Interações entre resíduos orgânicos e adubações nitrogenadas no cultivo da Urochloa brizantha cv. Marandu e nos atributos do solo

Abstract

The biosolid is a residue generated during the treatment of wastewater at the Sewage Treatment Station (ETE), it is rich in organic matter and nutrientes, but there are limitations to its use. A viable alternative for using this residue is its transformation into biochar through pyrolysis, associating the inherent benefits to biochar, eliminating the presence of pathogens wich is one of the main limitations for its application. Therefore, this study aimed to evaluate whether applications of organic residues and biochars individual or combined with nitrogen fertilization interfere in the soil attributes and in the development of Urochloa brizantha cv. Marandu. Thus, in a first stage, biochars was produced from a dry biosolids sample and a dry sugarcane bagasse sample, separately, through slow pyrolysis at a temperature of 350°C, wich where characterized through physical analysis, chemical and mass balance. In a second stage, a experimente was installed in a completely randomized design (DIC), with a 7x4 factorial scheme and 5 repetitions, and the treatments consisted of 7 substrate compositions namely: control soil (SC); soil + 300 g of pure biosolid (BP); soil + 100 g pure sugarcane bagasse (BCP); soil + 150 g pure biosolid + 50 g pure sugarcane bagasse (BP+BCP); soil + biosolid biochar (BB); soil + 100 g sugarcane bagasse biochar (BBC); soil + 150 g biosolid biochar + 50 g sugarcane bagasse biochar (BB+BBC); and 4 doses of mineral nitrogen fertilization: 0; 12,5; 25 and 50 mg dm-3. In all, 4 cuts were made in the plants at 60, 88, 116 and 144 days after planting. The development of Marandu grass was evatuated through physiological variables: leaf mass production, root mass production, total nitrogen content and organic carbono in plant tissues. As for the soil, the chemical and microbiological atributes were evaluates after the cultivation of Marandu grass. For this, chemical analyzes (determination of pH, organic matter, phosphorus, potassium, magnesium, calcium, aluminium and hydrogen plus aluminium, N-total, N-inorganic and total organic carbon) and biological (basal soil respiration, microbial biomass carbon and nitrogen, dehydrogenase enzyme activity and fluorescein diacetate hydrolysis). The data obtained in the experiment were submitted to analysis of variance using the SISVAR program. For comparison of means, the Scott-Knott test at 5% probability was used (p<0,05). In chapter I, after characterization of the materials, it was found that organic residues and biochars presentes favorable characteristics for agricultural use, mainly BP and BB in terms of fertility, as they showed higher values of nutrientes and CTC. BP and BB can be used as a soil corrector, as they have na alcaline pH of 12.02 and 9.64. In chapter II, the application of materials in the soil showed positive effects Where the soil with insertion of BP at a dose corresponding to 100 kg of N ha-1 showed higher values in relation to the productivity of Urochloa brizantha cv. Marandu. And, soils with the addition of BP and BB, individually or combined with ADN, provided na increase in pH, CTC na base saturation. The addition of organic residues and biochars also evidenced variations for the biological atributes of the soil, where the soil with BP+BCP at a dose corresponding to 100 kg of N ha-1 presented higher value for the enzymatic activities of dehydrogenase and FDA. It is concluded, in general, that the applicability of residues in the soil is a viable practice, because in addition to providing sustainability, by providing a more viable and advantageous destination for residue management, its application in the soil had positive effects in relation to productivity of brizantha cv. Marandu and the atributes of the soil