Allelopathic Effects of Wheat Straw on Cotton Germination, Emergence, and Yield

Because of recently enacted conservation compliance legislation, reduced and no‐till farming systems in which crop residues are left on the soil surface are becoming more important in areas where soils are highly erodible. On the southern high plains of Texas, many producers are planting cotton ( Gossypium hirsutum L.) into wheat straw ( Triticum aestivum L.). This study was conducted to determine the allelopathic potential of wheat residues on cotton germination, emergence, seedling growth, and lint yield. Laboratory bioassays revealed that cotton seedling development was inhibited by aqueous extracts of wheat straw. Cotton cultivars were screened for the ability to tolerate the inhibitive effects of wheat straw in laboratory bioassays and greenhouse pot studies. Tolerant ‘Paymaster 404’ and intolerant ‘Acala A246’ were identified and used in field experiments that were conducted in 1986 and 1987 to determine the influence of wheat stubble residues on their emergence and yield. Major reductions in emergence only occurred when above ground residues were present in the seedbed. Emergence was reduced by an average of 9% for Paymaster 404 and 21% for Acala A246 when wheat stubble residues were present in the seedbed. The allelopathic effect of wheat stubble indirectly influenced lint yield by affecting population densities. The negative effect of wheat stubble on cotton stand establishment can apparently be overcome by; limiting the amount of above ground residues that are incorporated into the seedbed during planting, increasing the seeding rates, and planting tolerant cultivars.