Responses of Okra and Soil Microbial Population Changes to the Application of Tithonia Manure

Yield reduction in okra production is mostly associated with cultivation of marginal lands or continuous land cultivation. Hence, the need for sustainable approach to resuscitating soil fertility through Tithonia diversifolia manure application may alter microbial population. Two soil depths [Topsoil (0-15 cm) and Subsoil (15-30 cm)], three levels of Tithonia manure applications (control, half recommended and recommended at 120 kg N/ha) and three okras varieties (Clemson spineless, LD88 and NHAe 47-4) were evaluated in completely randomized design replicated thrice. Soil bacterial and fungal colonies were higher in the topsoil compared to the subsoil and increased with increase in level of tithonia manure application under topsoil, while the inverse was observed under subsoil condition for bacteria colony-forming units and mycorrhizal spore count. Under topsoil, LD88 variety treated with recommended rate of tithonia manure had the highest biomass dry matter (79.4 g). Significantly higher leaf area (395.92 mm2) and biomass dry matter (66.89 g) were produced by NHAe 47-4 and Clemson spineless treated with recommended rate of tithonia manure compared to their respective controls (181.37 mm2 and 29.63 g) under subsoil. Varieties LD88 and Clemson spineless combined with recommended rates of tithonia manure were suggested for topsoil and subsoil conditions, respectively.