Growing a crop in place of fallow may improve soil properties but result in reduced soil water and crop yields in semiarid regions. This study assessed the effect of replacing fallow in no‐till winter wheat (Triticum aestivum L.)–fallow with cover, forage, or grain crops on plant available water (PAW), wheat yield, grain quality, and profitability over 5 yr, from 2007 to 2012. Plant available water at wheat planting was reduced the most when the fallow period was the shortest (i.e., following grain crops) or when biomass production was the greatest. Winter and spring lentil (Lens culinaris Medik.) produced the least biomass, used the least soil water, and had the least negative effect on yield. For every 125 kg ha−1 of cover or forage biomass grown, PAW was reduced by 1 mm, and for every millimeter of PAW, wheat yield was increased by 5.5 kg ha−1. There was no difference in wheat yield whether the preceding crop was harvested for forage or left as standing cover. In years with above‐average precipitation, wheat yield was reduced 0 to 34% by growing a crop in place of fallow. However, in years with below‐average precipitation, wheat yield was reduced 40 to 70% without fallow. There was minimal negative impact on wheat yield growing a cover or forage crop in place of fallow if wheat yield potential was 3500 kg ha−1 or greater. Net returns were reduced 50 to 100% by growing a cover crop. However, net returns were increased 26 to 240% by growing a forage crop. Integrating annual forages into the fallow period in semiarid regions has the greatest potential for adoption.

Water is the driving variable in Great Plains agriculture and sustainability depends on efficient use of incident precipitation. Spring and winter wheat (Triticum aestivum L.)‐fallow (SWF and WWF) farming systems, as currently practiced, are not economically sustainable without government subsidies. This paper synthesizes information regarding the water use efficiency (WUE) of intensified cropping systems in cultivated dryland agroecosystems and proposes solutions to ensure sustainablity. Decreasing tillage and maintaining crop residue on the soil is requisite to improved efficiency. No‐till fallow efficiency, the percentage of the precipitation stored during fallow, reached 40% in the early 1970s. However, scientists in the 1980s and 1990s still report fallow efficiencies no greater than 40%, indicating that other major system changes must occur if progress is to continue. Residue levels in the Great Plains usually are < 3 tons/acre and this probably has capped fallow efficiency near 40%. No‐till management of crop residues after spring or winter wheat harvest increases soil water storage in the first portion of the fallow (July to May) compared with conventional fallow management, but the soil in the late fallow period (June to September for winter wheat and June to May for spring wheat) gains no more water, and may even lose water relative to the quantity present in the spring. Overall system efficiency is best evaluated by calculating grain WUE values. Modern no‐till wheat‐fallow (WF) systems, even with maximum fallow efficiencies, only had average grain WUE of 104 lb/acre per in. for spring wheat and 140 lb/acre per in. for winter wheat. WUE for 3‐yr cropping systems, like winter wheat‐corn (Zea mays L)‐fallow or winter wheat‐sorghum [Sorghum bicolor (L.) Moench]‐fallow, increased WUE in Central and Southern Great Plains. Three year system WUE averaged 180 lb/acre per in., a 28% increase compared with WF. In the Northern Plains, continuous spring wheat systems averaged 122 lb/acre per in., a 15% increase compared with SWF. Individual crops within systems had the following potential WUE values: corn = 245 lb/acre per in., grain sorghum =225 lb/acre per in., proso millet (Panicum miliuceum L). = 195 lb/acre per in., spring wheat = 216 lb/acre per in., and winter wheat = 150 lb/acre per in. Maximum system efficiency depends on choosing the most efficient plants for a given geographic area. Intensified cropping systems improve our ability to use precipitation efficiently. However, adoption of higher intensity cropping systems depends more on economic outcomes and government programs than on WUE or environmental effects. Research Question Water is the driving variable in Great Plains agriculture and sustainablity depends on efficient use of precipitation. If Great Plains agriculture is to be economically and environmentally sustainable, systems must be developed that maximize water storage efficiency and grain water use efficiency (WUE). The main objective of this paper was to synthesize existing information rega...

Replacement of fallow in crop–fallow systems with cover crops (CCs) may improve soil properties. We assessed whether replacing fallow in no‐till winter wheat (Triticum aestivum L.)–fallow with winter and spring CCs for 5 yr reduced wind and water erosion, increased soil organic carbon (SOC), and improved soil physical properties on a Ulysses silt loam (fine‐silty, mixed, superactive, mesic Aridic Haplustolls) in the semiarid central Great Plains. Winter triticale (×Triticosecale Wittm.), winter lentil (Lens culinaris Medik.), spring lentil, spring pea (Pisum sativum L. ssp.), and spring triticale CCs were compared with wheat–fallow and continuous wheat under no‐till management. We also studied the effect of triticale haying on soil properties. Results indicate that spring triticale and spring lentil increased soil aggregate size distribution, while spring lentil reduced the wind erodible fraction by 1.6 times, indicating that CCs reduced the soil's susceptibility to wind erosion. Cover crops also increased wet aggregate stability and reduced runoff loss of sediment, total P, and NO3–N. After 5 yr, winter and spring triticale increased SOC pool by 2.8 Mg ha–1 and spring lentil increased SOC pool by 2.4 Mg ha–1 in the 0‐ to 7.5‐cm depth compared with fallow. Triticale haying compared with no haying for 5 yr did not affect soil properties. Nine months after termination, CCs had, however, no effects on soil properties, suggesting that CC benefits are short lived in this climate. Overall, CCs, grown in each fallow phase in no‐till, can reduce soil erosion and improve soil aggregation in this semiarid climate.