Biomass contribution and nutrient recycling of organic matter management practices in tropical smallholder annual farming systems

Integrating a combination of organic matter management (OMM) practices can increase soil fertility, biomass, and nutrient recycling, but evidence of this potential is limited. This study tested the impact of integrating a combination of OMM practices on soil fertility, biomass, and nutrient recycling on smallholder farms. Following a randomised complete block design, a four-season experiment was conducted in 2018-2019 on 10 farms. The treatments (T) included T1: cowpea-maize-bean-maize rotation; T2: cowpea-maize-bean-maize rotation + farmyard manure; T3: Faidherbia albida alleys + cowpea-maize-bean-maize rotation; T4: F. albida alleys + cowpea-maize-bean-maize rotation + farmyard manure; and T5 (control): maize monocrop with diammonium phosphate application at 50 kg/ha application rate. T1-T4 are the OMM practices. The maize in T2-T4 was undersown with Mucuna pruriens. Soil fertility parameters (i.e. pH, water holding capacity, nitrogen, phosphorus, and potassium), biomass, and nutrients in the biomass were determined. There were no differences in soil fertility parameters among all treatments (P > 0.05). From the second to the fourth season, biomass was consistently higher under T3 and T4 than in other treatments. Moreover, the nutrients in biomass were higher in T3 and T4 than in other treatments, an indicator that OMM practices with alley crops can increase nutrient recycling.