Atributos químicos e mesofauna em latossolo amarelo da Amazônia central alterado com doses crescentes de biocarvão

Abstract

Biochar (BC) is considered an alternative to improve the soil fertility of some soils due to its effect on physical, chemical and biological properties. Thus, the objective of this study was to evaluate the chemical attributes, mainly the available P, and the dominant groups of mesofauna in a long-term experiment conducted in a distrophyc Yellow Oxisol in Central Amazonia managed with BC. The experiment was carried out at the Experimental Station of the Amazon Research Institute, in Manaus-AM. The experimental design was in randomized blocks, with four doses of BC (0, 40, 80 and 120 t ha-1) and four replications, totaling 16 experimental units. In the useful area of each experimental unit, soil samples were collected, 12 of which were sampled with 19.63 cm² auger, introduced into the soil up to 10 cm deep, for the evaluation of the mesofauna; considering the same depth, four samples with auger for chemical analysis. In the chemical analysis it was determined: active acidity (pH), exchangeable acidity (Al3+) and potential acidity (H+ + Al3+), total N, available P, K+, Fe3+ and Mn2+, exchangeable Ca2+, Mg2 +, total organic carbon (TOC), soil organic matter (MOS); effective cation potential exchange capacity (t), potential cation exchange capacity at pH 7,0 (T), base saturation (SB), percentage of aluminum saturation (m) and carbon and nitrogen ratio (C / N). The extraction of mesofauna was carried out in a Berlese-Tullgren apparatus and separated into taxonomic groups, from which the density of the groups, Shannon's diversity index and Pielou's equitability were calculated. The variables pH, Fe3+, Al3+, Mn2+, MOS, P and the density of the main taxonomic groups were subjected to analysis of variance and the means compared by the Duncan test at the level of 5% probability. Regression equations were adjusted in order to assess: the availability of P as a function of pH, Fe3+, Al3+, Mn2+ and MOS; the density of the groups in function of the attributes of the soil. Also, principal component analysis was performed, taking soil attributes as explanatory variables and group densities as response variables. The highest levels of P (40 t ha-1 of BC), MOS (80 t ha-1 of BC), Fe and Al (120 t ha-1 of BC) and the lowest values pH were found in the presence of BC. Between 0 and 40 t ha-1 of BC the availability P, quantity of MOS and Mn increased and then decreased to 120 t ha-1 of BC. The Fe and Al content increased linearly as the BC dose increased, while the pH in water decreased. 26 mesofauna groups were identified, 24 found in the soil without BC, 20 in the soil with 40 t ha-1 of BC, 22 in the soil with 80 t ha-1 of BC and 18 in the soil with 120 t ha-1 of BC. In the four treatments, 181,217 individuals / m² were collected. Of this fauna, 91.68% was represented by Acari (80.70%), Collembola (6.76%) and Formicidae (4.22%). The densities of the groups did not vary significantly between treatments. The regression analysis revealed a significant decrease in the Shannon diversity index with the increase in the BC dose added to the soil, a similar trend was observed for the C / N ratio and Collembola density, which in turn decreased with the increase in the content of Al3+ in the soil. Formicidae density increased with increasing availability of P in the soil. Through the analysis of main components, a greater association of Collembola, Coleoptera, Symphyla and lesser of Chilopoda and Homoptera was observed with the soil without BC, which was characterized by a higher pH in water value, C / N ratio, lower content of Al3+ (exchangeable acidity) and Mn2+, compared to 80 and 120 t ha-1 of BC. The soil with 40 t ha-1 of BC, which was distinguished by high levels of Ca2+, Mg2+, K+, P available and less aluminum saturation, showed a greater association with Formicidae, Polyxenidae, Pseudoscopionida and lesser with Isopoda, Psocoptera and Hemiptera. Therefore, the results of this study show that the effect of BC on the chemical properties of the soil, determine the number of taxonomic groups of the mesofauna, the density of these groups and the degree of association that each group has with the evaluated treatments; as well as, the increase of the dose of biochar decreases the adsorption of P available in dystrophic Yellow Oxisol.

Keywords: Complexation, phosphorus adsorption, soil invertebrates, soil acidity, soil chemical properties.