A Preliminary Survey of the Fertility Status of Soils in Ondo State under Traditional Cultivation
Surface and subsoil samples, as well as maize leaf samples were collected from local fields at about ten kilometers intervals along the major and minor highways across Ondo state in 1977. The samples were subsequently processed and analysed for various components in the laboratory. The surface 0-15cm soil samples showed a mean of 23; 7pp NO3 -N, 13.6ppm avail. P, 119.4ppm exch. K, 1168 ppm exch. Ca, 98.2 ppm exch. Mg, and Na-EDTA-extractable trace elements in the amount 131.9, 9.0, 319 and 1.3ppm of Fe. Zn, Mn, and Cu respectively. About 93% of the samples had a pH value between 5 and 7, while the soils had a mean 0.M content of 1.9% and C.E.C. of 11.4 meq/100g soil. About 77% of samples had a base saturation exceeding 50%. The values of these parameters generally decline down the soil profile to the 90cm depth studied. From the frequency distribution of various amounts of nutrients in the soil and plant tissue samples, it was concluded that N, P and Cu were generally deficient in the soils, while Ca. Mg, Fe. Mn, and Zn appeared adequate for optimum crop growth. However, it was difficult to make a definite statement, one way or the other, about K because of the seemingly contradictory conclusions that could be drawn from evaluating the soil and plant tissue data, which evaluations were based on what are generally believed to be the critical levels of K in soil 3nd maize plant for optimum crop yield. A further study to determine the internal and external critical nutrient requirements of crops in these soils is considered a priority.