The effect of mulching on maize yield was investigated for luvisol and cambisol tropical soils during 1970-72. The increase in grain yield by mulching was 46, 52 and 22 per cent respectively, for 1970, 1971 and 1972. Mulched plants had higher growth rate and vigour and chlorotic symptoms of nutritional disorders were observed only for unmulched plants. Mulching significantly decreased the maximum soil temperature measured at 5, 10 and 20 cm depths. In the initial stages of crop growth, temperature differences of as much as 8°C were observed between mulched and unmnlched plots at a 5-cm depth. Mulched plots also had a higher soil moistui'e content. Increase in grain yield by mulching was attributed primarily to a decrease in soil temperature and partly to improved soil moisture regime.The sensitivity of maize to high soil temperature at the seedling stage was demonstrated by G r o b b e l a a r 7 and W a l k e r 15. During early vegetative growth the root activity of maize is confined to the upper few cm of soil and the growing point of maize remains below the soil surface until about the fourth week of growth. Though the culm development is largely embryonic, the number of ovules on the embryonic ear shoots are determined during this period of growth. Soil conditions at the early stage of growth may, therefore, determine the theoretical potential of the maize plant. The optimal range of soil temperature for maize has been found to be from 25 to 34oc s 15 Soil temperature is significantly influenced by mulching and tillage practices 1 2 s 17. Considering its agricultural importance the work done on the influence of mulches on soil and water management andAdditional key words/or indexing: soil management, cultural practices.

Rapid deterioration in soil physical properties following deforestation for arable land use adversely affects crop production from soils in the humid and subhumid tropics. This investigation was conducted to determine whether the rate of deterioration can be minimized by the use of crop residue mulches. Changes in soil properties of a newly cleared tropical Alfisol resulting from mulch rates of 0, 2, 4, 6, and 12 tons ha−1 season−1 of rice (Oryza sativa) straw were investigated from 1976 to 1977. Total porosity, 18 months after initiating the experiment, was 48, 50, 55, 55, and 59%, respectively, for increasing mulch rate. Similarly affected were relative proportions of macropores, saturated hydraulic conductivities, field infiltration rates, and moisture retention at 0.1 and 0.3 bar suctions. Decrease in the maximum temperature was 3.3, 4.1, 4.5, and 5.4°C for 2, 4, 6, and 12 ton/ha mulch rates respectively, compared with the unmulched control. The water runoff was 18, 10, 4, 1, and 0% of the rainfall received for increasing mulch rates, respectively. The chemical fertility of the soil decreased with time after forest removal. However, the rate of degradation was less with increasing mulch rate. The rate of decline of organic matter content over the 18‐month period was 0.103, 0.100, 0.092, 0.083, and 0.078% per month for 0, 2, 4, 6 and 12 tons/ha of mulch, respectively.

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