THE EFFECTS OF ORGANIC AND INORGANIC AMENDMENTS ON SOIL PHYSICAL-PROPERTIES AND MAIZE PRODUCTION IN A SEVERELY DEGRADED SANDY SOIL IN SOUTHERN NIGERIA

The effects of different application rates of organic and inorganic fertilizers on soil physical properties and maize production in a severely degraded Ultisol in southern Nigeria were studied for two growing seasons. The addition of poultry manure (10 t ha(-1)) significantly decreased soil bulk density (P = 0.05), increased soil organic matter content total porosity, water infiltration into the soil and hydraulic conductivity. Water retention at low tensions of between 0.1 and 0.33 bar was significantly improved (P = 0.05) and so, too, was the available-water capacity. There were high positive correlations between soil organic matter content and some measured parameters: total porosity (r = 0.93), water retained at 0.33 bar tension (r = 0.96) and available water capacity (r = 0.96). Poultry-manure application significantly improved average maize height and average maize grain yield (P = 0.05) in the two planting seasons. The soil organic matter content was highly correlated with yield (r = 0.86). Poor response in terms of yield is a pointer to the important facts that severely degraded soils ('bad-lands') of southern Nigeria not only lend themselves to high wastage of added inorganic fertilizers, but also need sizeable quantities of organic amendments - exceeding 10 t ha(-1) of poultry manure - for restoration of their productive capacities to optimum levels.