Weed Species Richness and Diversity in Smallholder Cereal Fields as Influenced by Soil Fertility and Cropping History

Abstract

Weed species richness and diversity in smallholder cereal-based farming systems are strongly influenced by soil fertility status and long-term cropping history. Field surveys were conducted across representative smallholder cereal fields to assess weed community composition and to evaluate the relationship between soil fertility parameters, management history, and weed diversity patterns. Weed flora was recorded using quadrat sampling, and species were analyzed using standard phytosociological indices including density, frequency, abundance, and diversity metrics. Soil samples were analyzed for key fertility indicators such as organic carbon, nitrogen, phosphorus, potassium, and pH to determine their association with weed community structure. Results indicated that fields with higher soil fertility supported greater weed species richness and overall diversity due to improved resource availability favoring both crop and weed growth. In contrast, low-fertility soils exhibited reduced species richness but were often dominated by a few highly adapted and stress-tolerant weed species. Cropping history significantly influenced weed composition, with continuously cultivated fields showing higher dominance of annual weeds adapted to frequent soil disturbance, while fields with diverse crop rotations supported more balanced weed communities. Long-term monocropping systems promoted the persistence of competitive weed species and reduced overall community evenness. Seasonal variability further contributed to fluctuations in weed emergence and population dynamics, particularly in relation to rainfall distribution and soil moisture availability. The study highlights the combined influence of soil fertility and cropping history in shaping weed community structure in smallholder cereal systems. Understanding these relationships is essential for developing site-specific weed management strategies that integrate soil health improvement and diversified cropping practices.