Endogenous honeycomb stone arrangements reduce soil erosion, improve soil moisture, and sorghum productivity under fertilizer microdosing on steep lands of Boukombé in northwestern Benin

Abstract

The biophysical field-based evaluation of the endogenous soil and water conservation (SWC) practices in the hilly region of sub-Saharan West Africa is lacking. To address this, the current study aims to evaluate the most commonly used erosion control practices in the hilly region of Boukombé through a rainfed field experiment conducted under sorghum over two growing seasons (2012–2013) on a hillside (22% slope). A split-plot design was used with two factors. The main plot includes SWC: rectangular honeycomb (RHC), circular honeycomb (CHC), and a control as ordinary contour stone rows (SR). The subplot involved four levels of mineral fertilization: recommended dose (RD; 230 kg NPK ha-1 + 50 kg Urea ha-1); microdosing option 1 (72.2% of RD); microdosing option 2 (36.1% of RD); and a control. Measurements included runoff, soil loss, soil moisture, sorghum biomass, and grain yield. The key findings revealed that CHC and RHC performed the best, reducing runoff by 25.05% and 17.65%, respectively, and decreasing soil loss by 52.01% and 38.55% compared with SR. CHC thus produced the highest soil moisture, increasing it by 8.52% to 10.52% over other structures, and induced 52.38% more biomass and 87.42% more grain yield compared to SR. Microdosing fertilization practices showed significant synergy with honeycomb stone arrangements and thus could be used in combination with honeycomb to substantially increase sorghum productivity. Circular honeycomb stone arrangements may be considered a promising SWC option for similar steep semi-arid hillsides, pending further evaluation of labor requirements, adoption constraints, economic analysis, and long-term performance.