COVER CROP RESIDUE EFFECTS ON EARLY-SEASON WEED ESTABLISHMENT IN A CONSERVATION-TILLAGE CORN-COTTON ROTATION

Use of winter cover crops is an integral component of conservation systems in corn (Zea mays L.) and cotton (Gossypium hirsutum L.). A field experiment was initiated in 2004 to evaluate weed suppression provided by winter cover crops in a conservation-tillage corn and cotton rotation. Rotation for winter cover crops included clover (Trifolium incarnatum L.) preceding corn and rye (Secale cereale L.) preceding cotton. The covers were planted at five different planting dates based on thirty year average first frost. Termination dates in the spring were 4, 3, 2 and 1 week prior to cash crop planting, based on thirty year average historical soil temperature. It was observed even a week’s delay in winter cover crop planting can severely impact the biomass production and thus have a negative bearing on the cover crop benefits. More than ten times difference in cover biomass produced by clover was observed when the covers were planted on the earliest and terminated on last date compared to late planting and early termination. Rye produced almost eight times more biomass in the same comparison. Correspondingly, weed biomass was 556 kg/ha in the treatment with least rye biomass, eight times higher compared to the treatment with greatest rye biomass. Though the difference was only 34 kg/ha in case of clover, it is important to mention that weed populations observed in clover were less than in rye