AGRICULTURAL SYSTEM UNDER IRRIGATION

A field experiment was conducted at the National Rice and Bean Researc h Center of EMBRAPA, Goiania-Goias, Brazil, during four consecutive ye ars under sprinkler irrigation using center pivot. The objective of th is study was to evaluate effects of plowing at different depths (15 an d 30 cm), fertilizer levels (200 and 400 kg ha-1) and crop rotation (R 1 = rice-bean; R2 = corn-bean and R3 = rice-wheat-corn-bean) on grain yield, and physical and chemical properties of soil. In general, conce ntrations of Al, Ca+Mg, P, K and MO in soil decreased during the exper imentation period with the agricultural system employed. Under treatme nt of plowing at 30 cm depth, bulk density at 20 and 30 cm depths were lower as compared to initial values. Plowing treatment at 30 cm depth produced higher grain yield of rice in rotation with wheat-corn and b ean as compared to rotation with bean. Bean yield was lower after corn than after rice. Plowing depth had no effect on yield of corn, bean a nd wheat. Higher yields of rice, corn, bean and wheat were obtained at higher fertilizer level. Agricultural system with highest rentability was corn-bean rotation.