Combined Effect of Morocco Rock Phosphate and Chemical Fertilizer in Low-Land Rice Production in Guinea Savanna Zone of Côte D’ivoire: Replenishment of Degraded Fluvisol for Boosting Rice Production

Conventional Fertilizer Practice (CFP) has degraded the soil in lowland inducing acidification and yield decreasing (50-75%) after long term continues rice cropping. Phosphorus (P) application was suspected as main remediation factor. Therefore, the effect of rock phosphate from Morocco (RPM) was tested on rice (WITA 9) yield (RGY) with combination to Super Triple Phosphate (STP). Lowest yields (2.51-2.55 t/ha) were observed for T0a (Blank control) and 20% RPM. Moderate yields (3.32 -3.69 t/ha) were induced by T0c (CFP), 80% RPM and 100% RPM. The last and highest level of RGY range from 4.21 up to 4.26 under the effects of 90% RPM (4.21 t/ha), 60% RPM (4.24 t/ha) and 100%STP (4.25 t/ha). No significant effect of season was observed contrasting with cropping management effect. Almost the RPM rations induced greater rice grain yield (> 100%) than the blank control treatment (T0a): significant positive yield differences as yield gaps were observed in a range of 29% to 81%. In turn, only T3 (113.11%) and T5 (113.22%) induced significantly a similar effect referring to the yield of CFP (T0) and the grain yield was reduced about 13%. Using RPM in low-land rice production on Fluvisol look likes environment friendly agricultural input characterized by yield increasing over cropping cycles with residual effect up to 180%. The combination of 60% RPM to 40% STP applied once induced similar yield of 4.24 t/ha close to that of 100% STP which must be applied each cropping cycle. Therefore, the application of 60% RPM is recommended for improving low-land rice production on Fluvisol.