Effect of Rice Husk Ash and Phosphorus on Some Properties of Acid Sands and Yield of Okra

Abstract

Investigations were conducted to determine the effects of rice husk ash (RHA) and phosphorus (P) on soil pH, cation exchange capacity, base saturation, growth, and yield of okra [Abelmoschus esculentus (L) Moench]. The experiment was a 5×3×3 factorial in randomized complete block design. The soil used for the experiment was a Typic Paleudult within the “Acid Sand” soils of Calabar. Elemental analysis of RHA and fresh rice husk are also presented in this article. The results showed that organic carbon (OC) and total nitrogen (TN) were lower in the ash than in the fresh Rice Husk (RH) samples. The combination of 20 t RHA ha−1 and 40 kg P ha−1 gave the best yields of 4.80 t ha−1 fresh fruits compared to 2.69 t ha−1 in the control. Soil pH increased from 4.4 to 5.8 and from 4.9 to 6.0 in the pot and field experiments, respectively, at the optimum level (i.e., 20 t RHA ha−1, 40 kg P ha−1, and 50 kg N ha−1). The 50 kg N ha−1 was applied to all treatments to avoid N deficiency. The trends, however, followed a strong positive linear correlation. Increases in exchangeable magnesium (Mg), potassium (K), and effective cation exchange capacity (ECEC) were observed in the soil. A mean neutralizing value as low as 1.62% (calcium carbonate equivalent) and 19.35 g kg−1 OC, inherent in the RHA, was found to be responsible for ameliorating the soil acidity and thus, improving fertility of the acid sands. The RHA had no effect on the already adequate soil available P especially at high levels (RHA >20 t ha−1). In conclusion, because RHA could amend the soil acidity and keep the soil more fertile with increase in available nutrients and maintain optimum pH, it is recommended for trial as an invaluable, environmentally friendly, cheap and low‐input material for improvement of fertility of the “Acid Sands” of southeastern Nigeria.