Crotalaria juncea L. as green manure intercrop in corn.

Nitrogen content of Crotalaria juncea decreased with age at all seeding rates. Available soil nitrogen continued to increase until seven weeks after incorporation of the legume into the soil. Release of nitrogen from the organic biomass was faster when C. juncea was incorporated at 30 than at 45 or 60 days after planting. Rapid increase in available nitrogen in the soil was noted within the first, first to the second and fourth to the sixth week after incorporation of Crotalaria at 30, 45 and 60 days after planting, respectively. Percent nitrogen of C. juncea and nitrogen content of index leaves of corn were not significantly affected by seeding rates of Crotalaria and inorganic nitrogen sidedress fertilization. However, nitrogen uptake of the index leaves of corn was significantly higher at 40 and 60 than at 20 kg/ha seeding rate of Crotolaria. Comparable grain yield were obtained from corn plants supplied with 20 to 100, 40 to 100 or 100% of the recommended inorganic nitrogen as sidedress supplemented with Crotalaria at 60, 40 or 20 kg/ha seeding rates, respectively. Seeding rate of 40 kg/ha C. juncea plus handweeding resulted in higher fresh and dry weight of Crotalaria, nitrogen content of index leaves of corn, nitrogen uptake of corn leaves at silking stage, grain yield and ear length of corn than 20 kg/ha seeding rate of the legume without weed control. Incorporation of C. juncea green manure intercrop at 30 DAP [days after planting] by two hilling up operation or by uprooting and spreading Crotalaria at the base of corn plants followed by one hilling up, resulted in higher nitrogen uptake of corn leaves at silking stage, green yield and number of kernel rows per ear of corn. Significant interaction between weed control and seeding rate of Crotalaria was noted on percent N of index leaves of corn, grain yield, ear length and number of kernel rows per ear of corn. Significant interaction between method of incorporation and seeding rate of Crotalaria was also noted on number of kernel rows per corn ear.