Winter legume and tillage effects on cotton growth and soil ecology

Field studies were conducted at 2 locations in Alabama during 1984 and 1985 to identify cultural practices which would improve cotton (Gossypium hirsutum L.) stands when plantned no-till into winter legumes. The soils were a Decatur silt loam (Rhodic Paleudult) and a Norfolk sandy loam (Typic Paleudult). The experimental design was a randomized complete block with 4 replications. Whole plots consisted of winter annual legumes (Vicia villosa Roth or Trifolium incarnatum L.) and fallow areas. Split-plot treatments established at cotton planting included conventional and conservation tillage, and fungicide. Soil samples were collected at cotton planting for population determination of Collembola and Acari species, and for estimation of cotton-disease fungus (Rhizoctonia solani) infestation. Collembola populations were greater in the Decatur than Norfolk soils, and higher in legume-mulched than fallow soils by 39 and 72% for the Decatur and Norfolk soil, respectively. Disease infestation in the Decatur soil was 10% higher in legume than fallow plots, and 18% higher in legume than fallow plots in the Norfolk soil. Cotton populations were 19% less in legume than fallow areas, and 25% less with conservation (no-till) than with standard tillage. Bedding improved cotton stands by 21% compared to conservation tillage. Seed-cotton yields from the Decatur soil were consistently high (3798 kg ha⁻¹, and there was no yield response to treatments. Maximum seed-cotton yields at the Norfolk site were achieved with conservation tillage in the fallow area, and conventional tillage in the legume area (both receiving fungicide).