MONITORING CHANGES IN THE CHEMICAL PROPERTIES OF AN OXISOL UNDER LONG-TERM NO-TILLAGE MANAGEMENT IN SUBTROPICAL BRAZIL

In tropical areas, soil chemical properties are most often studied in relationship to the type of tillage system. This article presents data of the long-term effects of no-tillage (NT) management systems on the soil chemical properties of an oxisol in subtropical Brazil. The study area was on a commercial farm where NT systems had been adopted in 1978. Soil samples were collected annually from 1983 to 1994 after winter crop harvest in 16 fields and at depths of 0.0 to 0.1 m and 0.1 to 0.2 m. Organic C, exchangeable calcium, magnesium, potassium, extractable phosphate, and pH were measured. Soils were grouped by a multivariate statistical agglomerative hierarchical method into five classes (I-V) based on statistical similarity to assess annual changes in soil chemical properties. This study shows that it is possible to maintain good soil chemical properties under operational NT systems in these subtropical conditions. This study also demonstrated the importance of sequence of crops for maintaining acceptable levels of soil organic matter and good soil chemical properties.