Co-Application of Biochar and Poultry Manure Improves Rice Yield and Enhances Topsoil and Subsoil Nutrient Availability in Lowland Rice System under Minimum Tillage

Rice is an important food security crop in Ghana and Africa. Poor soil quality and fertility, due to improper management and expensive mineral fertilisers, have contributed to low annual production target. The experiment was conducted to evaluate the effect of co-application of biochar and poultry manure (BC + PM) alone or in combination with mineral fertiliser on soil nutrient dynamics, as well as their contribution to rice growth and yield. The study involved five treatments: T1, control (no fertiliser); T2, full rate of BC + PM (5 t ha−1);T3, 1/2 rate of BC + PM (2.5 t ha−1) + 1/2 rate of NPK (45:30:30 N: P2O5:K2O) kg ha−1; T4, full rate of NPK (90:60:60 N: P2O5:K2O) kg ha−1, and T5 – 1/2 rate of NPK (45:30:30 N: P2O5:K2O) kg ha−1, using a randomised complete block design (RCBD) with three replications. The findings showed improved rice growth and yield parameters with T4, T2, and T5 outperforming T3 and T1. Pre-harvest soil analysis revealed higher levels of NH4-N in T4, T5, T3, and T2, at 85%, 74%, 39%, and 37%, respectively, compared with the control. At harvest, NO3−N, NH4−N, total nitrogen (TN), and total phosphorus (TP) decreased with increasing soil depth in T2 and T3. Correlational analysis further showed a strongly significant and positive (p < 0.05, r = 0.57–0.63) relationship between AN and NH4−N with growth and yield parameters. Consequently, for enhanced and environmentally sustainable rice production, BC + PM at 5 t ha−1 is recommended, either solely or with NPK at the recommended rate.