The physical environment of two semi-arid tropical soils with partial surface mulch cover

Abstract

The seedbed microenvironment in soils with partial surface mulch cover will be affected by the width of the bare row zones. In this paper we compare seedbed conditions under four bare row widths [0 cm (completely mulched), 5 cm, 15 cm and completely bare] during a drying cycle in a loamy sand and clay loam soil in a semi-arid, tropical environment. It is shown that for both soils the rates of drying were greatest in the bare soil and least in the mulched soil, with the 5 and 15 cm bare row width treatments showing trends which were intermediate between the two extremes. Although soil surface temperatures were not noticeably different between the two soils, differences at depth became substantial as the soils dried, with the maximum temperature at 5 cm depth in the loamy sand exceeding that in the clay loam. There was also a steepening in the temperature gradient with depth as the soils dried. Under both wet and dry conditions, maximum temperature at 5 cm depth increased significantly with bare row width up to a width of about 25 cm which, for mulch of negligible height, approximates a bare soil. Results of this work demonstrate the benefits of maximizing surface mulch cover in the semi-arid tropics.