Integrating Legumes as Cover Crops and Intercrops into Grain Sorghum Production Systems. (1st July 2018)

• Record Type: Journal Article
• Authors: Neely, Clark B.; Rouquette, F. Monte; Morgan, Cristine L.; Smith, Gerald R.; Hons, Frank M.; Rooney, William L.
• Is Part Of: Agronomy Journal. Volume 110:Number 4(2018)
• Page Start: 1363
• Page End: 1378
• Publication Date: 2018-07-01
• Subjects: Agronomy -- Periodicals; 630
• DOI: 10.2134/agronj2017.05.0293
• Languages: English
• ISSNs: 0002-1962

Abstract

Abstract : Core Ideas: Intercropping cowpea with grain sorghum dramatically decreased sorghum grain yield. Clover green manure only increased sorghum grain yield 1 out of 3 yr. Fertilizer effects likely masked by mineralized organic matter from plowing of perennial pasture. Crop residue decomposition was mostly unaffected by treatments. Crop residue decomposition was largely driven by residue C/N ratios. Legumes fix N, reduce fertilizer inputs for primary crops, and contribute C to soil organic matter (SOM), which benefits soil productivity and sustainability. Objectives of this study were to (i) maintain grain sorghum [ Sorghum bicolor (L.) Moench] yields while decreasing N fertilizer requirements and build SOM using a temperate legume cover crop and tropical legume intercrop; (ii) quantify soil water usage between legume treatments and N fertilizer rates; and (iii) evaluate treatment effects on residue decomposition of each crop. In Overton, TX, crimson clover ( Trifolium incarnatum L.) and cowpea [ Vigna unguiculata L. (Walp)] were used as green manure and an intercrop, respectively, with grain sorghum. Four N fertilizer rates of 0, 45, 90, and 135 kg ha −1 were randomly assigned within a four replicate split‐split plot design on a Lilbert loamy fine sand. From 2010 through 2012, intercropped cowpea decreased sorghum grain yield between 77 and 93% compared to monocropped sorghum. Clover green manure increased sorghum grain yield 21% over winter fallow in 2012, but not significantly ( P = 0.22). After 3 yr, soil organic C (12.4 g kg −1 ) and soil N (1.1 g kg −1 ) were 18% ( P = 0.01) and 21% ( P = 0.01) higher, respectively, for clover green manure compared to fallow at 0 to 15‐cm depth. Crop residue decomposition was relatively stable across years and only intercropping showed small increases in decomposition of grain sorghum residue. Overall, clover green manure proved to be a more sustainable choice than intercropping cowpea from both a yield and soil perspective.