TILLAGE EFFECTS ON SOIL QUALITY OF AN ALFISOL IN SOUTH WESTERN NIGERIA

Abstract

A Crop and soil management decisions may produce either detrimental or beneficial effects on soil quality. Experiments were conducted between 2001 and 2004 with the aim of quantifying the effects of tillage on soil quality. An hectare of land at the I A R & T, Moor Plantation, Ibadan. in south western, Nigeria. that had been left to bush regrowth for about 35 years was opened up for the study. The experiment was sited on an Alfisol (Iwo series). Two contrasting tillage (minimum-till and plough-till) systems were imposed. The treatments, in four replicates, were laid out in a randomized complete block design with maize (Zea mays L. var. suwan-I-YR) planted as a test crop. Data on soil quality indicators and grain yields were taken during the period of four years of cropping. Soil quality was assessed using Soil Management Assessment Framework (SMAF). The results showed that the ratings of soil quality increased from 70.2% in year 1 to 73.5% in year 2 under minim-till system. Thereafter. the quality decreased from year 2 to 63.8% in year 4. However, soil quality ratings of plough-till reduced from 65.1% in year 1 to 51 9% in year 4. The overall quality changes over the period of four years were -3.0% in minimum- till and -6.7% in plough-till plots. The negative changes in soil quality imply that there was soil quality degradation under the two tillage systems which w-ere also reflected in the grain yields obtained for the period. The beneficial effect of plough-till plots in producing the highest grain yield in year 1 was curtailed as a result of soil compaction and structural degradation in year 2 and thereafter. Although there were no significant differences in most of the soil quality indicators between the two tillage systems the negative impact of tillage was more pronounced under plough-till than minimum-till system.