Effect of fertilizer rate and water irrigation quality on the recovery of 15N-labeled fertilizer applied to Sudangrass

Abstract

Wastewaters are increasingly used for irrigation of cropping systems in Tunisia. However, to develop environmentally sound practices the contribution of wastewater to crop N nutrition needs to be clarified, especially in cropping systems already receiving mineral fertilizers. For a better understanding of the interaction between fertilizer N and N originating from wastewater, experiments using 15 N were conducted. 15 N-labeled fertilizer was applied at different rates (0, 60, 100 and 140 kg N•ha-1) and with different water irrigation qualities (tap water or treated wastewater) to sorghum grown in lysimeters during 1998 and 1999. Recovery of 15 N-labeled fertilizer in the above-ground crop at final harvest in treated wastewater irrigation was higher at the lowest rate of fertilizer application (54%), with the amount recovered in the crop increasing as the rate of 15 N-labeled fertilizer application increased up to the rate of 100 kg N•ha-1. Nevertheless, in spite of this increase in 15 N-labeled fertilizer in the crop, total plant N uptake did not differ between rates. Treated wastewater irrigation had no negative effect on the recovery of 15 N-labeled fertilizer. About 62 and 55% of 15 N-labeled fertilizer was removed by Sudangrass in either tap water or treated wastewater. Neither fertilizer N rate nor water quality had an effect on the 15 N-labeled fertilizer remaining in the soil at final harvest. On average 20% in the wastewater treatment (19-24%) and 30% in the tap water treatment (26-31%) of the 15 N fertilizer applied were in the 0-60 cm layer of soil at final harvest in 1998 and 1999, respectively, and mostly present in the 0-20 cm layer. The proportion of applied 15 Nlabeled fertilizer remaining in the soil at final harvest increased with increasing N rates. About 60, 69 and 72% of 15 N left in the soil at final harvest was in the surface 0-20 cm layer. Residual 15 N was greatly higher in soil following the first harvest than after the final harvest, with the greatest value (38%) measured at the lowest rate of 15 N-labeled fertilizer (30 kg N•ha-1). Losses of 15 N-labeled fertilizer increased with application rate, but were unaffected by water quality irrigation. Approximately 13% of the applied 15 N fertilizer was lost following the application of 100 kg N•ha-1 with either treated wastewater or tap water irrigation.

Modeling of Nitrogen Use Efficiency in Lettuce Culture (Lactuca sativa): Isotopic Nitrogen (15 N) and AquaCrop

“…The NUE decreased from 74.49% to 68.38% by increasing the rate from 120 to 180 kg N/ha. These results are similar to those reported by [32,33]. The 120 kg N/ha rate provides the best efficiencies.…”

The effect of irrigation on nitrogen uptake and use efficiency of two willow (Salixspp.) biomass energy varieties

“…Within the agronomic literature, the amount of 15 Nlabelled fertilizer recovered by the target crop typically incrases with increasing rates of fertilizer N addition, with or without irrigation (Pilbeam et al 1997;Tran and Tremblay 2000;Khelil et al 2005). The absence of a fertilizer rate effect (or any interaction thereof) on the Fig.…”

Mean age distribution of inorganic soil‐nitrogen

“…The trace of nitrogen constituents in agricultural soil has been previously estimated from nitrogen isotope experiments, especially labeled 15 N compounds, particularly for estimating the efficiency of fertilizer use [ Azam et al ., ; Isfan , ; Khelil et al ., ; Rahman et al ., ; Kchaou et al ., ] and the ultimate fate of the applied fertilizer [ Bedard‐Haughn et al ., ; Jenkinson et al ., ; Stevens et al ., , ; Sebiloa et al ., ]. It was observed that the availability of nitrogen to plants from the fertilizer dependents on an interplay between the fertilizer type (such as ammonium, nitrate, and urea), crop and soil characteristics, field management, and weather.…”