Crimped Cover Crop Legume Residue Effects on Sweet Corn (Zea mays L.) Yield in Puerto Rico.

Crimped legume residue can control weeds and supply N for sweet corn production if biomass is sufficient.  Three sweet corn (Zea mays L.) open pollinated variety “Sureweet 2011” plantings (April, 2013; July 2013; February 2014) were conducted on an Oxisol (very fine, kaolinitic, isohyperthermic and Typic Eutrustox) in Puerto Rico to evaluate biomass and N accumulation of dwarf mucuna (Mucuna pruriens) and crotalaria (Crotalaria juncea; cv Tropic sun) crimped 6-wk after planting; and determine sweet corn production drilled on crimped dwarf mucuna and Tropic sun vs. conventional tillage (CT; corn fertilized with 56 kg ha^-1 N).  There was a date effect (P<0.05) on biomass and N accumulation. Biomass and N for July planting was higher for dwarf mucuna compared to Tropic sun, but N accumulation was lower than the N applied in CT.  There was a main effect (crimped legumes and CT) and planting date x crimped legumes and CT interaction (P<0.05) for ear size and seed yield, and a trend for ear yield (P=0.08).  However, there was no effect of either planting date or crimped legumes or CT on insect damage.  Crimped dwarf mucuna had uniform ear size across planting dates, and was similar to CT on the April planting, but had larger ear size (15.5 cm) for the July planting.  Seed yield for CT was higher in the first planting, but dwarf mucuna surpassed yield for CT and Tropic sun by 25 and 72%, respectively, for July planting.  Results suggest that dwarf mucuna, consistently provides uniform ear yield throughout the year, and also higher marketable seed yield in July planting. In conclusion, planting date affected biomass and N accumulation and also ear size and marketable seed yield. On the other hand, dwarf mucuna had better agronomic performance and was comparable to CT.