Hidrogel de Acrilamida e Acrilato para estratégias de recuperação de um Argissolo em Processo de degradação

Abstract

The use of hydrogels as soil conditioners is a promising technique for revegetating degraded areas. This study aimed to prove the following hypotheses: the hydrogel increases the macroporosity of the soil; hydrogel degradation increases nitrogen (N) and potassium (K) levels in soil and plants; and hydrogel application to the soil increases microbial biomass. Four greenhouse experiments were carried out with a completely randomized design. In experiment 1, the effect of hydrogel on soil physical attributes, by factorial 6x4, being six hydrogel doses (0, 0.15, 0.30, 0.60, 1.20 and 2.40 g kg-1). and four wetting and drying cycles (0, 3, 6 and 9 cycles), with three repetitions. In experiment 2, the release of N and K from the hydrogel and their absorption by the Ipê purple seedlings, in a 5x4 factorial with five hydrogel doses (0, 0.30,0.60, 1.20 and 2.40 g kg-1) and four evaluation periods (30, 60, 90 and 120 days) with four repetitions. In experiments 3 and 4, the effect of the hydrogel on the soil microbiota in a 5x3 factorial was evaluated, with the same hydrogel doses of experiment 2 at the end of three incubation times (30, 60 and 90 days) with four replications. Experimental data were subjected to analysis of variance, followed by Tukey test (p < 0.05) and regression analysis. In experiments 3 and 4, multivariate analysis of variance, groupings, discriminants and main components were performed. Increasing hydrogel doses and longer wetting and drying cycles decreased soil density, flocculation degree, total porosity and macroporosity, and increased microporosity and available water. The soil with hydrogel doses and submitted to cycles presented lower water retention than the original soil (no dose and no cycle). The increase increased the macronutrient contents, and higher levels of N and P in the soil occurred at 30 and 120 days of application of the product. Hydrogel doses resulted in higher accumulation of N, P, K, Ca and Mg in plant dry matter, especially at 90 and 120 days after seedling transplantation, reflecting growth gains and quality of the evaluated seedlings. Low microbial activity, biomass growth and better biomass efficiency in carbon utilization were found at hydrogel doses 1.2 and 2.4 g kg-1 at 90 days of incubation. Hydrogel doses above 0.3 g kg-1 favored microbial biomass peaking at the 1.9 g kg-1 soil level at 90 days of incubation. Doses from 0 to 0.6 g kg-1 increased microbial activity at 30 and 60 days of incubation, but medium stabilization occurred with higher doses. Total lipid content increased with hydrogel doses.