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 (‘badlands’) 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.