Fertilidade do solo, crescimento e nutrição mineral do eucalipto fertilizado com lodos de efluentes agroindustriais

Abstract

The using of agroindustrial effluent sludge in soil can be an excellent alternative due to the fertilizing and soil conditioner potential because it provides the possibility of achieving increases in essential nutrient contents and growth of eucalyptus plants. However, work using waste from these sources is still scarce. In view of this, the aim of the present work was to evaluate the morphophysiological and edaphic effects using three effluent kinds of sludge from the food industry in the initial growth of a hybrid of Eucalyptus urophylla x Eucalyptus grandis (Eucalyptus urograndis); through the quantification of sludge doses effects on (i) the morphological parameters of eucalyptus, (ii) the macro and micronutrient foliar contents and (iii) the soil fertility and its chemical attributes. The experimental outline was the randomized block in factorial scheme (4x4)+1, with four repetitions, in which the first factor refers to the effluent sludge used (poultry slaughterhouse primary sludge (LPAI), dairy secondary sludge (LSLI) and dairy tertiary sludge (LTLI), all incorporated into the soil; and dairy tertiary sludge in coverage (LTLC)); the second factor were the four doses of each kind of sludge (10, 20, 30, and 40 t ha-1) and a control, without the application of effluent sludge. The experiment was conducted in a greenhouse in pots for a period of 100 days. The results indicate that the application of effluent sludge promoted beneficial effects in the early development of E. urograndis, it influenced leaf nutrient content and increased the chemical attributes related to soil fertility. Better results were found with the use of LSLI, which presented satisfactory results regarding macro and micronutrient foliar contents, higher morphological parameters and soil fertility. Satisfactory results were also observed with the use of dairy tertiary sludge, being that the application in cover provided adequate results regarding the chemical soil attributes and higher levels of P in the vegetal tissue. The application of LPAI resulted in nutritional deficiency of K and low levels of soil element, which caused negative effects on the morphological parameters of eucalyptus in the highest doses tested. Low levels of K in soil were also observed with the application of LSLI and LTLI, although no negative effects were observed on the initial growth of the culture. It is recommended to supplement K mineral in the incorporated application of LPAI, LSLI and LTLI. As for the doses, it is recommended, for secondary and tertiary sludge of dairy, the application of 30 to 40 t ha-1 and, for primary sludge, between 17 and 27 t ha-1. The Pb, Cd, Cr and Cu levels are below the limit of research for agricultural areas, therefore, the residues can be used in an environmentally safe manner in the evaluated doses of 10 to 40 t ha-1.