TILLAGE AND MULCHING EFFECTS ON MAIZE YIELD FOR 17 CONSECUTIVE SEASONS ON A TROPICAL ALFISOL

Long-term field experiments were established on a tropical Alfisol at the research farm of the International Institute of Tropical Agriculture (IITA) to evaluate effects of two tillage, mulch, and fertilizer treatments on maize (Zea mays L.) yield. Two crops of maize were grown every year, from late March to late July, and from September to December. Trends in maize yields are presented for the 17 crops grown from 1979 through 1987. Average maize grain yield was 2.69 Mg/ha with no-till and 2.23 Mg/ha with plow-till during the first growing season, and 0.88 Mg/ha with no-till and 0.74 Mg/ha with plow-till for the second growing season. Application of residue mulch increased average yield from 2.33 Mg/ha to 2.59 Mg/ha during the first growing season, and from 0.69 Mg/ha to 0.79 Mg/ha during the second growing season. Application of fertilizer increased maize yield from 1.90 Mg/ha to 3.03 Mg/ha during the first growing season, and from 0.65 Mg/ha to 0.98 Mg/ha during the second growing season. In contrast with grain yields, stover yield was greater with the plow-till than the no-till system during the first growing season, hut not in the second. Stover yield increased significantly with mulch and fertilizer application. Maize grain yield was sustained with mulch and fertilizer in no-till system, which was more effective with fertilizer and residue mulch than without. Mulch application increased grain and stover yields only when fertilizer was applied. These results have application for Alfisols in the sub-humid regions of western Africa with a bimodal rainfall pattern and with a total annual rainfall of about 1200 mm to 1500 mm. The data presented support the conclusion that satisfactory maize yields with continuous and intensive cropping are possible with use of chemical fertilizers, residue mulch, and a no-till system during the first growing season. Cowpea (Vigna unguiculata) or another short-season crop may be more appropriate than maize during the second season, Since these experiments were done with manual operations, the results are applicable to small-size and unmechanized farms. With mechanized farm operations, soil compaction may become a severe problem, especially with no-till farming.