Potential of Species of Green Coverage in Entisol

The intensive use of the soil, associated with the application of chemical fertilizers, contribute to degradation processes that affect soil quality and crop production. The use of techniques that contribute to soil conservation and reduction of external inputsis important for the success of the agriculture, and hedging is an alternative. The objective of this study was to evaluate the phytomass production nutrient accumulation and contents, as well as rate of decomposition of different species used as cover plants. The experimental design was randomized blocks, with nine treatments distributed in three blocks. The treatments were: Canavalia ensiformes (L.) DC., Crotalaria spectabilis Roth, Crotalaria ochroleuca G. Don., Crotalaria juncea L., Dolichos lablab L., Stizolobium niveum (Roxb.) Kuntze, Stizolobium aterrimum Piper & Tracy, Neonotonia wightii (Wight & Arn.) J.A. Lackey and Pennisetum glaucum (L.) R.Br. The most recommended species as cover plants are C. ochroleuca and C. spectabilis for they produce more dry matter on the tops, 5.89 and 4.04 kg ha, in addition to greater accumulation of nutrients. C. ochroleuca and C. spectabilis had higher accumulation of N, P, K, Mg and S, and soil coverage with those species can be a good source of green manure. The recommended species for the highest coverage rate are: N. wightii; S. niveum and S. aterrimum. The recommended species for the lowest rate of decomposition are: S. aterrimum; S. niveum; P. glaucum and C. ochroleuca (0.245; 0.260; 0.264 and 0.276% month).


Introduction
The Brazilian Northeast region is characterized by its climatic variability, which, alongside the reduced vegetation coverage, favors the erosive process, reducing the physical, chemical and biological quality of the soil. The use of cover crops has become an efficient practice in keeping the soil covered for longer, as well as promoting the improvement of chemical and physical properties, in addition to keep the soil protected against rainfall impacts. The decomposition and mineralization of this material improves soil fertility, reducing the amount of fertilizers, mainly nitrogen fertilizers, used in crops of economic value (Foloni, Catuchi, Barbosa, Calonego, & Tiritan 2016;Ordóñez-Fernández, Torres, Márquez-García, Moreno-García, & Cabonell-Bojollo, 2018).
The cycle inserted in the ground from sun contribute (Santos, N The presen and nutrie plant mate material (B greater acc Given this contents an

Results
In Figure Vol. 11,No. 11; in the stage wh ey test ( Table 3 sh R 2 (coeffic and the C/N  The fact that the species present similarity in the rate of decomposition may be related to the values of the near C/N ratio, as well as the half-life time (Boer et al., 2007). The half-life (T ½ ), which means the time needed to reach 50% of the dry matter decomposition of each species, is presented in Table 3. Species with higher T ½ are presumed to be used when the objective is to keep the residues under the soil, and species with a lower T ½ when the succession is an agronomic crop, since nutrient decomposition and mineralization is faster (Viola et al., 2013). C. spectabilis presented the lowest T ½ , and S. aterrimum presented higher T ½ ; the highest T ½ may be related to high lignin contents, making it difficult for microorganisms to act and, consequently, slowing decomposition (Viola et al., 2013).
The climate is a fundamental factor for the decomposition process, mainly precipitation and temperature, since both influence the environmental conditions of the soil, therefore, in the greater or lesser microbial activity. According to (Santana, Vieira, Souto, Gondim, & Fonseca, 2011), the type of management interferes with the rate of decomposition, and the incorporation of the material accelerates the decomposition process, as well as precipitation. In the present study, precipitation and temperature were higher from January to May ( Figure 1B), during which time the samples were collected.

Conclusions
The most recommended species to be used as cover plants are: C. ochroleuca and C. spectabilis, since they produce more dry matter on the tops, 5.89 and 4.04 kg ha -1 , and also showed greater accumulation of nutrients.
C. ochroleuca and C. spectabilis had the highest accumulations of N, P, K, Mg and S, and soil cover may be a good source of green manure.
The species recommended for the highest coverage rate are: N. wightii; S. niveum and S. aterrimum.