Characterization and Suitability Evaluation of Soils of a Toposequence at University of Agriculture Makurdi Teaching and Research Farm for the Production of Rice (Oryza sativa) in Makurdi, Benue State

A toposequence at University of Agriculture Makurdi Teaching and Research Farm, Benue state was detail surveyed to characterize, classify and assess the suitability of the soils for sustainable rice production. Critical land and soil requirements for rice production were related with data obtained from both field and laboratory studies. The results showed that the soils had sandy loam to clay textures; weak fine crumb to strong coarse subangular blocky structure and friable to very firm consistency. All pedons except 1 had redoximorphic properties. Soil reaction ranged from slightly (6.0) to moderately acid (5.0), organic carbon (0.18-.55%). Total nitrogen and phosphorus were inadequate with low exchangeable cations and micro-nutrients. Pedon 1 was classified as Lithic Ustropept (Plinthic Cambisol (Eutric, Rhodic)) while 11 and 111 were keyed into Typic Plinthudalfs (Eutric, Plinthosols (Clayic, Greyic)). Land characteristics (mean annual rainfall, temperature, relative humidity, topography, coarse fragments and base saturation) were not major limitations for rice production however, there was no highly (S1) or moderately suitable (S2) land for rice cultivation. Productivity index (IPc) ranged between 3.10 and 10.08, and were thus currently not suitable for both upland and lowland rice cultivation by assessments of the two models. Linear model of IPp (17.55-21.06) for upland rice and (11.36) in pedon 1 for lowland rice, showed the soils were currently not suitable for rice cultivation but pedons 11 (29.25) and 111 (37.05) were marginally suitable for lowland rice cultivation. The square root model index of productivity had IPp of 21.77 in pedon 1, 26.12 in 11 and 28.37 in pedon 111. Thus, pedon 1 was currently not suitable; pedons 11 and 111 were marginally suitable for upland rice. Pedon 1 IPp (11.91) was currently not suitable whereas pedons 11 (36.79) and pedon 111 IPp (31.820) were marginally suitable for lowland rice cultivation. The soils' major limitations were the low levels of macro and micronutrients. Management techniques including continuous organic matter incorporation and mineral fertilizers application to the land will adjust the soils structure and boast their fertility level.