Effects of residue management on arthropods populations under conservation agriculture

Maize (Zea mays L.) production in South Africa by smallholder farmers is primarily hampered by several factors, including institutional constraints, soil degradation, low input production, and insect pest attacks. Conservation agriculture (CA) is perceived as an approach that can help arrest or reverse the processes of soil degradation, improve soil fertility, pest management, and promote water conservation. However, results on the role of CA in pest management are contradictory. They show spatial and temporal variations due to the agroecosystem’s complex interactions among biotic and abiotic components. This study employed the approach of the component omission to investigate the probable effects of crop residue management on insect pest populations in a maize-based cropping system. Field experiments were carried out at ongoing CA trials at the University of Fort Hare farm (UFH) (32o 47′ S and 27o 50′ E) and Pandulwazi High School (32o 39′ S and 26o 55′ E). The trial was set up in a splitsplit plot design with 16 treatments and 3 replicates. Main plots were allocated to two tillage levels, which were split into four different crop rotation levels as sub-plot treatments. The sub-sub plots were allocated to two residue management levels. For conventional tillage study, two levels of crop rotation and residue management were considered as the different CA adoption levels by smallholder farmers. The results revealed that crop rotation and residue management influence arthropod abundances, diversity, richness, and evenness, which can be used to predict or monitor pest outbreaks. However, the synergistic influence of environmental/climatic regimes cannot be separated from the individual agronomic practices. Furthermore, pest indices cannot be independently used to predict insect pest infestation and possible outbreaks; instead, they are dependent. Hence, they are site and time specific.