Contribution of Winter Annual Cover Crops in Conservation Tillage Corn Production.

To improve our management of cover crops in conservation tillage systems in dryland agriculture, a two-year study was designed with a local farmer recognized for his conservation tillage successes. The farmer’s primary objective of generating high-residue winter cover crops was to reduce dependence on nitrogen fertilizer. The study was conducted in 2011 and 2012, in North Florida on a commercial farm to evaluate cereal rye (Secale cereale cv. Florida 401) with and without a legume cover crop. Five treatments were tested in 2011, and an additional treatment was added in 2012. Legumes used in the study included: lupine (Lupinus sp. cv. Speckled Blue), crimson clover (Trifolium incarnatum cv. Dixie), and Austrian winter pea (Pisum sativum cv. Frost). Supplemental synthetic fertilizer was applied to cereal rye monoculture cover crop treatments after establishment at a rate of 0, 56 or 112 kg ha^-1, and applied to rye-legume bicultures at a rate of 56 kg ha^-1.  The study was conducted on two different locations on the farm, and each year the crop rotation included peanut followed by winter cover crops followed by corn. Weather conditions were highly variable during the study and included two tropical storms in 2012. Data was collected on soil, cover crop and corn parameters.  Cover crop dry weight biomass was similar among rye plus 112 kg ha^-1 and rye/lupine plus 56 kg ha^-1 in 2011, and was up to 30% greater than remaining treatments, but biomass was similar among all treatments in 2012. Nitrogen contributions estimated from cover crop above-ground dry weight ranged from 74-120 kg ha^-1 N. Corn yields reflected cover crop biomass contributions, and were 18% greater in rye/lupine plus 56 kg ha^-1 N than monoculture rye or rye/lupine without supplemental fertilizer. In general, supplemental fertilizer to winter cover crops was more important to subsequent corn yields in dry years than years with above-average precipitation.