Salliana R. Stetina

Corn Yields Benefit in Rotations with Cotton

Continuous cotton (Gossypium hirsutum L.) was the primary crop for the Mississippi Delta until recently. Corn (Zea mays L.) is now grown on about 1 million acres in Arkansas, Mississippi, and Louisiana, usually in rotation with cotton. This research evaluated corn’s performance in a four-year furrow irrigated rotation with cotton at Stoneville, MS. The experimental design was a randomized complete block with a split-plot arrangement of treatments replicated eight times. Whole plots were cropping sequences assigned at random. Cropping sequences were continuous cotton, continuous corn, corn-cotton-corn-cotton, or cotton-corncorn-cotton. Four adapted corn hybrids and cotton cultivars were grown as subplots beginning in 2000 to 2003. Corn grain yields were greater following cotton than continous corn in 2001 (169 bu/acre vs. 160 bu/acre) and 2002 (126 bu/acre vs. 117 bu/acre). Grain yields from continuous corn differed among years but with no consistency. Hybrids differed in yield among all years but no consistency in these data was noted. Test weights for continuous corn differed among years but were not below the requirement for US No. 2 yellow corn. Weights of 100 kernels did not differ among years or treatments. Economics dictate cropping sequences but corn can benefit from following cotton in rotation.

Responses of Reniform Nematode and Browntop Millet to Tillage, Cover Crop, and Herbicides in Cotton

Cropping practices that suppress reniform nematode (Rotylenchulus reniformis) and browntop millet (Urochlora ramosum) may help minimize losses in cotton (Gossypium hirsutum). The impacts of tillage, a rye cover crop, and application of preemergence and postemergence herbicides on cotton yields, reniform nematode populations, and browntop millet control were investigated from 2005 to 2007 at Stoneville, MS. Cotton yields were highest with conventional tillage and were reduced by rye cover crop. Reniform nematode population densities were not affected by tillage, cover crop, or herbicide treatments. Browntop millet control was highest with conventional tillage combined with preemergence herbicides, and these practices could benefit producers who need to manage this weed. Browntop millet was not controlled as well where a rye cover crop was grown. Management practices are still needed to control reniform nematodes in cotton, but the management practices that suppressed browntop millet did not affect reniform nematode populations and could likely be used without increasing the risk of damage from the nematodes.

Cotton (Gossypium hirsutum) Cultivars Exhibiting Tolerance to the Reniform Nematode (Rotylenchulus reniformis)

A field study was conducted over a two-year period (2006-2007) at the Delta Research and Extension Center, Stoneville, MS, USA to screen selected entries in the 2006 Mississippi Cotton Variety Trials for tolerance to the reniform nematode (Rotylenchulus reniformis). Trials were conducted in nonirrigated fields with primarily sandy loam soils. Though some variability was noted between test locations and years, six of 13 cotton (Gossypium hirsutum) cultivars tested were considered tolerant to the reniform nematode: “Cropland Genetics 3520 B2RF,” “DynaGrow 2520 B2RF,” “Stoneville 5242 BR,” “Stoneville 5599 BR,” “Deltapine 488 BG/RR,” and “Fibermax 960 B2R.” Of these, the first three exhibited yields similar to the productive cultivar “Deltapine 445 BG/RR” in all environments. Though they will not suppress the reniform nematode population, these cultivars can help reduce economic losses attributed to this pathogen in the Midsouth region of the USA.