Wood ash and water availability in the production of Paiaguás-grass

Abstract This study evaluated the production of Paiaguás grass (Urochloa brizantha) as a function of wood-ash doses and water availability in the Cerrado Oxisol. The experiment was carried out in a greenhouse with a randomized block design in a fractioned 5x5 factorial scheme, corresponding to five wood-ash doses (0; 8; 16; 24 and 32 g dm-3) and five soil water-availability scenarios (4; 8; 16; 32; 64 kPa) with four repetitions. The experimental design was based on the modified central compound and consisted of 13 treatments of wood-ash doses (g dm-3) and soil water-availability scenarios (kPa): 0-4; 0-16; 0-64; 8-8; 8-32; 16-4; 16-16; 16-64; 24-8; 24-32; 32-4; 32-16; 32-64. Soil volumetric moisture was monitored daily by means of the Diviner 2000 Capacitance Probe® for soil water replenishment according to the treatments. In 30-day intervals, three cuts were performed in the aerial part of the plants evaluating dry mass of leaves, stems, aerial part, number of leaves and of tillers. Data were subjected to analysis of variance and when significant to regression analysis, both up to 5% of error probability, through the statistical program SISVAR and response surface study using SAS. The combinations of wood ash doses with water soil tensions influence the productive characteristics of Paiaguás grass. Fertilization with wood ash reduces the effect of water stress on Paiaguás grass and this residue may be a viable alternative to partial replacement of mineral fertilization and safe disposal in the environment.