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.