Quantifying nutrient deposition and yield levels of maize (Zea mays) under Faidherbia albida agroforestry system in Zambia

Inherently low soil fertility and costly chemical fertilizers contribute to low maize yield and food insecurity among rural smallholder farmers in sub-Saharan Africa. The use of fertilizer trees such as Faidherbia albida (Faidherbia) to improve the soil fertility and yield of maize is recognized by many as a good practice. This study examined the litterfall pattern, quantity, and nutrient deposition from 8-, 15- and 22-year old Faidherbia trees at two locations in Zambia before and during the 2014/15 and 2015/16 rainy seasons. Litterfall including its nutrient content was estimated using nylon mesh litter traps erected under three randomly selected representative Faidherbia trees of each age. Further, we assessed the yield levels of maize grown under 8-, 15- and 22-year old Faidherbia trees. All trees started dropping litter before the onset of the rains in both seasons. The leaf litterfall averages of the two seasons were 1.6, 1.7 and 3.8 t DM ha−1 from 8-, 15- and 22-year-old trees, respectively. These litterfall quantities translate to potential carbon and nutrient deposition of 0.7-1.6 t C ha−1, 34-83 kg N ha−1, 1.8-4.3 kg P ha−1 and 10-26 kg K ha−1 per year. The yield levels of maize for the two growing seasons under Faidherbia tree canopy were 7-12 times higher than from outside the canopy, and these yield differences were much more pronounced in the driest year (2015/16 growing season). The large nutrient deposition through litterfall and increase in maize yield under Faidherbia tree canopies show the potential of these trees to contribute to food security and mitigate the risk of crop failure on resource-poor smallholder farmers' fields, especially in drought years.