Neem leaf mulch for integrated management of soil fertility, Fall Armyworm and weed control for maize production in Nigeria

Abstract

Maize (Zea mays L.) production in sub-Saharan Africa (SSA) is constrained by many biophysical phenomena, particularly declining soil fertility, insect pests, and weed pressure. This study evaluated the integrative effects of neem (Azadirachta indica) leaf mulch (NLM) on soil fertility, fall armyworm (FAW) damage and weed suppression, for maize production in the tropical Rainforest Zone of Nigeria. A field experiment was conducted at the University of Benin Teaching and Research Farm, using four mulch rates (0, 1, 3 and 5 kg m-2) arranged in a randomised complete block design, with four replicates. Fresh green Neem leaves were applied as surface mulch at sowing, 2 and 4 weeks after sowing (WAS). Results showed that NLM significantly improved soil organic carbon (27.1 to 103.5%), total nitrogen (10.5 to 33.3%), and available phosphorus (36.5 to 79.2%), relative to the control; while potassium response was minimal and variable. FAW damage was significantly reduced from 6 WAS onwards, with severity declining by more than 60% under mulched treatments. Weed density and biomass decreased substantially by 32.7 - 76.1% and 28.7 - 74.9%, respectively, with increasing mulch rates. Grain yield also increased significantly from 1.17 t ha-1 in the control to 4.13 t ha-1 at 5 kg m-2; representing up to 252.8% improvement. Yield was negatively correlated with FAW damage and weed biomass; but positively associated with yield components. The study demonstrates that neem leaf mulch is an effective option for integrated management of soil fertility, FAW, and weeds in maize production. The 3 kg m-2 rate provided a near optimal balance between performance and resource use. Further studies should assess long-term impacts and scalability of the innovation across agro-ecological zones.