Nutrient uptakes and maize productivity as affected by tillage system and cover crops in a subtropical climate at Ishigaki, Okinawa, Japan

Abstract

Using mulch to tackle the problems of soil fertility depletion and weed management may contribute to improved crop productivity in most tropical and subtropical developing countries. We conducted a field study on slope plots on Ishigaki Island, Japan, to assess the effect of zero tillage and cover cropping on soil fertility, weed control and crop productivity under a legume–cereal (hairy vetch Vicia villosa Roth and maize Zea mays L., respectively) relay cropping system. The six studied treatments consisted of hairy vetch (HV) or weed fallow followed by nil or conventional tillage with or without fertilization. Weed biomass in zero tillage treatments was five-fold smaller than in the tilled plots. The release of nitrogen (N) from hairy vetch biomass contributed to the total N input in the soil–plant system and favored greater availability and uptakes of N and P by maize crop in hairy vetch treatments than in natural fallow treatments. In the present study, hairy vetch with conventional tillage system obtained the best maize production. The favorable soil environment with the “hairy vetch–zero tillage–half recommended fertilization” system induced a maize grain yield 0.60 t ha−1 higher compared with natural fallow with recommended fertilization. Although not significant, maize yield with hairy vetch followed by zero tillage and nil fertilization was 5% greater than yields scored with natural fallow + recommended fertilization. The above results suggest that hairy vetch cover cropping combined with zero tillage could offer opportunities for low external input farmers to substantially increase and sustain crop productivity; thereby contributing to the intensification of low-input farming systems.