Soil Productivity Assessment of Soils in Orire Local Government Area of Oyo State for Cashew Production
Detailed soil survey was carried out on 106 acres of land with the major aim of evaluating the land for sustainable and profitable cashew Production in Agbanda, Orire Local Government Area of Oyo state, Nigeria. Soil properties such as: Soil Texture, Bulk Density, pH, Organic Carbon, Nitrogen, Potassium, Available Phosphorus, Ca, Mg, Fe, CEC, and climatic data on Temperature, and Rainfall. According to the degree of favorable environment for cashew crop (FAO, 1984), simple statistical weighting/ratings were used for all the variables leading to multi-criteria decision support approach. Three rating systems, like “1” as suitable, “2” as moderately suitable and “3” as unsuitable were used to rank all the variables.
The soil pH of all the sites was slightly acidic (4.48 – 6.5). Generally, all the soil samples tested were very low in essential nutrients especially total nitrogen and available phosphorus. The organic carbon and matter in the site have been greatly depleted. The samples equally have high concentrations of extractable Fe. From the analyzed results, the land was grouped to four mapping units, indicated as RRY1 (degraded land as a result of land clearing), RRY2 (land laden with plinthite), RRY3 (soils with no major constraints) and lastly RRY4 (soil with high water table content).
RRY3 Soil mapping unit was moderately suitable for cashew production with very little amendments to enhance productivity and sustainability. Soil mapping unit RRY2 which covers about 72.36% of the whole land was rated moderately suitable, however, it will require more amendment with addition of organic manure such as compost, farm residues, animal dungs fortified with NPK, Zinc and Sulphur. Soil mapping unit RRY1 was rated unsuitable because of the high level of sesquioxide that have reached an irreversible stage making penetration of plant roots, water and nutrient impossible. Therefore, it is advised that this zone should be for other farm activities such as farm houses equipment store and warehouses. While RRY4 soil unit could be used for planting other water loving crops such as vegetables, fruits, plantain and bananas.
In conclusion, if all the percussions are taking into cognizance, about 77.89% of the total land could be used for profitable and sustainable cashew production. The remaining areas of land (22.11%) need serious soil amendment to make them suitable for cultivation of the targeted tree crops.