Irrigation Suitability Ratings and Okra Productivity of Some Mid - Benue Trough Soils: a Comparative Analysis

A detailed soil survey using grid method was conducted to characterize and rate irrigation suitability of soils and relate it with okra productivity under surface irrigation. Two soil profiles were dug at each site and morphologically described. Soils sampled from identified profile horizons were analyzed. Parametric evaluation method using the soil characteristics was employed. A 4×4×4 factorial experiment was laid out in RCBD with 4 okra varieties. There were 4 irrigation frequencies and 4 locations as treatments, replicated three times. Data collected were subjected to ANOVA using GENSTAT 5 Release 4.24 with means, separated by Fishers Least Significant Difference. Mean fruit yields were used for comparative analysis. Water from adjoining rivers were sampled and analyzed. Soils ranged from shallow (50 cm) to very deep (200 cm), textures from sandy loam to clay loam surfaces with weak fine crumb to weak fine to medium crumb (DFP), granular (KRD, MRB) and coarse subangular blocky (TRF) subsurfaces. Water infiltration ranged from 0.45 to 2.40 cmhr-1, hydraulic conductivity (1.06 to 23.34 x10-4 cmsec-1) pH (5.51-6.15), EC (0.12-0.18 dsm-1), Organic carbon (0.20-1.46 %) decreased with depth. Total nitrogen followed trends in organic carbon with available phosphorus ranging from 5.00 to 9.40 mgkg-1, CEC (5.31-7.76 cmolkg-1) and CaCO3 (0 - 5 %) and were generally very low to medium. Okra varieties productivity index (Pi) did not agree with the soil irrigation suitability ratings of KRD soils. The moderately suitable (S2) class for Makurdi and Logo varieties conformed to the irrigation suitability rating of DFP soils. The highly suitable (S1) rating for NH47-4, Makurdi and Logo was in conformity with the highly suitable class of the MRB soils. The Pi (57.07 and 47.65) for Makurdi and Yandev Serial also conformed to the Si of TRF soils. Location and variety highly influenced okra fruit yields but irrigation frequency had no drastic effect on fruit yield of okra. All irrigation water parameters examined conformed to the irrigation water standard. The soils characteristics ranged from very low to low. Both the soils and water were suitable for surface (gravity) irrigation. Parametric evaluation method was therefore, effective in the study area.