COTTON YIELD AND FIBER QUALITY RESPONSE TO GREEN MANURES AND NITROGEN

The quantity and availability of N from green manures will considerabl y affect the N management of a succeeding cotton (Gossypium hirsutum L .) crop. This study was conducted to determine the N supplying capacit y of crimson clover (Trifolium incarnatum L.), Austrian winter pea [Pi sum sativum subsp. arvense (L.) Poir.], and rye (Secale cereale L.) to cotton and their influence on cotton yield and fiber properties. Gree n manure treatments (and a fallow check) with fertilizer N levels of 0 , 56, 112, and 168 kg ha-1 were compared for 3 yr on a Norfolk loamy s and (fine-loamy, siliceous, thermic Typic Kandiudult). Soil moisture a t planting was similar among the four green manure treatments. At the 0 N level, the legumes generally had higher soil NO3-N than rye or fal low. Cotton grown following clover and pea with 0 kg ha-1 added N had petiole NO3-N levels similar to those of rye and fallow with 56 kg N h a-1. Fertilizer N had no influence on cotton yield in the pea winter c over treatment. A quadratic regression equation best described the lin t yield response following clover. For both rye and fallow treatments, yield plateaued at 56 kg N ha-1. Green manures had little influence o n fiber properties. The results indicate that legumes supply adequate but not excessive N for modern cotton production and that incorporatio n of rye into the production system does not affect N fertilization re quirements.