Influence of soil organic carbon, fertiliser management, and weeding regime on weed dynamics and maize productivity on sandy soils in eastern Zimbabwe

Labour bottlenecks and multiple operations at the start of a cropping season often result in inadequate early weed control and subsequent poor crop performance. Therefore, there is a need to establish management practices that provide the best opportunities for the gains associated with weeding and nutrient management across farms. We investigated the influence of soil organic carbon (SOC), fertiliser management, and weeding regimes on weed dynamics and maize productivity on smallholder farms with contrasting SOC in eastern Zimbabwe. On each site, and for two seasons, a 2 × 5 factorial experiment laid in a randomised complete block design was used. Fertiliser management was NPK or NPK + cattle manure (CM); weeding regimes were herbicide + hoe weeding, hoe weeding thrice/twice/once, or weedy check. Principal component analysis was used to evaluate weed density. The grain yield of maize increased by 13% on the sites with higher SOC. Integrating NPK + CM increased weed density and maize grain yield by 1.32 and 1.46-times, respectively, compared with NPK application only. The increased maize yield from fertiliser-managed treatments occurred only in early frequently weeded treatments. However, fertiliser application had little effect when weeding was delayed, as maize yield instead declined by 40–80%. We concluded that higher SOC increased weed density and weed biomass. Smallholder farmers are encouraged to combine herbicide application combined with hoe-weeding options for sustainable maize production.