Determine how plant age influences the effect of short-term wastewater irrigation on growth and nutrient uptake, soil available and N and P concentration. Sandy soil was left unplanted or planted with wheat and then watered with reverse osmosis (RO) water for 20 days. Wheat was planted so that plants were 7, 14 or 21 days old when half of the pots were irrigated with wastewater from days 20 to 35; the other pots received RO water until day 35. Similarly, unplanted pots received either RO or wastewater water from days 20 to 35. Irrigation with wastewater had little effect on plant dry weight, shoot N and P concentration or available N and P, and microbial biomass N and P in soil in both planted and unplanted treatments. Wastewater irrigation increased shoot N uptake compared with RO treatments only in plants that were 21 days old at the start of wastewater addition. Presence of plants reduced available nitrate up to 30-fold compared with unplanted soil. In this sandy soil, short-term wastewater irrigation had little effect on wheat growth, N and P uptake, and N and P concentration in soil. However, presence of plants reduced available N and P in soil compared with unplanted soils which would reduce potential of nutrient leaching after wastewater irrigation.

中文翻译：

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短期灌溉废水对小麦生长和土壤中氮磷的影响

确定植物年龄如何影响短期废水灌溉对生长和养分吸收、土壤可用量以及 N 和 P 浓度的影响。沙质土壤不种植或种植小麦，然后用反渗透 (RO) 水浇水 20 天。种植小麦时，在第 20 至 35 天用废水灌溉一半的盆时，使植株长 7、14 或 21 天；其他盆在第 35 天之前接受 RO 水。类似地，未种植的盆在第 20 至 35 天接受 RO 或废水。用废水灌溉对植物干重、芽 N 和 P 浓度或有效 N 和 P 以及微生物影响不大。种植和未种植处理中土壤中的生物量 N 和 P。与 RO 处理相比，废水灌溉仅在废水添加开始时 21 天的植物中增加了芽 N 吸收。与未种植的土壤相比，植物的存在将有效硝酸盐减少了 30 倍。在这种沙质土壤中，短期废水灌溉对小麦生长、氮磷吸收以及土壤中氮磷浓度的影响不大。然而，与未种植的土壤相比，植物的存在减少了土壤中的有效氮和磷，这会降低废水灌溉后养分浸出的可能性。