Role of cover crops in enhancing soil biodiversity and suppressing weeds in maize fields

Abstract:

Imagine a maize field in Colombia’s Cauca Valley where, between harvest and the next planting, the bare soil bakes under equatorial sun, losing moisture and inviting aggressive weed flushes. Now picture that same field covered by a dense mat of velvet bean that suppresses weeds, feeds the soil microbial community, and adds nitrogen—all without a single herbicide application. This research tested four cover crop treatments—Mucuna pruriens (velvet bean), Crotalaria juncea (sunn hemp), Canavalia ensiformis (jack bean), and a vetch-rye mixture—against a bare fallow control for their effects on weed suppression and soil biological activity in a maize rotation at the Universidad Agrícola del Pacífico, Cali, during the 2023 cropping year. A randomized complete block design with four replications was used. The vetch-rye mix and velvet bean reduced weed density by 73.1% and 70.0%, respectively, compared to bare fallow. Microbial biomass carbon more than doubled under these two treatments (9.12 and 8.74 × 10² μg g⁻¹ vs 4.38 in fallow). Earthworm populations increased by 58-76%. Subsequent maize grain yield was 12.4% higher following velvet bean than following bare fallow. These results confirm that cover crops can serve as effective biological weed management and soil health tools in tropical maize systems.