Effect of different activators on the compositing of threshed palm fruit bunches
This study was undertaken to investigate the composting characteristics of threshed palm fruit bunch with different concentrations of poultry droppings, cow dung and Gliricidia sepium (Jacq.) as activators with the aim of generating quality soil conditioner. Seven treatment piles of threshed palm fruit bunch comprising of threshed palm fruit bunch mixed with poultry dropping (1:1) (TPFB-P1), threshed palm fruit bunch mixed with poultry droppings (2:1) (TPFB-P2), threshed palm fruit bunch mixed with poultry dropping and Gliricidia sepium (2:1:1) (TPFB-PG), threshed palm fruit bunch mixed with cow dung (1:1) (TPFB-C1), threshed palm fruit bunch mixed with cow dung (2:1) (TPFB-C2), threshed palm fruit bunch mixed with cow dung and Gliricidia sepium (2:1:1) (TPFB-CG), and threshed palm fruit bunch alone (TPFB-CON), were set up for this study. During composting, several parameters including total bacteria and fungi count, the physicochemical properties [pH, temperature and elemental (N, P, K, Mg, Mn, Cu)], maturity and phytotoxicity index of each composting pile were measured using standard procedures. The bacterial populations of the treatment piles were between 5 x 104 cfu/g and 2 x 108 cfu/g while the fungi populations were between 5 x 103 cfu/g and 9 x 106 cfu/g. There was diversity in occurrence of microbial populations of the various piles. TPFB-P1 attained the highest bacteria counts (2 x 108 cfu/g) jointly followed by TPFB-C1, TPFB-PG and TPFB-CG with bacterial counts of 1 x 108 cfu/g. TPFB-C1 attained the highest fungi count of 9 x 106 cfu/g. The control pile attained the least bacterial (2 x 107 cfu/g) and fungal counts (5 x 105 cfu/g). The temperature regime of all the composting piles ranged between 27 °C and 43 °C. TPFB-PG attained the highest temperature (43 °C). Maximum temperatures of 41 °C, 39 °C, 38 °C, 37 °C, 35 °C and 35 °C were attained by TPFB-CG, TPFB-P1, TPFB-C1, TPFB-P2, TPFB-C2 and TPFB-CON respectively. All the treatment piles showed an alkaline pH range of 7.62 and 8.26 after composting. There was significance decrease of C/N ratio at the end of composting in all the composting piles with the lowest C/N ratio of 11.1 being observed in TPFB-P1 followed by TPFB-PG with C/N ratio of 13.6, while the highest C/N ratio of 28.9 was observed in TPFB-CON. TPFB-C1, TPFB-CG, TPFB-P2 and TPFB-C2 had C/N ratios of 13.8, 14.5, 14.6 and 19.8 respectively. The cured composts contained considerable varying amounts of elemental nutrients and very low levels of heavy metals. The phytotoxic evaluation of the various composts measured as germination index (GI) showed that all the composting piles have GI value greater than 60% which was indicative of their being none phytotoxic and suitable as soil conditioners. Except for TPFB-CON with CO2 evolution of 39.6, the respiration test of the composts had CO2 evolution that ranged between 17.4 and 32.1. All the generated composts significantly increased the growth of maize plant agronomically. In conclusion, this study established that threshed palm fruit bunches could be converted into a very good organic fertilizer especially by composting them with the right proportions of poultry droppings, cow dung and Gliricidia sepium.