Agronomic effect of soil tillage, no-tillage and crop rotation on yield ofirrigated common bean

The objective of this study was to evaluate the agronomic effect of soil ti llage and crop rotation on grain yield of common bean (Phaseolus vulgaris L .) irrigated by central pivot. The study was conducted at the Embrapa-Centr o Nacional de Pesquisa de Arroz e Feijao, in a Dark-Red Latosol with clay t exture, during six consecutive years. Basic experiment was a 4 x 6 factoria l, having a completely randomized block design with subdivided plots. Soil tillage systems were: P1 -moldboard plough (November-December), alternated with harrow disc (May-June); P2-moldboard plough; P3 - harrow disc, and P4 - no-tillage. The crop rotations used were: R1 - rice-common bean; R2 - cor n-common bean; R3 - soybean-wheat; R4 - soybean-wheat-soybean-common bean-r ice-common bean; R5 -rice associated with Calopogonium mucunoides-common be an; and R6 - corn-common beancorn-common bean-rice-common bean. The crop ro tations R1, R2, R3, and R5 were annual and R4 and R6 were triennial; in thi s study, only rotations with common bean were evaluated. Rice, corn and soy bean were sown in November/December (summer) and common bean and wheat in M ay/June (winter). Grain yield of common bean was influenced by soil tillage and crop rotation. Yield was higher under soil prepared with moldboard plo ugh in combination with summer sowing and prepared with harrow disc in wint er sowing. Common bean grain yield was higher when biannual sowing was done in the same area in rotation with rice/C. mucunoides and rice, and lower i n rotation with corn. Irrigated common bean crop was economically viable as a function of soil tillage and crop rotation and economic return varied fr om 67% to 97%.