Phytometric characteristics and chlorophyll index of “Paiaguás” grass (Urochloa brizantha) as a function of wood ash doses and soil water stress

Abstract

The objective of this study was to evaluate the phytometric characteristics and chlorophyll index of paiaguás grass (Urochloa brizantha) fertilized with wood ash doses and soil water availability. The experiment was carried out in a randomized complete block in a 5x5 fractional factorial scheme (five doses of wood ash: 0, 8, 16, 24 and 32 g dm-3, and five soil water stresses: 4, 8, 16, 32 and 64 kPa), with four replicates. The experimental design was based on the modified central compound, in which 13 combinations of wood ash doses and soil water availability were studied. Each experimental unit consisted of a pot containing 8.7 dm3 of soil and five plants. Three harvests were performed every 30 days after planting, in a 90-day experimental period. At each harvest, plant height, leaf angle, leaf area, stem diameter, and chlorophyll index (SPAD reading) were evaluated. The best results for the phytometric characteristics and chlorophyll index of paiaguás grass were observed in the wood ash dose of 21 g dm-3. There was a reduction of growth and grass chlorophyll content in the soil water tension of 41.20 kPa.