Soil fauna dynamics affected by decomposition of different legume combinations in alley cropping systems in So Lus, Maranho, Brazil

摘要

The objective of this study was to evaluate the temporal composition of epigeous fauna during decomposition of different legume combinations in alley cropping systems. Two legume species with high quality waste Leucaena leucocephala (Leucaena) and Cajanus cajan (Pigeon pea), and two species of low quality waste Clitoria fairchildiana (Sombrero) and Acacia mangium (Acacia), were combined forming six treatments: Sombrero + Pigeon pea (S + PP); Leucaena + Pigeon pea (L + PP); Acacia + Leucaena (A + L); Sombrero + Leucaena (S + L); Acacia + Pigeon pea (A + PP) and control (without legumes). We used the litter bag method to evaluate waste quality. Each bag was filled with 20 g of leaves of the two combined legumes and distributed in the treatments and were withdrawn on the day of pruning and at 3, 6, 10, 15, 30, 60 and 90 days after legume pruning. Two pitfall traps were used to capture epiedaphic fauna in each treatment. Eight evaluations were done based on the date of legume pruning. The initial amount of N was higher in the L + PP treatment (29.31 gKg-1), which showed the highest decomposition constant, providing the fastest release of N in the soil; and presenting the lowest C/N ratio. The highest polyphenol content was found in A + L (4.84%). The soil fauna under different vegetation covers was composed mainly of Aranae, Coleoptera, Diptera, Formicidae, Coleoptera larvae, mites and Collembola; the latter two being the more abundant in all samples. The soil fauna group richness varied during the time of decomposition; the greatest diversity was recorded at 60 days after the legume pruning due to group homogeneity.