Forage and maize yields in mixed crop-livestock farming systems Enhancing forage and maize yields in mixed crop-livestock systems under conservation agriculture in sub-humid Zimbabwe

In mixed crop-livestock farming systems, smallholder farmers face the challenge of insufficient dry season livestock feed whilst crop production is mainly constrained by poor soil fertility and erratic rains. Conservation agriculture (CA) which is premised on three main principles namely minimal soil disturbance, crop rotations and mulching is being promoted as a potential solution to declining soil productivity. However, farmers implementing CA in mixed crop-livestock systems are conflicted by the use of crop residues either as livestock feed or as mulch under crop production. A study was carried from 2012/13 to 2014/15 season in Murehwa, a subhumid region of Zimbabwe, to evaluate the effects of maize-legume cropping systems on forage, maize grain yield and gross margins. In this context, forage refers to the plant material/biomass harvested for livestock feeding. The cropping systems involved one conventional tillage practice with continuous sole maize (CT), four CA treatments consisting of continuous sole maize, maize-mucuna intercrop, maize-cowpea intercrop and maize-groundnut/soybean rotations. The experiment was replicated on eight farmers' fields with each farmer treated as a replicate. Maize-mucuna (4 134 kg ha(-1)) and maize-cowpea (3 999 kg ha(-1)) intercrop systems significantly increased forage yield compared to CA sole maize (3 646 kg ha(-1)) and CT sole maize (3 076 kg ha(-1)). Among the rotations, maize-soybean rotation system performed better than the maize-groundnut system with respect to forage yield and maize grain. Intercropping and sole cropping systems however showed no significant maize grain yield difference. The highest and lowest gross margins/ha were obtained from the maize-mucuna intercrop (US$1395) and maize-soybean rotation system (US$507), respectively. The study thus suggests that farmers can grow legumes as intercrops with maize without any loss in maize grain yield. Maize-mucuna intercropping was the best of the tested cropping systems with respect to forage yield and gross margins in mixed crop-livestock systems of Murehwa.