Cover-crop water use and productivity in the high plains wheat-fallow crop rotation

A long fallow period (similar to 15 mo) in a winter wheat (Triticum aestivum L.)-fallow rotation (W-F) cropping system is meant to store soil water for the following crop but loss of soil quality, low precipitation use-efficiency, and increased cost of fallow management are among its drawbacks. Replacing a portion of the fallow period with a short-season cover crop may alleviate these drawbacks. The objectives of this study were to evaluate available soil water at planting (ASWP(cc)), performance, management, and post-cover-crop fallow efficiency, and available soil water at winter wheat planting (ASWP(ww)) of 12 short-season cover crops. This field study was conducted from 2008 through 2011 at Garden City, KS. The experimental design was a randomized complete block with split-split-plot arrangement. Crop phases were main plot, cover-crop species was the subplot, and cover-crop management method (cover crop left standing or hayed) was the split-split-plot treatment. Results showed ASWP(cc) was greater at spring cover-crop planting than in the fall or winter cover crops. However, water use, productivity, and post-cover-crop fallow efficiency were greatest for sole winter triticale (xTriticosecale spp.) or winter legume-triticale mixtures. In addition, ASWP(ww) was 4-27% more for cover crop left standing than hayed cover crops. Post-cover-crop precipitation storage was positively related to ASWP(ww) but cover-crop biomass had a negative linear relationship with ASWP(ww). We concluded that cover crops left standing stored more soil water than those hayed; however, forage use of the cover crop could provide a dual purpose and economic benefit to improve overall system profitability.