Weed Suppression and Component Crops Response in Maize/Pumpkin Intercropping Systems in Zimbabwe

Intercropping is a common practice in the smallholder sector of Zimbabwe with potential contribution to weed management. The proper combination of plant population, composition of the component species and frequency of weeding which lead to weed suppression are still unknown and that prompted this investigation. The experiment was set up as a factorial experiment in a randomised complete block design with three factors- cropping systems (sole maize, sole pumpkins and maize/pumpkin intercrop), weeding regimes (weeding at 3 weeks after planting (WAP) and at 3 and 8 WAP) and pumpkin population (16.5% and 33%) of maize population. Results showed no significant effect of cropping system, pumpkin population and weeding regime on maize yield, pumpkin yield, pumpkin leaf number and weed density. Weed biomass was significantly higher (P=0.000) at weeding regimes of 3 WAP than at 3 and 8 WAP. Pumpkin population of 16.5% had higher weed biomass compared to 33%. Themaize/pumpkin intercrop had significantly (P=0.002) lower weed biomass compared to sole crops. There were significant interactions of weeding regime and pumpkin population and cropping system and pumpkin population (P=0.035). The results indicate that intercrops with 33% pumpkin population and weeded at 3 and 8 WAP are superior in terms of weed biomass suppression. Intercropping done at correct crop combination and weeding at the right time therefore shifts crop-weed competition in favour of the crop as it reduces dry matter accumulation of the weeds without affecting yield of component crops. Intercropping can therefore be used as a component in integrated weed management in the smallholder sector.