Using biochar and poultry manure to improve the fertility of a highly weathered tropical soil and yield of lettuce

Abstract

The study was undertaken to evaluate the effects of biochar and poultry manure in improving the fertility of a strongly weathered soil and the yield of lettuce. In two separate experiments, three rates (0, 39 and 65 t ha-1 per 1 kg soil) of biochar (CCB, CHB and PMB) solely or in combination with poultry manure (0 and 10 t ha-1) were incorporated into pots containing 1 kg soil and arranged in completely randomized design. Biochar and or manure effects on SOC, mineral N, AVP, pH, ECEC, MBC, MBN and MBP were evaluated on days (3, 7, 14 28 and 42) and P solubilizing fungi (PSF) and bacteria (PSB) on day 42. All amendments significantly (P < 0.05) increased SOC, pH, ECEC, MBC, MBN and MBP for all sampling periods and PSF and PSB on day 42. Unlike PMB, CCB and CHB amended soils showed no significant differences in mineral N compared with the control by day 42. Available P in CHB and PMB amended soil showed significant (P < 0.05) increase at both rates but only significant (P < 0.05) at 65 t ha-1 for CCB treatments. In experiment three, significant increase in yield and shoot NPK were realized from PMB amended soils but insignificant in CCB and CHB treatments. In all, biochar combined with manure was superior in increasing the concentrations of SOC, NH4+-N, NO3--N, AVP, pH, ECEC, MBC, MBN MBP, PSF, PSB, shoot NPK and yield of lettuce. In experiment two, ten earthworms were exposed to CCB, CHB and PMB at respective rates of 0, 13, 26, 39, 52, 65, 78, 91, 104, 117, 130, 143 and 156 t ha-1. Significantly inverse relationship was found between biochar rates and earthworm survival. It is therefore recommended that combined biochar and manure is adopted for effective restoration of the fertility of strongly weathered soils in Ghana for lettuce production.