Soil fauna play an important role in ecosystems, and in this context, it is important to better understand how the abiotic and biotic drivers of these organisms interact. We hypothesize that soil fauna are affected by different soil management practices, which has an influence on maize grain yields. The aim of this study was to evaluate the structure of soil fauna under different soil management practices and their associations with maize grain yield. The experiment was conducted in Maranhão, Brazil, in an area divided into 24 plots of 4 × 10 m in a randomized block design with six treatments with four replicates (R). Pitfall traps were placed in the area. The treatments were Leucaena leucocephala-Leucaena (L), nitrogen (N), humic acid + nitrogen (HA + N), nitrogen + Leucaena (N + L), humic acid + Leucaena (HA + L) and humic acid + nitrogen + Leucaena (HA + N + L). The soil fauna dominance, abundance, richness, Shannon-Wiener diversity index, Pielou evenness index and maize grain yield were determined. Formicidae was clearly affected by management with Leucaena, while Coleoptera was affected by management with nitrogen. Despite this, Isopoda and Diplura were the only groups associated with the maize yield. Although fauna abundance did not differ among treatments, it was related to the yield. This study confirms that the abundance and some taxa of soil fauna can influence yield and that these organisms can be used to increase agricultural sustainability.

Nutrients contained in soil play a fundamental role in plants development. Then, we hypothesize that different soil fertilization regimes modify soil chemical attributes and maize grains yield. This study aimed to evaluate soil chemical attributes in different soil fertilization regimes and their relation to maize grains yield. The experiment was performed in Maranhão state, Brazil. The area was divided into 32 plots of 4x10 m with seven treatments and the control, with four replicates (R) in a randomized block design. The following treatments were performed: Gliricidia sepium – gliricidia (G), potassium (K), humic acid (HA), humic acid+potassium (HA+K), potassium+gliricidia (K+G), humic acid+gliricidia (HA+G), humic acid+potassium+gliricidia (HA+K+G) and uncovered soil (US). Each plot was cropped with maize (Zea mays L.) and the grains yield was estimated. Soil samples were collected from each plot at depths of 0–5 cm, 5–10 cm and 10–20 cm. Potential acidity, pH, soil organic carbon (SOC), exchangeable K+, Ca2+ and Mg2+, available P, cation exchange capacity (CEC), sum of basic cations (SBC) and base saturation (BS) were determined. One-way ANOVA with Duncan post-test and principal component analysis (PCA) were used. Exchangeable K+, Ca2+ and Mg2+, pH and CEC were related to maize grains yield in upper soil layer especially in plots with gliricidia. Then, this research confirms the hypothesis that different soil fertilization regimes modify soil chemical attributes and maize grains yield.

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The research compared biomass production and nutrient release in an alley cropping system in two collection methods, the litterbag method and the direct collection method (Morley, Bennett, & Clark, 1964). The system was implemented in 2015 at 2017, at the Maranhão Federal University, Maranhão, Brazil. The experiment was a randomized block design with four treatments, consisting of leucaena+sombreiro (Leucaena leucocephala and Clitoria fairchildiana), leucena+acacia (Leucaena leucocephala and Acacia mangium), gliricidia+sombreiro (Gliricidia sepium and Clitoria fairchildiana) and gliricidia+acacia (Gliricidia sepium and Acacia mangium). In order to determine the remaining dry matter, nutrient release (N, P, K, Ca, Mg and Mn), the decomposition constants and the half-lives times of plant residues, 100 g of fresh material were conditioned in litterbags (50 g of each species), arranged on the soil surface. The second method was done by randomly throwing a collector on each plot in the same dimensions of the litterbags (0.40 x 0.40 m) and collecting the litter. For the two methods samples were collected at 0, 30, 60, 90 and 120 days after the start of the experiment. The litterbags method showed a higher C/N ratio at day 30 up to 120 days, which implies that this method is providing a different environment from the litter, where it would be overestimating the C/N ratio and retarding the decomposition. The G+S and G+A combinations were more rapidly decomposed than the combinations of L+S and L+A. The following order of release was established for the litterbags method: P > N > K > Ca > Mn > Mg, and for the method of collecting the litter: N > P > Ca > Mg > K > Mn.