Submitted to: International Journal of Agronomy
Publication Type: Review article
Publication Acceptance Date: 1/13/2011
Publication Date: 4/7/2011
Citation: Zablotowicz, R.M., Reddy, K.N., Krutz, L.J., Gordon, R.E., Jackson, R.E., Price, L.D. 2011. Can leguminous cover crops partially replace nitrogen fertilization in Mississippi delta cotton production. International Journal of Agronomy. 2011:1-9. Interpretive Summary: Unstable petroleum supplies have impacted nitrogen fertilization costs. A three year field study was conducted in Stoneville, MS to assess effects of Austrian pea or hairy vetch cover crops on nitrogen availability and cotton yield grown under reduced-tillage. Cover crops were seeded in October, burned down in early April and nitrogen fertilizer (0, 60 or 120 lb/acre) applied at planting. Plant residues averaged 3600, 7400, and 7100 lb/acre in no-cover crop, Austrian pea, and hairy vetch plots, respectively with 158 lb N/acre in Austrian pea and 136 lb N/acre in hairy vetch attributed to nitrogen fixation. In the first year, both cover crops decreased cotton yield, with no effect of fertilizer N, while cover crop had no effect on cotton yield in the second year but the highest yield was achieved with 120 lb N. In the third year (2007), in no-N plots, cotton yields were 65% higher in both cover crops than no-cover crop. Excess available N from legume cover crops can depress cotton yield in fertile Mississippi Delta soils. Despite leguminous cover crops benefits, extra seed cost challenges development of sustainable low-input cotton production systems.
Technical Abstract: Petroleum prices impacts cotton (Gossypium hirsutum L.) N fertilization cost. A 3-year field study was conducted on a Dundee silt loam to assess the interactions of leguminous cover crops [none, Austrian winter field pea (Pisum sativum L.) or hairy vetch (Vicia villosa Roth] and N fertilization rate (0, 67 or 134 kg N ha-1applied at planting) on nitrogen availability and cotton yield when grown under reduced-tillage management. Cover crops were seeded in October and desiccated with paraquat in early April. Plant residues before desiccation averaged 4.0 Mg ha-1 in no cover crop, 8.3 Mg ha-1 in Austrian pea, and 8.0 Mg ha-1 in hairy vetch, and N content of residues averaged 49, 220, and 183 kg N ha-1, in no cover crop, Austrian pea, and hairy vetch plots, respectively. Sixty-six to seventy-nine percent of the N present in above ground legume residues arose from biological N fixation. In the first year of the study, both cover crops decreased seed cotton yield, with no significant effect of fertilizer N. In the second year, cover crop had no effect on cotton yield, and the highest yield was with N applied at 134 kg ha-1. In the third year, in no N plots, seed cotton yields were 65% higher in both cover crops than no cover crop. However, cotton yields from cover crop N fertilized plots were similar to no cover fertilized plots. These results indicate that either legume can contribute over 150 kg N ha-1with substantial benefits on soil quality. However, the N provided by these cover crops may not be as effective as fertilizer N due to timing of cotton N requirements and release of N from legume residues depressing cotton yield in fertile Mississippi Delta soils.