The Effects of Different Soil Tillage and Management Practices on the Physical and Chemical Properties of Soil and Maize Yield in a Rainforest Zone of Western Nigeria

After World War I (1914–1918) a search for a permanent form of cultivation in Nigeria began. Among the methods tried were replacement of natural fallow with leguminous covercrops, planted grass fallow, and late minimum or zero tillage. With zero tillage, weed control and fertilizer application methods are problems that need immediate attention. An experiment conducted for 4 years employed the following eight treatments: (1) no tillage, no fertilizer; (ii) no tillage, fertilizer surface applied, herbicide applied; (iii) conventional tillage, fertilizer worked into the soil with implements; (iv) no tillage, fertilizer banded with hoe; (v) conventional tillage, fertilizer banded with hoe; (vi) herbicide, fertilizer banded with hoe; (vii) herbicide, no fertilizer; and (viii) herbicide, fertilizer mixed in a groove and maize (Zea mays L.) planted in the groove (partial tillage). Post harvest soil analysis indicated that the treatments did not appreciably affect the nutrient elements in the soil except for K which recorded a 19% increase in the last year. Tillage and fertilizer application reduced the organic matter content of the soil by 19 and 33% over the 4-year period. The bulk density did not change much but tilled plots recorded slight increases with a range of 1.29 to 1.36 g/cm³. No-tilled plots retained more water than tilled plots. Treatments with fertilizer gave much greater average yields than those without fertilizer. The decline in yield was related to the level of soil organic matter, method of fertilizer application, and tillage operations. Banded fertilizer had an edge over other methods. Tillage operations constituted an important factor of yield reduction, although the effect was masked by fertilizer treatment. The herbicide effect was probably on the organic matter level but this was masked by fertilizer treatments as well. In developing a more permanent form of agriculture in the tropics, soil management practices especially under a zero-tillage system, should recognize weed control methods, and fertilizers that minimize reduction in soil organic matter and maintain high yield under continuous land use.