Improved soil physicochemical, biological properties and net income following the application of inorganic NPK fertilizer and biochar for maize production

Abstract

A field experiment was conducted in 2019 (minor season) and 2020 (major season) to study soil properties and net income response to inorganic NPK fertilizer and biochar application for maize production. The experiment was made up of 2 × 3 factorial combinations of biochar (0 kg ha−1, 2000 kg ha−1) and inorganic NPK fertilizer (0:0:0 kg NPK ha−1, recommended rate; 90:60:60 kg N: P:K ha−1, half of recommended rate; 45:30:30 kg N:P:K ha−1). In both seasons, biochar and inorganic NPK fertilizer applied separately or in combination improved soil properties (dehydrogenase activity, CEC, organic carbon, bacterial and fungal population, microbial biomass carbon and basal respiration rates) and yield significantly. In 2019, however, mineral N and available P did not increase in biochar amended plots. Significant interaction effect was observed between biochar and NPK fertilizer application which could be related to positive soil conditioning of biochar and biochar surface charges which enhanced retention and steady release of nutrient supplied by NPK fertilizer for maize use. Maize grain yield and profit in both crop seasons increased significantly and followed an increasing order of control < sole biochar < NPK (half rate) < NPK (full rate) < combined biochar + NPK (full rate) = combined biochar + NPK (half rate). Farmers in this agro ecological zone are encouraged to apply biochar + inorganic NPK fertilizer (45:30:30) due to its low total production cost, improved maize grain yield and high net income compared to the full rate (90:60:60) or full rate + biochar.