ABSTRACT

Land suitability of Okoko Item in Bende Local Government Area of Abia State for sustainable rice (Oriza sativa (L.) and Taro (Colocasia esculenta (L.) production was conducted. Free method of soil survey was adopted. Three land suitability evaluation methods: simple limitation, storie index and square root index were adopted for the study to ascertain the most appropriate for the study. Four mapping units (OKIT I, OKIT II, OKIT III and OKIT IV) were delineated in the area. The soils of mapping units (OKIT I, OKIT II and OKIT IV) located at the upland area of the study site were deep, well drained and their textures ranged from LS – SCL, SL – SCL and SCL – C respectively whereas mapping unit OKIT III located at the lowland area was shallow to moderately deep, poorly to imperfectly drained and had a textural class range of CL – C. The bulk densities of the soils of the mapping units were less than the critical limits for root restriction and their total porosities were good. Mapping unit OKIT IV had a significantly higher bulk density with a resultant lower total porosity compared to the other mapping units. The high presence of gravels, stones and boulders in the mapping unit might have influenced the higher bulk density and lower total porosity. The soils were generally acidic, low in total nitrogen, low to medium in organic matter and moderate to high in available phosphorus. Base saturation was low in mapping units OKIT I and OKIT II but high in mapping units OKIT III and OKIT IV. The soils of the mapping units were classified as Typic Rhodudults (OKIT I), Rhodic Paleudults (OKIT II), Mollic Epiaquents (OKIT III) and Typic Plinthaqualfs (OKIT IV).  Based on simple limitation and storie index methods, 489.0 ha or 26.0% of the study area were moderately suitable (S2), 246.0 ha or 13.0% of the area were marginally suitable (S3) while 1,150 ha or 61% of the area were not suitable (N) for upland rice production. Based on square root index method, 750.0 ha or 39.7% of the study area were moderately suitable (S2), 195.0 ha or 10.4% were highly suitable (S1) while 940.0 ha or 49.9% were not suitable (N1) for upland rice (Oriza sativa (L.) production. Evaluating the land suitability of the area for taro (Colocasia esculenta (L.) production, results showed that the total study area of 1,885 ha were moderately suitable (S2) based on simple limitation method. Based on storie index method, 923.7 ha or 49.0% of the area were moderately suitable (S2) and 961.4 ha or 51.0% were highly suitable (S1). Whereas based on square root index method, 1,470 ha or 78.0% were highly suitable (S1) while 414.7 ha or 22.0% of the area were moderately suitable (S2) for taro production. Comparing the results of the three methods used, it was observed that the suitability classes assigned by square root method were superior to that of storie index and simple limitation methods. However, it was evident that the three methods were closely related, although storie index and simple limitation methods showed more correlation. Generally, the study area has minor fertility limitation which influenced the level of suitability to both crops. Hence, the suitability and productivity level can be improved with the use of integrated organo-mineral fertilizers. However, the area with drainage limitation could be used for the cultivation of hydrophytes e.g. swamp rice, vegetables.