Nitrate-nitrogen and Related Nutrient Contents of Some Alluvial Vegetable Production System in Delta State, Nigeria

A study was conducted in the alluvial soils located in Oko-anala in Delta State, Nigeria. These alluvial soils are primarily used for intensive vegetable production for commercial purposes. The total land area of about 3.34 Square kilometer was divided into three consociations and composite soil samples collected from pre-determined depths of 0-15 and 16-30cm. The samples were routinely prepared, analyzed for Nitrate-Nitrogen using spectronic 70 electrophotometer method. The other nutrient contents of the soils were also measured using appropriate laboratory methods. The results of the study showed that the NitrateNitrogen (NO3-N) contents of the soils were low and ranged from 0.12-0.16 gkg. The soils pH were moderately acid to slightly alkaline 5.7-7.7, Organic carbon content were low to moderate 17.41-25.32 gkg. Total nitrogen and available phosphorous were low being lower than 1.5 gkg and 8.0 mgkg. The exchangeable cations and CEC were within low to moderate ranges, while the percentage base saturation was above 80% in all the consociations. The particle size fractions varied from loamy fine sand, to sandy clay loam. The general results showed that nitrate-nitrogen was low at the surface horizons and tend to accumulate in the lower horizons due to leaching while the other nutrients evaluated were low to moderate in concentrations depicting low to moderate fertility of the soils.