Compactação do solo e adubação com cinza vegetal no cultivo de Urochloa brizantha CV. Paiaguás

Abstract

Soil compaction caused by animal trampling on pasture is a recurring problem, causing the reduction of crop productivity, therefore, the application of agro-industrial residues from the burning of vegetal biomass can improve the chemical properties as well the physics of the soil. The objective of this study was to evaluate the effect of the soil density, associated with the wood ash doses in the performance of Paiaguás-grass in a dystrophic Red Latosol. The experiment was performed at the Federal University of Rondonópolis, in a greenhouse from the Post- Graduation Program in Agricultural Engineering. The experimental delineation was on randomized blocks, with a 5 x 5 factorial scheme, with five levels of density (1.0, 1.2, 1.4, 1.6 and 1.8 Mg m-3 ) and five doses of wood ash (0, 8, 16, 24, 32 g dm-3 ), with four replications, totalizing 100 experimental units. Each experimental unit was built with a PVC (polyvinyl chloride) vessel with two isometric rings. The vessels have an internal diameter of 192 mm and a height of 200 mm, totalizing 6.28 dm³ of soil. The 0.5cm layer was compacted with an auxiliary hydraulic press (P15ST, BOVENAU), while the treatments and the lower layers were filled with soil equivalent to a density of 1.0 Mg m-3 . Fertilization with nitrogen was made in all experimental units with 200 mg dm-3 of nitrogen, divided by three applications, with the respective doses, 50, 75 and 75 mg dm-3 , at the 7th, 14th and 21st day after grass emergence. The evaluations were made in each cut of the plant, with a lapse of 30 days. The analyzed variables were the chemical characteristics of soil, nutritional characteristics of plants, phytometric characteristics and productive characteristics. Data were submitted to analysis of variance and regression, both up to 5% error probability, using the R Studio Software. The interaction between the wood ash dose and the soil density when they were present showed that the best development to the grass occurred between an average dose of 22.37 g dm-3 for a soil density of maximum 1.3 Mg m-3 . A dose of wood ash close to 20 g dm-3 promotes the highest production of dry mass of the aerial part of the Paiaguás- grass. The maximum production of the highest dry mass of the aerial part (6.34 g pot-1 ) was obtained with the wood ash dose of 20.42 g dm-3 and the root development of Paiaguás- grass was superior on soils fertilized with wood ash doses of 16.52 g dm-3 . About the levels of soil density, the dry mass of leaves, stems + sheaths and aerial part showed higher production until the soil density of level 1.2 Mg m-3 for Paiaguás- grass. The fertilization with wood ash for the development of Paiaguás-grass was positive, being able to be used as a corrective and alternative fertilizer to the grass crops. The increase of levels of soil density damages considerably the growth and development of Paiaguás-grass.