Effects of value-added urea on wheat yield and N use efficiency and the distribution of residual N in soil profiles

In this study, three kinds of value-added urea containing a certain ratio of: alginic acid, humic aicd (HAU) and glutamic acid (GU), were prepared with isotope15N urea using the urea melt technology. Pot experiments were conducted under the same N application rate (N 0.1 g/kg dry soil by the soil weight of 0-30 cm soil layer) to investigate the effects of value-added urea on wheat yields, N use efficiencies and the distributions of fertilizer N in soil profiles. The results show that: 1) Compared with urea (U), the grain yield of wheat applied with alginic acid urea (AU), humic acid urea (HAU) and glutamic acid urea (GU) are increased by 7.12%, 13.63% and 3.65% respectively. 2) The percentage of fertilizer N contribution in the total wheat N uptake ranges from 44.8%-48.0%, the percentages with AU, HAU and GU are 4.83%, 7.41% and 3.12% significantly higher than that with U. 3) The residual fertilizer N is mainly centralized in 0-50 cm soil layer with all the treatments, but the residual amounts from U treatment is significantly higher than those from AU and HAU treatments in 50-90 cm soil layer. 4) The percentages of fertilizer N apparent recoveries from AU, HAU and GU are 6.38, 15.63 and 3.08 higher than that of the U treatment. The 15N recoveries of HAU and AU are significantly higher than that of the U treatment with increased percentage points of 3.70 and 2.41, respectively. As a result, the fertilizer nitrogen loss rates of AU, HAU and GU are significantly lower than that of the U treatment with decrease of 7.64, 9.52 and 2.19 percentage points, respectively.