Sustainable Production Systems under No-till in the Cerrado of Brazil - Mato Grosso

Continuous land cultivation with mono-cropping systems tends to promote soil degradation and increase the incidence of crop diseases, pests, and weeds, which in turn reduce crop yield potential. A long-term research project was initiated to look into various aspects of sustainable agricultural systems. The project focuses on crop rotation and other alternatives to generating long-term profitability. Part of this project is dedicated to the study of soil fertility management under these sustainable agriculture systems. Two experiments, one aimed at the production of fiber and the other at grain production, each containing seven different cropping systems, were initiated in 2008.

Results suggest that the production of dry matter of cover crops during the spring, before cotton, is sufficient for good soil protection and recycling of nutrients. Amounts of N, P, K, Ca, Mg, and S recycled by millet and Brachiaria grass were identical, while the amount of K recycled was higher for systems utilizing Brachiaria in the autumn and millet in the spring. The type of cover crop utilized during the spring did not influence cotton yield. The soil density was higher under no-tillage compared to annual soil tillage, but no fiber yield reduction occurred. For farming systems under no-tillage, soil density may be alleviated using Brachiaria grass for periods longer than 12 months, which may be an advantage for farming systems including pasture crops. The use of cover crops after soybean harvest is essential to sustain soil biological activity and nutrient cycling, and crotalaria showed higher levels of N cycled than Brachiaria and millet. Soil P levels were found to be lower in the farming systems with no use of cover crops after soybean, whereas the use of Brachiaria grass showed to increase P level in the soil.

Soybean yields were affected when it followed corn intercropped with Brachiaria. This could be related to immobilization of N in corn and Brachiaria residues. The intensification of the farming system with soybean and corn (second crop) in sequence resulted in higher amounts of nutrient export, which should be taken into consideration when planning fertilizer recommendations. If nutrient balance is not properly evaluated in intensive grain production farming systems it may endanger its sustainability. More conclusive results from this long-term project will be possible with time. Brazil-53