Effects of different nitrogen fertilizers on the yield, water- and nitrogen-use efficiencies of drip-fertigated wheat and maize in the North China Plain

Fertigated areas of wheat and maize in the North China Plain (NCP) have grown rapidly during recent years, but little information is available on the effects of different nitrogen (N) fertilizers applied through drip fertigation on wheat and maize. A field experiment was conducted in the NCP during 2012-2016 to evaluate the effects of urea, ammonium nitrate, ammonium sulfate and calcium nitrate applied by drip fertigation (no N as the control, CK) on grain yield, water use efficiency (WUE), N use efficiency (NUE) and N loss in wheat and maize. A total of 250 kg N ha(-1) and 205.5 kg N ha(-1) were split into six and four applications and applied by drip fertigation at key growth stages during the wheat and maize growing seasons, respectively. The results showed that urea and calcium nitrate produced higher yields (p < 0.05) than ammonium nitrate and ammonium sulfate in the first year of the study in both wheat and maize, whereas in subsequent years, ammonium sulfate increased the yield of wheat by 11.3 %-25.1 %, 13.7 %-46.1 % and 16.4 %-32.7 % compared with urea, ammonium nitrate and calcium nitrate, respectively. Urea and ammonium sulfate averagely produced higher maize yields than ammonium nitrate and calcium nitrate, but no significant difference in maize yield was found between urea and ammonium sulfate. Similar trends in WUE and NUE were recorded in both crops. Ammonium sulfate contributed to higher WUE and NUE in wheat compared to the other N fertilizers except in the first year, while urea contributed to higher WUE and NUE in maize. The total apparent N loss in urea was 13.9 %, 15.4 % and 15.8 % lower (p < 0.05) than those in ammonium nitrate, ammonium sulfate and calcium nitrate after three cycles of the rotation (2012-2015), respectively. Considering both yield and NUE, and based on the results of apparent N loss for the four N fertilizers under field conditions, ammonium sulfate was recommended as the superior N source for wheat under drip fertigation, while urea was the optimal N source for maize under drip fertigation.

Automated summary

The study found that urea and calcium nitrate had higher yields in the first year, while ammonium sulfate increased wheat yield in subsequent years and urea and ammonium sulfate had higher average yields for maize, with urea performing better in NUE and WUE. Urea also had lower N loss compared to other fertilizers after three cycles, making it the optimal choice for maize under drip fertigation.