Potassium fertilization effects on cotton lint yield, yield components, and reniform nematode populations

Cotton (Gossypium hirsutum L.) lint yields have not changed appreciably during the last decade. Because more and higher infestations of reniform nematodes (Rotylenchulus reniformis) have been identified in mid-southern USA fields, this nematode might be a mitigating factor in the cotton yield stagnation. The objectives were to determine how varying rates of K fertilization interacted with different cotton genotypes to influence dry matter partitioning, lint yield, fiber quality, and reniform nematode populations. Nine cotton genotypes were grown in the field under two levels of K fertilization (0 and 112 kg K ha(-1)) and two levels of aldicarb [2-methyl-2-(methylthio)propionaldehyde 0-methyicarbamoyloxime] application (0 and 1.68 kg a.i. ha(-1)) from 1999 through 2001. Reniform nematode numbers and above-ground dry matter partitioning were determined at various times in the growing season. Lint yield, yield components, and fiber quality were determined at the end of the season. Cotton grown with K fertilization hosted a 12% larger post-harvest population of reniform nematode than the unfertilized control plants. Plants grown without K fertilization averaged a 10% greater specific leaf weight than the K fertilized plants. Of the 9 genotypes grown, only PayMaster 1218BR increased lint yield (10%) in response to K fertilization. An interaction between aldicarb application and K fertilization for lint yield during the 2000 growing season indicated that both reniform nematode parasitism and insufficient K fertilization may impose limitations to lint yield production. Large reinform nematode populations may be suppressing the yield response to K fertilization. Production practices that encourage robust plant growth may enhance proliferation of existing reniform nematode populations.