were compared in WF and WSF. These treatments also were compared with CT in sorghum‐fallow (SF), continuous sorghum (SS), and continuous wheat (WW). Reductions in tillage resulted in increased available soil water and yield. Reduced tillage resulted in increased WF yields at both locations, while WSF wheat yields were increased at Tribune. Sorghum yields were more consistently increased by reduced tillage at Tribune. Sorghum‐fallow yields were higher than WSF sorghum yields at Tribune. Wheat‐fallow yields usually did not differ from WSF wheat yields at either location. Sorghum yields in WSF exceeded SS yields 67% of the time at Garden City. At Tribune, WSF‐RT yields exceeded SS yields 73% of the time, while WSF‐CT yields were no better or less than SS yields 60% of the time. Continuous wheat yields were less than other wheat yields 98% of the time. In terms of soil water storage and yield, the WSF system is appropriate for both locations, and is more effective when combined with reduced tillage, particularly at Tribune.

No abstract

Research results are lacking that compare the yield benefit from a limited amount of irrigation water applied off-season vs. in-season. Also lacking is a partitioning of field water losses during winter into the profile drainage and evaporation components. The objectives of this work were: (i) to examine grain yield and water use of corn (Zea mays L.) and winter what (Triticum aestivum L.) in irrigation schemes that use fall vs. spring irrigations; and (ii) to partition field water loss during winter into the profile drainage and evaporation components. The field work was done near Tribune, KS, on a Ulysses silt loam soil (fine-silty, mixed, mesic Aridic Haplustoll). Timing of the off-season irrigation (fall vs. spring) did not influence corn grain yield. In irrigation schemes identical except that off-season irrigation was or was not applied, off-season irrigation did not influence corn grain yield significantly. Maximum grain yield benefit in corn from irrigation was achieved when water was applied in-season. In winter wheat receiving only one irrigation, fall irrigated wheat yielded 20SS kg ha-• more grain (3-yr mean) than wheat irrigated only in spring. Among the irrigation schemes containing fall irrigation, there was no significant difference in winter wheat grain yield, even though the total irrigation amount ranged from 1S2 to 4S6 mm. Drainage losses during winter were less than S% as much as evaporation losses at mean profile water contents during winter of less than SO% available soil water. At greater than SO% available soil water, the relative contribution of drainage in profile water loss increased with increasing profile water content. Drainage losses equalled evaporation losses at a mean profile water content during winter of O.S7 m (80% available soil water). Off-season irrigation of corn was not a water efficient practice. Fall irrigation of winter wheat was a water efficient practice that allowed continuous cropping in a region where some rotation that includes fallow is the dryland altern!_ltive.

Maximum yield production in monocultural cropping systems requires annual applications of fertilizer to maintain adequate soil nutrient levels. The rates of applied N and P fertilizers may vary from conservative to excessive applications. Experiments were established at two locations (Ardic Haplustoll and Aridic Argiustoll) to evaluate the effects of annual applications of N and P, over a period of several years, on corn (Zea mays L.) grain yields and the accumulation of these nutrients in the soil. Maximum grain yields were consistently maintained with N applications of 134 to 180 kg/ha and P applications of 20 kg/ha. Applications of N‐rates higher than the optimum resulted in accumulations of residual NO3‐N and subsequent leaching. At one location the soil P level was maintained constant for 21 years with the 20‐kg P rate. A similar trend was observed for the initial 10 years of the second experiment, however, for the last 4 years soil‐P has increased at the rate of 4 ppm annually.