Determinants of Soil Additive Application by Farmers in Delta State: An Economic and Extension Perspective

Abstract

This study examines the determinants of soil additive use by farmers in Delta State, Nigeria, in the context of declining soil fertility from intensive cultivation. Using a multi stage random sampling procedure, 238 farmers were surveyed. Results show that 64.7% of respondents primarily used inorganic fertilizer; other additives reported included organic manure (12.1%), wood ash (6.8%), lime (4.5%), and other materials (8.3%); 6.1% used no additives. The main barriers to additive use were high prices (mean = 4.79), low income (mean = 4.74), and product scarcity (mean = 4.69). Cost benefit analysis indicated that users of soil additives earned an average income of N180,000 per hectare compared with N95,000 for non-users, producing net returns of N115,000 and N50,000 respectively. A binary logistic regression identified five significant determinants of soil additive use: educational level, farm size, extension contact, household size (negative effect), and monthly income. The model yielded χ2 = 226.792 (p < 0.01), a correct classification rate of 72.6%, and Nagelkerke R2 = 0.589. The evidence points to the need for strengthened farmer education, improved extension outreach, and policy measures that increase access and affordability of soil additives to support sustainable crop productivity in the region.