Ridge formation with strip tillage alleviates excess moisture stress for drought-tolerant crops

The impact of climate change is expected to be more severe in semi-arid and arid ecosystems. Seasonal and high-rainfall floods have recently become a common occurrence in semi-arid sub-Saharan countries in southwestern Africa, where ridging is becoming an important method to alleviate flooding stress in drought-tolerant crops. The objective of this study was to propose a feasible tillage method and compare its agronomical effects to those of conventional tillage practices in northern Namibia in sub-Saharan Africa. Pearl millet and cowpea were grown in the field using different tillage methods in seasonal wetlands in this area. We investigated crop yield, growth parameters, soil moisture content, and the shape of the ridge. Soil tillage using a newly proposed disc ridger for two-wheel tractors resulted in higher yield and growth rate in both crops than using the other tillage methods i.e. single mouldboard ploughing with animals and/or disc harrowing with four-wheel tractor. Ridge formation with strip tillage (partial pulverization) using the disc ridger resulted in significantly lower soil moisture content after irrigation because of the higher aspect ratio of the ridge. It is likely that large undisturbed portion remained therewith prevented the ridge from collapsing because of the irrigation water that imitated natural rainfall in this region. Therefore, ridge formation with strip tillage leads to good drainage, and as a result, proper drying of soil prevents flooding stresses thus enhancing early growth and yield of pearl millet and cowpea.