Tillage effects on maize yield, rooting depth and soil water content on sandy soils in Zimbabwe

Abstract

Maize ( Zea mays L.) yield from granitic soils, cultivated by different tillage techniques, were measured over a period of three rainy seasons in the subhumid and semi-arid regions of Zimbabwe. Results revealed that besides tillage, seasonal rainfall pattern and the year x site interaction had highly significant effects on maize production. In addition, topographical and soil profile characteristics were highly related to maize yields. Of five tillage systems, the no-till tied ridging technique resulted in highest grain yield in the subhumid region (4.6 to 5.0 t ha −1) but yields fluctuated strongly and were rather poor in the semi-arid zone (0.9 to 5.4 t ha −1). This was mainly due to lower topsoil water contents in the elevated ridges which prevented waterlogging in the subhumid region but caused emergence and establishment problems in the semi-arid region. In the semi-arid region, the mulch ripping technique was superior to the other treatments (2.3 to 5.9 t ha −1) in drought years if there were enough crop residues left on the soil surface from the previous season. Where this was not the case, mouldboard ploughing (1.7 to 6.5 t ha −1) and clean ripping (1.8 to 5.9 t ha −1) yielded best. Holing-out (hand hoeing), practised by subsistence farmers short of draughtpower, performed consistently well in the subhumid region (3.4 to 3.7 t ha −1), but yielded inconsistently and rather poorly compared to the other treatments in the semi-arid region (1.0 to 3.9 t ha −1).