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This article in AJ

  1. Vol. 104 No. 1, p. 137-147
    Received: Aug 3, 2011

    * Corresponding author(s): hblanco@ksu.edu
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Summer Cover Crops Fix Nitrogen, Increase Crop Yield, and Improve Soil–Crop Relationships

  1. Humberto Blanco-Canqui *a,
  2. M. M. Claassenb and
  3. D. R. Presleyc
  1. a Kansas State Univ., Agronomy Dep., Agricultural Research Center-Hays, 1232 240th Ave., Hays, KS 67601-9228
    b Professor (Retired), Kansas State Univ., 202 S. Roupp, Hesston, KS 67062
    c Agronomy Dep., Kansas State Univ.,Manhattan, KS 66506


Impact of cover crops (CCs) on winter wheat (Triticum aestivum L.) and grain sorghum [Sorghum bicolor (L.) Moench] yields is not well understood. We assessed crop yield and its relationships with CC-induced changes in soil properties for a 15-yr CC experiment in wheat–sorghum rotation at 0, 33, 66, and 100 kg ha−1 of N application in south central Kansas. Hairy vetch (Vicia villosa Roth) was used as a winter CC from 1995 to 2000, while sunn hemp (SH; Crotalaria juncea L.) and late-maturing soybean [LMS; Glycine max (L.) Merr.] were used as summer CCs in no-till from 2002 to 2008. Summer CCs increased crop yields particularly at low rates of N application. At 0 kg N ha−1, SH increased sorghum yield by 1.18 to 1.54 times, while wheat yield increased by 1.60 times in the first year (2004) after CC establishment relative to non-CC plots. At 66 kg N ha−1, SH had no effects on sorghum yield, but it increased wheat yield in 2 of 3 yr. Cover crops increased soil total N pool by 270 kg ha−1 for the 0- to 7.5-cm depth. Crop yield increased with the CC-induced decrease in soil maximum compactibility (soil's susceptibility to compaction) and soil temperature, and increase in soil aggregate stability, soil organic carbon (SOC) and total N concentration, and soil water content, particularly at 0 kg N ha−1. Principal component analysis (PCA) selected soil compactibility and total N as the best yield predictors. Inclusion of summer legume CCs in no-till fixes N, increases crop yield, and improves soil–crop relationships.

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