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A great challenge for agricultural production is to produce more food with less water, which can be possibly achieved by increasing crop water use efficiency (WUE). We systematically reviewed 51 cases from 48 empirical studies with field experimental results on wheat and cotton. We estimated the yield-water use relations under both furrow and micro irrigation systems, compared crop water use to achieve maximum WUE and maximum yield, and evaluated the effects of many influential factors using meta-regression analysis. Our results showed significant effects of micro irrigation adoption, farm management practices focusing on crop, soil and water, and some moderator variables related with the empirical studies on crop WUE. Assessments of the publication selection bias and genuine effects illustrated the application of weighted least squares in conducting meta-regression analysis.

Cover crops have been proposed as a resource that could enhance the effect of no‐till (NT) cropping systems. Crop yield limitations due to cover crops in the U.S. Great Plains are a concern to potential adopters. This research determined the impact of cover crops on crop yield and economic return compared with conventional practices in dryland systems of the Texas Rolling Plains. The study conducted at the Texas A&M AgriLife Chillicothe Research Station evaluated the following treatments: (a) conventional till (CT); (b) NT, and NT with the following cover crops; (c) Austrian winter pea (Pisum sativum L.); (d) hairy vetch (Vicia villosa L.); (e) crimson clover (Trifolium incarnatum L.); (f) winter wheat (Triticum aestivum L.); and (g) a multi‐species mixture. Cotton (Gossypium hirsutum L.) yields, expenses, and returns were determined over a 4‐yr period (2013–2016). Cover crops increased total seed costs compared to CT and NT. Hairy vetch and the multi‐species mixture increased total expenses over CT and NT. However, no significant treatment effect was determined for crop yield or net return among treatments. A multi‐species mixture did not provide an agronomic or economic advantage compared to single species cover crop approaches. Under dryland conditions in the Texas Rolling Plains, these selected cover crops maintained cotton yields without negatively affecting net returns. Other ecosystem services should be considered prior to implementing cover crops in studied cropping systems. Site‐specific research is warranted in regions of the southern Great Plains where water may be more limited than the Texas Rolling Plains.

Abstract:Under two different power structures, where the supplier and the distributor, respectively, are modeled as the leader, this paper studies water pricing strategies in two competing water resources supply chains. We assume that each water supply chain consists of a risk-neutral water supplier and a risk-neutral water distributor. We build different decision models for two competitive water resources supply chains, derive the optimal decision strategies for the water supply chain members, and analyze how competition intensity affects these decisions. Analytical results show that when the supplier is the leader, its water wholesale price is always higher than that when the distributor serves as the leader. On the other hand, the retail price and the two supply chains' channel profits depend on the competition intensity, but are independent of the power structure. To illustrate the proposed models, we apply them to examine the water pricing strategies in the South-to-North Water Diversion Project in China. The results showed significant insights into the pricing strategies of water resources in different routes of this massive water diversion project.

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Core Ideas Stabilized urea improved wheat grain yield and protein in the Southern Plains.Stabilized urea at a higher rate brought higher net profits than untreated urea at all price points.A safe seed‐placed rate for polymer‐coated urea in regional wheat is lower than 30 kg N ha–1.No benefit was observed in splitting nitrogen application in this study. In no‐till wheat (Triticum aestivum L.) cropping systems of the US Southern Great Plains, urea fertilizer is commonly surface broadcast and producers rely on unpredictable precipitation in dryland conditions for incorporation into the soil. Several enhanced‐efficiency fertilizer technologies are designed to reduce N loss in this scenario, though there are not published reports on evaluations of these in regional wheat systems. Here we report on an evaluation of two enhanced‐efficiency fertilizer technologies, polymer‐coated urea (PCU) and urease/nitrification inhibitor‐stabilized urea (SU), which were compared to untreated urea at different application rates (0, 31.5, and 70 kg N ha−1) and timings (at‐planting and split) in two locations differing in soil type (clay loam and loamy fine sand). The fertilizer was broadcast, except for PCU, which was drilled in‐row. The greatest yield was observed with a high at‐planting rate of SU, where yield was 26% greater than with untreated urea and 34% greater than with no fertilizer. Yield improvement with SU was associated with greater grain N uptake efficiency and protein content. The high SU rate brought higher net profits than untreated urea at all price points analyzed and surpassed the no‐fertilizer control as price increased. As might be expected with seed placement, there was substantial crop damage at the high rate of PCU, but even minor damage at the lower rate. The results suggest that a safe seed‐placed rate for PCU in wheat in this environment is somewhat lower than 30 kg N ha−1. No benefit was observed in splitting the N application.