Soil and water losses were evaluated from 1987 to 1995, on a very clayey red dusky latosol, with 0.03 m m-1 slope, of Embrapa-Centro de Pesquisa Agropecuária do Oeste, at Dourados, Mato Grosso do Sul State, Brazil. Soil tillage systems used for growing wheat and soybean in succession were: chisel plow + tandem disk (ES), offset disk + tandem disk (GP), no tillage (PD) and conventional tillage, with no vegetable cover (DE). All tillage operations and seeding were in the up and down hill. PD was the most efficient tillage system to control soil and water losses and was the most productive. GP was the least efficient. Means of soil and water losses for PD, ES, GP and DE were, respectively: 0.8; 2.8; 5.3 and 7.3 t ha-1 year-1, and 27, 80, 112, and 149 mm year-1. Compared to DE, the PD controlled 89% of soil and 82% of water erosion losses, and yielded 17% more soybean and wheat grain than GP. As for wheat, ES was 12% more productive than GP. Rainfall-runoff erosivity factor (R) was 6.411 MJ mm ha-1 h-1 year-1, and the erodibility fator (K) was 0.0045 t h MJ-1 mm-1, reflecting characteristics of high infiltration and high internal drainage of this soil. During the 1994/95 growing season, the highest soil loss period per time unit was from seedbed preparation to seeding soybean, and the period of highest absolute soil erosion losses was from 30 to 60 days after seeding soybean. This shows the great importance of soil cover, specially during the inicial cropping phase, and support the recommendation of the no tillage system for this region.
no tillage; chisel plow; rain-runoff erosivity; soil erodibility