REDOX POTENTIAL EFFECTS ON SOIL BIO-ELECTROCHEMICAL PROPERTIES AND RICE PERFORMANCE UNDER FIELD CAPACITY AND WATERLOGGED CONDITIONS

Abstract

Redox reaction, measured by redox potential (Eh) represents the electron fluxes of a system or the presence or absence of electron in a system. This redox potential also determines the oxidation or reduction status of an environment. However, little is known about the soil redox potential, hence, this research sets out to evaluate the effect of redox potential on the biological, chemical and electrical properties of soil and rice performance under waterlogged and field capacity conditions. The experiment were sited in two farmers’ farm at “Apatapiti” area, close to FUTA in Akure South Local Government area of Ondo State.Two texturally different soils (Sandy clay loam and Clay loam) were collected and used for the pot experiment. The experiments were 3x2x2 factorial experiments laid out in Randomized Complete Block Design (RCBD) and consisted of three factors namely: Poultry manure at three levels (0 tha-1, 6 tha-1 and 8 tha-1), NPK 15-15-15 at two levels (0 kgha-1 and 200 kgha-1) and watering regimes at two levels(waterlogged and field capacity). The combination of these variables resulted in twelve (12) treatments which were replicated three times and repeated. Each experimental unit comprised of three buckets and each bucket was filled with 5kg homogenized soil. Rice (Faro 44), was used as test crop for the trial, it was first raised in the nursery before being transplanted into the bucket. Prior to transplanting, soils in the bucket were incubated for one (1) week to allow for proper interaction. Growth parameters (Plant height, number of tillers and number of leaves) and yield parameters (grain yield and 1000 grain weight) were collected from all the plants.Soil samples were also collected before and after the experiment to analyze for chemical, electrical and biological properties. Data collected were subjected to analysis of variance (ANOVA) using SPSS version 17 and means compared using Tukey Honesty Significant Difference (HSD) test to verify significant differences among treatments at 5% probability level. Graphs were generated using Microsoft excel 2010 edition.The results of this research showed that redox potential causes changes in the bio-electrochemical properties of the two soils. There was significant difference (p < 0.05) in the nitrogen content among the treatments and the highest was moderately reduced soils being 62.5% greater than the oxidized soil that recorded the lowest. There was also significant difference (p < 0.05) in the available Pwhich was highest under oxidized soils, being 76.4% greater than the highly reduced soil that recorded the lowest. Organic matter content was highest under highly reduced soil being 42.9% greater than the oxidized soil that recorded the lowest. There were also significant differences (p<0.05) among the treatments in terms of exchangeable cations, ionic mobility and strength, total dissolved solid, electrical conductivity and resistivity. Exchangeable cations were lowest in soil under highly reduced conditions. Mobility was highest under highly reduced conditions as well as ionic strength (25% greater than in the oxidized soil) and total dissolved solid (34.8% greater than in the oxidized soil). Electrical conductivity was also highest under highly reduced conditions being 25.25% greater than the oxidized which recorded the lowest while resistivity under oxidized being 26.9% greater than the highly reduced which recorded the lowest. There were also significant differences (p<0.05) among the treatments in terms of the biological properties; fungi population is optimal under oxidized to moderately reduced soil, having a greater population than in the highly reduced soil by 42.4%, while bacteria population is dependent on the oxygen requirement of the bacteria. Rice (Faro 44) agronomic performance was optimal under moderately and highly reduced conditions, hence these two condition are recommended for the cultivation of Faro 44 rice.