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.

本研究旨在探究采用DEWATS出水进行水肥一体化灌溉对作物氮、磷吸收、养分淋失、土壤留存以及地下水污染潜在风险的影响。本研究采用随机完全区组设计（Randomised Complete Block Design, RCBD），设置3个区组与2种灌溉处理：DEWATS出水灌溉，以及自来水灌溉配施无机肥料。分别于种植前、种植后504天与992天，从0.3 m和0.6 m两个土层采集土壤样品，测定其pH值、硝态氮、铵态氮、硝态氮、全氮与有机碳含量。通过安装在0.3 m和0.5 m深度的湿润锋探测器收集淋滤液，并依据水与废水分析标准方法对其中的硝态氮、铵态氮与正磷酸盐磷含量进行测定。通过设置在试验田内外不同位置的6个1 m深测压管，监测地下水位埋深（地面至地下水位的距离）。其中测压管P1、P2位于田块上坡外侧，P3、P4、P5设置于每个区组内，P6位于田块下坡外侧。采集香蕉与芋头作物的植物组织样品，分别测定其氮、磷浓度。所收集的原始数据采用GenStat 18版（英国VSN国际公司）进行方差分析，最终报告包含均方的方差分析表，并以星号标注不同显著性水平下的差异显著性。