Long-term effect of different soil management systems and winter crops on soil acidity and vertical distribution of nutrients in a Brazilian Oxisol

摘要

"Strategies" to sustain crop productivity by reducing the fertilizer and lime demands must be developed. The use of plant species that use more efficiently the soil nutrients and tillage systems that provide nutrients accumulation in more labile forms are prerequisites for sustainable agroecosystems. This study aimed to evaluate the long period effect of cultivating different winter species under different soil management systems on vertical distribution of soil nutrients and the soil acidity distribution in soil profile. The experiment was established in 1986 with six winter treatments (blue lupine, hairy vetch, oat, radish, wheat and fallow) under conventional tillage (CT) and no-tillage (NT) in a very clayey Rhodic Hapludox in Southern Brazil. As a result of 19 years of no soil disturbance, soil chemical attributes related to soil acidity and the availability of P and K were more favorable to crops growth up to 10 cm in the soil under no-tillage than in the conventional tillage. On other hand, lime applications in low doses on the soil surface were not efficient in neutralizing the aluminum toxicity below 10 cm depth. It shows that repeated use of lime on the soil surface under NT system can be a viable alternative strategy only when soil acidity and aluminum toxicity in subsurface has been previously eliminated using the adequate amount of lime and incorporating it into the arable layer. Moreover, in the conventional tillage system P and K availability were higher below 10 cm depth compared to the no-tillage system. Even after 19 years of no soil disturbance in the NT system the available P content below 10 cm soil layer was lower than the optimal content of available P recommended to cash crops. The reduced surface K application over time was sufficient to gain adequate crop yields and to maintain the optimal content of soil available K in both soil management systems. The effects of soil management systems were predominant on the soil acidity attributes, and no effects of winter cover crops were observed on soil acidity attributes. Black oat and blue lupine were more efficient in P cycling, increasing the soil available P content especially in the surface soil under NT. The lower amount of biomass produced over time when no cover crops were used in the winter period resulted in lower P and K availability in the soil, showing the important role of growing winter species to maintain soil fertility