Monday, November 13, 2006 - 2:15 PM

Cover Crop Biomass Effects on Early Season Weed Establishment.

Monika Saini, Auburn Univ, Dept. of Agronomy & Soils, 202 Funchess Hall, Auburn, AL 36832, Andrew J. Price, USDA-ARS, 411 S. Donahue, Auburn, AL 36832, and Edzard van Santen, 202 Funchess Hall, Auburn University, Auburn University, Dept. of Agronomy & Soils, Auburn, AL 36849-5412.

Use of  winter cover crops is an integral part of the conservation systems in corn (Zea mays L.) and cotton (Gossypium hirsutum L.). On-going field experiments to evaluate weed suppression provided by winter cover crops in conservation tillage corn and cotton rotation were started in 2003 at the Alabama Agricultural Experiment Station’s E.V. Smith and Tennessee Valley Research and Extension Centers. In 2004, a similar experiment was also established at the University of Florida’s West Florida Education and Research Center. Rotation for winter cover crops included clover (Trifolium incarnatum L.) preceding corn and rye (Secale cereale L.) preceding cotton. Both covers were planted at five different planting dates with the median date corresponding to the 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 soil temperature.  Results showed a dramatic decrease in biomass production with every week’s delay in winter cover crop planting and subsequently can have a negative bearing on the cover crop benefits. More than ten times difference in biomass produced by clover was observed when clover was planted on the earliest date 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, 8 times higher compared to the treatment with greatest rye biomass. Weed biomass sampled in clover were less than in rye even though the difference was only 34 kg/ha in case of clover. Data for the first two years show no significant relationship between cover crop biomass and the cash crop yield.