Effects of nitrogen forms on nitrogen accumulation and utilization of alfalfa in different stubbles

To study the effects of nitrogen forms on nitrogen accumulation and utilization of alfalfa in different stubbles, this study adopted a completely random design with the following treatments: a control (no nitrogen application), a single application of nitrate nitrogen, a single application of ammonium nitrogen, and a 1 ꞉ 1 mixed fertilization of nitrate nitrogen and ammonium nitrogen. Various application methods of different forms of nitrogen fertilizer on alfalfa production were also examined. The results showed that the soil nitrate nitrogen content of each treatment was significantly higher than that of the control (P < 0.05). With increasing stubbles, the soil nitrate nitrogen content of the mixed nitrogen application was the highest. The soil ammonium nitrogen content did not change significantly under different treatments and stubbles (P > 0.05). The nitrogen accumulation, nitrogen absorption efficiency, and nitrogen utilization efficiency of alfalfa in the mixed nitrogen and single nitrate nitrogen applications were significantly higher than those of the single ammonium nitrogen application treatment during the first growing year (P < 0.05) and reached a peak in the second stubble. Therefore, single applications of nitrate nitrogen and mixed nitrogen are more conducive to increasing the yield of alfalfa and enhancing its absorption, utilization, and accumulation of nitrogen. As the number of stubbles increased, the dependence of alfalfa on nitrogen increased, and nitrate nitrogen or mixed nitrogen must be added as fertilizer to ensure its yield and quality after the second stubble, thereby improving feed quality.