Long-term tillage and crop rotation effects on soil chemical properties of a Rhodic Ferralsol in southern Brazil

The assessment of the changes associated with immediate and long-term tillage and crop management practices under different agro-ecological zones is vital to the selection and establishment of appropriate soil conservation and management measures. In this study, three tillage practices, namely no-tillage (NT), chisel plough (CP), and conventional tillage (CT) were imposed in 1983 on corn (Zea mays L.) and soyabean (Glycine max L. Merrill) plots on a continuous rotation in a Rhodic Ferralsol (Typic Haplorthox) of Sao Paulo, Brazil. Soil was limed twice to correct base saturation decline in 1985 and 1994. Soil chemical properties were determined at four depths (0-0.05, 0.05-0.1, 0.1-0.2 and 0.2-0.3 m) in 1986 and 1995, one year after each liming. Results showed that in 1986, significantly higher amounts (p < 0.05) of organic matter (OM), extractable P and K occurred at the 0-0.05 m soil depth under the NT practice. Eleven years later, the same effects of the NT on the parameters were extended to the 0.05-0.1 m soil depth. Differences (p < 0.05) in Ca, Mg, pH, base saturation and cation exchange capacity were also obtained in the order NT > CP > CT in 1986 and NT > CT = CP in 1995 at the 0-0.05 m soil depth. Below the 0-0.05 m depth, no significant variation in soil pH occurred among the treatments in spite of Lime application, Significant decline in extractable Mg occurred at the 0.1-0.2 m depth in NT compared with CP and CT. Crop rotation factor did not have evident influence in nutrients status in 1986 and 1995, except for 0-0.2 m depth in 1986 where continuous corn (CC) and rotation corn (SC) significantly reduced P availability. The OM status at the four depths studied, which declined in all treatments over time, tended to be higher in the CC and SS practices than in the CS and SC practices in 1986 and 1995. These changes in soil chemical properties did not result in differences in corn and soyabean grain yields. (C) 1999 Elsevier Science B.V. All rights reserved.