施用磷肥对紫花苜蓿营养价值和氮磷利用效率的影响

为探究施磷对紫花苜蓿增产效应、营养价值及氮、磷利用率的影响,探明施磷对紫花苜蓿蛋白质合成、积累影响的原因,选用品种甘农3号,在田间小区条件下优化氮肥基础上研究了不同磷素水平(P₀:0 kg·hm^-2;P₁:126 kg·hm^-2;P₂:252 kg·hm^-2)对紫花苜蓿生产性能、营养价值、氮、磷利用率及氮代谢关键酶的影响。结果表明,在适宜的氮肥施用量的基础上,126 kg·hm^-2处理紫花苜蓿年总产量最高,为33312.3 kg·hm^-2,显著高于0和252 kg·hm^-2处理(P<0.05),126和252 kg·hm^-2处理的硝酸还原酶(NR)和谷氨酰胺合成酶(GS)活性、粗蛋白含量和总蛋白产出量、氮素吸收效率和氮素生产效率均显著高于0 kg·hm^-2处理(P<0.05),且各指标均在126 kg·hm^-2处理达最大值,252 kg·hm^-2处理反而下降,说明对紫花苜蓿施用磷肥可显著增产,提升品质及提高N、P利用率;磷肥的施用量在紫花苜蓿的产量、品质和利用率的角度均表现为报酬递减规律,说明在紫花苜蓿的生产中磷肥的施用量存在阈值。在施磷水平中表现最优的是126 kg·hm^-2。适宜的磷素主要通过激发 NR和GS活性,加强自身的氮代谢能力促进对氮素的吸收和同化,从而提高紫花苜蓿产量、品质及氮素利用效率。

Effect of phosphate fertilizer application on alfalfa yield,nutritive value and N and P use efficiency

In order to investigate how phosphorus application affects the yield,nutrient value and nitrogen (N) and phosphorus (P) utilization of alfalfa,the effects of different phosphorus levels (P0:0 kg · ha-1;p1 ∶ 126 kg · ha-1;P2 ∶ 252 kg · ha-1) on the performance,nutrient value,nitrogen and phosphorus utilization and key enzymes of nitrogen metabolism in alfalfa were studied,to examine the optimal nitrogen fertilizer rate under field conditions.The variety Gannong No.3 was used as experimental material.With optimal N supply,alfalfa total annual yield under P1 was 33312 kg dry matter · ha 1,significantly higher than in P0 or P2.Activities of nitrate reductase (NR) and glutamine synthetase (GS),crude protein content,total protein yield,nitrogen uptake efficiency and nitrogen production of alfalfa were all significantly higher under P1 and P2 than under P0.Although often not differing significantly,values for all the above indexes were numerically higher in the P1 treatment than under P2.The results show that application of phosphate fertilizer to alfalfa significantly increases productivity,and improves forage quality,and N and P utilization.The application rate of P fertilizer followed the law of diminishing returns in terms of the yield,forage quality and utilization rate.In conclusion,the best P supply level was 126 kg · ha-1 in this test.The appropriate phosphorus supply enhances plant metabolic activity by promoting the absorption and assimilation of N through the activation of NR and GS activity,thereby enhancing yield,quality and nitrogen use efficiency in alfalfa.