GROWTH AND PRODUCTIVITY OF COWPEA FERTILIZED WITH BIODIGESTER SEPTIC TANK EFFLUENT

Abstract

This study aimed to evaluate the growth and grain yield of cowpea fertilized with effluent from a biodigester septic tank. The experiment was conducted from March to June 2009 in the municipality of Gurupi, Tocantins State, Brazil. The experiment used a randomized block design, with five treatments and four replicates. Four treatments with fertilizer applications of effluent from a biodigester septic tank (T20 with 20 mm effluent, T16 with 16 mm effluent, T12 with 12 mm effluent, and T8 with 8 mm effluent), plus a control with NPK fertilizer were tested. The following parameters were determined in the growth analysis: dry weight, leaf area, leaf area index, absolute growth rate, relative growth rate, and net assimilation rate. Agronomic variables related to grain yield and the Pearson correlation between the random variables were also determined. Increasing the dose of the effluent from the biodigester septic tank reduced the performance of the variables related to growth analysis and grain yield. The 8-mm effluent dose resulted in cowpea productivity similar to that obtained with the NPK fertilizer recommended for the crop.