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The purpose of this research was to identify the soil organic matter (SOM) fractions changes in a crop rotation system under no-till system (NTS). This research was carried out from October 2010 to February 2014 in a Rhodic Hapludox. The experiment was set up in completely randomized blocks in a factorial design with eight cover crops and three soil depths (0-5, 5-10 and 10-20 cm) with four repetitions. Cover crops: fall-winter corn, intercropping fall-winter corn with Brachiaria ruziziensis, intercropping fall-winter corn with B. brizantha cv. Marandu, intercropping fall-winter corn with Crotalaria spectabilis, B. ruziziensis, B. brizantha cv. Marandu, Pennisetum glaucum L. and set-aside area. The results of SOM granulometric fractionation showed that 6.5% of the total organic carbon (TOC) stocks were in the particulate organic carbon (POC) fraction. The low values of POC observed in this research are associated with the weather condition of experimental site, which shows high temperature and moisture. In relation to the labile carbon (LC), the highest LC stock was observed in 0-5 cm depth, which differed from the 10-20 cm depth. The POC, LC and labile nitrogen (LN) were the SOM fractions that showed to be more sensitive to detect the changes promoted by the cover crops and soil depths in NTS, as well as the carbon management index (CMI). The intercropping fall-winter corn with B. brizantha cv. Marandu and B. ruziziensis were efficient in increasing the CMI in deeper depth (10-20 cm).

INTRODUÇÃOO manejo agrícola é sustentável somente quando a qualidade dos recursos solo, ar e água é mantida ou melhorada, e, no caso do solo, a qualidade depende da manutenção e melhoria de seus atributos físicos, químicos e biológicos, bem como de sua contínua capacidade de produzir alimentos e fibras (Doran & Parkin 1994).Os solos sob Cerrado, no Brasil, em geral, apresentam condições físicas favoráveis à agricul- ABSTRACT RESUMOtura e vêm sendo, gradativamente, explorados com culturas anuais, pastagens e, mais recentemente, reflorestamentos. A mudança da vegetação natural para sistema de exploração agropecuária provoca alterações profundas nos atributos do solo. Quando uma área de vegetação nativa de Cerrado, por exemplo, é convertida em pastagem, ou área de cultivo de grãos, os atributos químicos e microbiológicos do solo são alterados (Costa et al. 2006, Carneiro et al. 2009).

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The purpose of this research was to assess the effects of replacement of native "Cerrado" vegetation (NV) into croplands on soil chemical, physical and microbial properties. This research was carried out on a farm under Rhodic Hapludox soil with different types of agricultural managements systems, and it was used a NV to compare the systems. The experimental design was set up in completely randomized with five treatments and five repetitions. The treatments adopted were several agricultural management systems as follow; NV; CS_Crop system; LS_Livestock system; ICLS-4_Integrated crop-livestock system with four years of implementation; ICLS-8_Integrated crop-livestock system with eight years of implementation. It was assessed some chemical, physical, and microbial parameters in the soil, as soil pH, P content, exchangeable cations, cation exchange capacity, base saturation, cations saturation, soil organic carbon (SOC), soil bulk density (SBD), aggregate stability, microbial biomass carbon (MBC), basal breathing, and microbial quotient. The replacement of NV to ICLS decreased SOC, MBC, soil aggregate stability and increase of SBD. The ICLS improved "Cerrado" soil fertility over time adoption. This integrated system increased the quantity of exchangeable K + and P content in "Cerrado" soil. The ICLS-8 showed soil environment nearby the NV. Even the difficulty in obtaining the same physical and microbial condition of NV, the results of this research point out quite important observations, because just no-till system is not enough to obtain improvement of soil quality and the ICLS can return the soil properties close to native "Cerrado" vegetation.

ResumoAs práticas de manejo do solo exercem importantes influências nas propriedades biológicas e bioquímicas do solo. Neste sentido, objetivou-se com este trabalho avaliar o impacto do manejo do solo nos atributos químicos e microbiológicos, bem como, a influência na produtividade da cultura do milho. O estudo foi realizado no ano agrícola de 2005/06, no Município de Dourados, MS, Brasil. O delineamento experimental foi de blocos casualizados com os tratamentos dispostos em parcelas subdivididas com três repetições, sendo as estações do ano alocados nas parcelas e os sistemas de manejo nas subparcelas. As estações estudadas foram inverno e verão e, os sistemas de manejo no plantio direto foram representados por cinco esquemas de rotação envolvendo as culturas ervilhaca peluda, feijão, aveia, nabo forrageiro, soja, crotalária, milho, sorgo, milheto, girassol e, no plantio convencional, com milho no inverno e soja no verão. A vegetação nativa constituiu um tratamento e, juntamente com o plantio convencional, foi utilizada como ecossistema de referência. Houve correlação positiva entre os teores de Norg, Corg, Porg e C-BMS com os atributos químicos de fertilidade do solo demonstrando a interdependência entre a química e a biologia do solo. A eliminação da vegetação nativa e posterior substituição por sistemas de cultivo reduz o C-BMS. Nas condições de Cerrado, os sistemas de cultivos estudados incrementam o teor de fósforo no solo. A rotação de culturas influencia a produtividade do milho quando cultivado após determinadas espécies de cobertura como crotalária e ervilhaca no sistema de rotação. Palavras-chave: Plantio direto, biomassa microbiana, fertilidade do solo AbstractSoil management practices exert important influence on biological and biochemical properties of soil. This work aimed to valuate the impact of crop rotation on soil biochemical and microbiological attributes, as well and influence on corn crop yield. The experiment was carried out during 2005/06 crop season, in Dourados -MS, Brazil. Experimental design was randomized blocks with treatments established in subdivided plots with tree replications, which seasons were plots and management systems were sub-plots. Studied seasons were winter and summer and no tillage systems were represented by five crop rotation

The purpose of this study was to assess the changes in soil chemical properties affected by the cover crops cultivated in crop rotation in short-term of no-till implementation under Rhodic Hapludox soil. This research was carried out from October 2010 to February 2014. The experiment was set up in completely randomized blocks in a factorial design with eight treatments (cover crops) and three soil depths (0-5, 5-10 and 10-20 cm) with four repetitions. The cover crops were: fall-winter maize (T 1), intercropping fall-winter maize with B. ruziziensis (T 2), intercropping fall-winter maize with B. brizantha cv. Marandu (T 3), intercropping fall-winter maize with Crotalaria spectabilis (T 4), B. ruziziensis (T 5), B. brizantha cv. Marandu (T 6), Pennisetum glaucum L. (T 7) and fallow (T 8). The T 6 and T 7 affected exchangeable Mg +2 , it was observed higher exchangeable Mg +2 in T 6 (2.39 cmol c dm-3) and T 7 (2.43 cmol c dm-3) in comparison to T 1. The phosphorus content showed interactive effect between cover crops and soil depth. In the comparison among the depths, the P contents were higher in 5-10 cm, which showed improvement of 24.6% and 25.2% in comparison to 0-5 and 10-20 cm layers, respectively. The cover crops evaluated in this research affected the exchangeable Mg +2 and K + , as well as Mg +2 and K + saturation. The P content changed in response of cover crops, which was important to observe that this nutrient may increase the content with adoption of cover crops in no-till system. The species used in this research might be recommended to integrate a crop rotation system with the possibility of increasing P availability in topsoil depth in no-till system.