Nitrogen and phosphorus in plant tissue, soil, leachates and water table in DEWATS effluent fertigated soil.

The aim of the study was to determine the impacts of fertigation with DEWATS effluent on N and P uptake by crops, leaching, retention in soils and potential for ground water contamination. The study was conducted in randomised complete block design (RCBD) with three blocks and two irrigation treatments (DEWATS effluent vs tap water irrigation + inorganic fertiliser). Soil data (pH, nitrate N, ammoinum N, nitrate N, total N and organic C) was collected from two depths (0.3 and 0.6 m) before planting, 504 and 992 days after planting. The leachates were collected from wetting front detectors installed at 0.3 and 0.5 m depths. These were analysed for nitrate N, ammonium N and orthophosphate P following standard methods for water and wastewater analysis. The water table levels (distance from the ground level to water table level) was monitored from six piezometers (1 m deep) installed at different locations within and outside the experimental field. The peizometers (P1 and P2) were located upslope outside the field. The three (P3, P4 and P5) were within each block and P6 was located downslope outside the field. Plant tissue samples were collected from banana and taro crop and analysed from nitrogen and phosphorus concentrations respectively. Raw data gathered underwent analysis of variance using GenStat 18th edition (VSN international, UK). The analysis of variance table showing mean squares were therefore reported. Significant differences at different levels were presented with asterisks.