Culturas de cobertura isoladas e/ou consorciadas na produção de massa seca, produtividade de milho e soja, atributos químicos e matéria orgânica do solo

Abstract

The success of no-tillage system depend on the choice of the crops species integrated in the system, once these crops can contribute differently in dry matter accumulation, corn and soybean yield, in soil chemical properties and in the storages of soil organic matter (SOM). Therefore, the aim of this research was to assess the above-ground dry matter production, intercropping winter corn crop yield with Crotalária spectabilis and Brachiaria spp., the soybean yield, the changes in soil chemical properties and quantify the SOM storage in function of cover crops used during two cropping season (2012/2013 and 2013/2014) in the state of Mato Grosso do Sul in Brazilian savannah. The study was carried out in the municipality of Maracaju, in soil classified as Oxisol. The experimental design was in randomized blocks with eight treatments and four replications. The treatments adopted were formed by different cover crops (winter corn crop; intercropping winter corn with Brachiaria ruziziensis; intercropping winter corn with Brachiaria brizantha cv. Marandu; intercropping winter corn with Crotalária spectabilis; B. ruziziensis; B. brizantha cv. Marandu; Penisetum glaucum L. and reference area). The soil samples were collected in two cropping season (2012/2013 and 2013/2014) in 0-5 cm, 5-10 cm and 10-20 cm depth, after desiccation of cover crops. After the samples, it was determined pH, H + Al, K+, P, Ca+2, Mg+2, Al+3 and calculated the sum of base and CEC. For quantification of SOM storage, it were determined the total organic carbon stocks, labile organic carbon, total nitrogen stocks, labile nitrogen stocks, light organic matter in water, carbon management index and also performed the particle size fractionation of SOM. The use of B. brizantha cv Marandu grown single or in intercropping with winter corn crop guaranteed amount of above-ground dry matter over than 6 Mg ha-1 being effective for the success and sustainability of no-tillage system in the state of Mato Grosso do Sul in region of savannah. Based on the results obtained, if the major objective of the intercropping winter corn crop were the winter corn crop yield and the secondary objective were the production of above-ground dry matter, than it is suggested the intercropping winter corn crop with B. ruziziensis. The adoption of B. ruziziensis, B. brizantha cv. Marandu and millet as cover crops promoted increase of Mg2+ and K+ content. The intercropping winter corn crop with Crotalária spectabilis and the reference area promoted higher acidification in soil. There was depletion of pH, H+Al, Ca+2, Mg+2, sum of base and CEC in 2013/2014 cropping season. The adoption of no-tillage system with the use of different cover crops promoted increase in nutrients contents in surface layer and higher acidification in deep soil. In relation to the soil organic matter storages, it was verified that the implementation of intercropping winter corn crop with Crotalária spectabilis, B. ruziziensis and B. brizantha cv. Marandu contributed to labile nitrogen stocks. The organic carbon and labile carbon stocks were more sensitive in detect the alterations in carbon stocks between cropping seasons. The cover crops in no-tillage increases in light organic matter content in water and stabilization of carbon in most system through the time of adoption promoted maintainace and increasing in the total organic carbon stocks and organic carbon linked with soil minerals.