Dolomite, drainage, organic manure, and natural phosphate utilization to mitigate the effect of iron and sulfide toxicity on rice productivity in irrigated rice fields: case of Burkina Faso

Rice cultivation in Burkina Faso faces major constraints from iron and sulfide toxicities that reduce rice productivity. This study investigated strategies to mitigate these stresses through improved drainage, fertilization, and variety selection across seasons. Field experiments were carried out in the Kou Valley during the dry and rainy seasons using a split-split plot in a Lattice design with three replications. Two rice varieties—FKR76 (iron-susceptible) and FKR62N (iron-tolerant)—were evaluated under two drainage regimes (D0: no drainage; D2: 14-day drainage) and eight fertilization treatments, including NPK + Urea (F2), NPK + Urea + Dolomite + Zn (F3), and NPK + Urea + Natural Phosphate (F4), each with (FO) or without (SFO) organic manure. Dolomite, organic matter, and natural phosphate were applied at rates of 200 kg·ha⁻¹, 15 t·ha⁻¹, and 250 kg·ha⁻¹, respectively. Results indicated significantly higher yields during the rainy season for both varieties (p < 0.05), with FKR62N producing 2730 g·plot⁻¹ and FKR76 2115 g·plot⁻¹ under FOF3 and FOF4 treatments. In the dry season, FKR76 showed significant differences in yield (1206.87 g·plot⁻¹), tiller number (107.85), and panicle number (92.58), whereas for FKR62N, only panicle number varied significantly, for all treatments combined. Drainage improved yield and panicle formation for FKR62N but had a limited impact on FKR76. Overall, integrating tolerant rice varieties with periodic drainage and fertilization using FOF3 or FOF4 appears promising for improving yields in iron- and sulfide-toxic soils. Although FOF3 favored FKR62N and FOF4 performed better for FKR76, these effects were not fully consistent across seasons. Multi-season and multi-site studies are therefore required to validate these trends and ensure the robustness of the proposed fertilization strategies.