Dryland wheat (Triticum aestivum L.) in the Great Plains generally is planted in a wheat‐ fallow (WF) rotation. Wheat grown in rotation with a summer row crop like corn (Zea mays L.), sorghum [Sorghum bicolor (L.) Moench], or sunflower [Helianthus annuus var. macrocarpus (DC.) Ck11.] increases cropping intensity, allowing a crop to be produced annually on 67 to 100% of tillable acres. A review of economic analyses of dryland cropping systems in the Great Plains was conducted to compare net returns, production costs, financial risk, and compatibility with the 1990 Farm Bill. Seven of eight studies reported that net returns were greater from a more intensive crop rotation than from WF when reduced‐tillage (RT) or notill (NT) were used following wheat harvest and prior to the summer crop planting. With government program payments, WF was more profitable with conventional tillage (CT).than with NT. Production costs increased as cropping intensity increased and tillage decreased. Economic risk analysis showed that wheat‐sorghum‐fallow (WSF) was less risky than WF in Kansas. Cropping systems using more intensive rotations with less tillage had higher production costs than WF, but also had increased net returns and reduced financial risk, while remaining in compliance with 1990 Farm Bill provisions. Research Question Wheat‐fallow (WF) is the major dryland crop rotation in the Great Plains. More intensive crop rotations using less tillage should increase grain production per tillable acre. The objectives of this study were to examine available reports of research into various crop rotations to determine if cropping alternatives more profitable than WF exist and how alternative cropping systems affect net returns, production costs, financial risk, and government program compliance. Literature Summary Harvested acres of dryland fallow winter wheat in western Kansas, western Nebraska, and eastern Colorado averaged 6.6 million acres from 1991 to 1993 compared with less than 1.6 million acres of dryland spring and summer crops (Fig. ). The ratio of wheat acres to spring and summer crop acres has been fairly consistent during this time. Thus, WF is the major crop rotation on dryland acres in the Central Great Plains. Several studies of dryland cropping systems in the Great Plains using reduced tillage (RT) or no tillage (NT) or more intensive crop rotations were compared with WF in terms of reduced soil erosion, increased grain yield, and increased water use efficiency. Although considerable research has been conducted on the agronomics of dryland cropping systems, only a few studies have analyzed the costs and returns to these systems. 1 Harvested acres of dryland crops in western Kansas, western Nebraska, and eastern Colorado. Applied Questions Are there cropping systems more profitable than WF for dryland producers in the Great Plains? Crop rotations producing a crop on 67 to 75% of tillable acres on an annual basis using RT or NT were found to be more profitable than WF in the Central and Southern Great Plains. Continuous...

The dryland winter wheat (Triticum aestivum L.)‐grain sorghum [Sorghum bicolor (L.) Moench]‐fallow rotation is suitable for large areas of the U.S. Great Plains. High temperatures and potential evapotranspiration limit the number of other crops that can be grown. Sunflower (Helianthus annuus L.) is drought tolerant, but crops such as corn (Zea mays L.) and soybean [Glycine max (L.) Merr.] are perceived to lack sufficient heat and drought tolerance for semiarid areas. A study was conducted near Garden City, KS, from 1991 through 1995 to compare yield and water uses of conventional tillage (CT) and no tillage (NT) corn, grain sorghum, sunflower, and soybean to determine if crops other than grain sorghum are suitable for dryland production. Conventional tillage (CT) and no tillage (NT) were included in a wheat‐row crop‐fallow rotation. Corn and soybean were similar in their depletion of soil water, as were sorghum and sunflower. Below a depth of 1.2 m, sorghum and sunflower removed the most water. Sunflower removed the most water from the last 0.3 m of the profile and probably removed deeper water. Sorghum and sunflower removed an average of 19 mm more water from the 1.8‐m soil profile than did corn and soybean. No‐till increased yields of corn in 3 yr, of sorghum and sunflower in 2 yr, and of soybean in 1 yr. Corn had the greatest yield response to NT, averaging 31%. Average yields of corn were 25% higher than sorghum yields, whereas average yields of sunflower were 83% higher than soybean yields. Other crops can be successfully grown in the wheat‐row crop‐fallow rotation, but sorghum should occupy the most acres until the other crops have been tested under different climatic conditions.

Corn (Zea mays L.) is grown on more irrigated hectares than any crop in the Great Plains. Much of this area is irrigated from the Ogallala aquifer, which is being depleted in some areas, particularly in the central and southern portions of the region. Research was conducted at Garden City, KS, from 1994 through 1997 to evaluate the effects of various combinations of irrigation, N rate, and plant population on water use and yield of corn and to determine if limited irrigation is a viable alternative to returning irrigated hectares to dryland in an area of declining groundwater. Treatments were zero, one, two, and three irrigations, each consisting of 150 mm of water, applied to corn grown with conventional tillage (CT) and no tillage (NT). Appropriate N rates and plant populations were used with each irrigation treatment to give the management systems S0, S1, S2, and S3. The single irrigation was at tassel (VT) and the two irrigation treatment was at VT and at the dough stage of grain fill (R4). Corn irrigated three times received a vegetative irrigation at the 9 to 10 leaf stage (V9) plus irrigations at VT and R4. Management system S1 increased yield by an average of 1.76 Mg ha−1 or 29%. On average S2 and S3 increased yields an additional 11 and 13%, respectively. No till increased yield and water‐use efficiency (WUE) in 2 of 4 yr. On average NT increased yield by 0.56 Mg ha−1, and WUE by 0.96 kg ha−1 mm−1 . Conclusions are that corn will produce adequate yields with one or more irrigations; thus, limited irrigation combined with proper fertility and plant population is a viable alternative to dryland in an area of declining groundwater.

Yields of dryland crops are limited by precipitation in the Great Plains. Winter wheat (Triticum aestivum L.) grown in the wheat‐fallow (WF) system (one crop in 2 yr) occupies the greatest area. The use of grain sorghum [Sorghum bicolor (L.) Moench] in the wheat‐sorghum‐fallow (WSF) system (two crops in 3 yr) is becoming popular. Other cropping systems include sorghum‐fallow (SF) and continuous sorghum (SS). Research was conducted in the central Great Plains at Garden City, KS, from 1987 through 1992 to quantify soil water storage and use and grain yield in the WF, WSF, SS, and SF systems in order to develop more efficient dryland grain production systems. No tillage (NT) and conventional tillage (CT) were compared in the WF and WSF systems. Available soil water at planting and harvest was measured in 0.3‐m increments to a depth of 1.5 m, and grain yield and water use efficiencies were determined. Water moved deeper in the profile under NT. Compared with CT, twice as much water was stored due to NT in the WSF sorghum profile as in the WF and WSF wheat profiles. An average of 62% of the additional water was found below 0.9 m. As much water was stored in the 11‐mo fallow period prior to WSFNT sorghum as was stored in the 15‐ and 19‐mo fallow periods of WF and SF. No tillage resulted in yield increases 17% of the time in WF, 34% of the time for wheat in WSF, and 60% of the time for sorghum in WSF. For sorghum, the yield of SF was similar to that of WSFNT, whereas SS had the lowest grain yield per planted hectare. Efficient storage of precipitation in WSF prior to NT sorghum and increased sorghum yield make the WSFNT system superior to other systems in this study.