氮素添加对中国苜蓿产量与品质效应的Meta分析

氮素在苜蓿产量累积与品质提升中发挥着重要作用，但其不合理添加不仅会造成资源浪费，还会加剧环境污染，且其添加效应因试验区域、添加模式和种植管理等因素不同存在较大差异。本研究通过整合已发表的相关田间试验数据，利用Meta分析方法定量研究了氮素添加对苜蓿产量与品质（粗蛋白含量、酸性和中性洗涤纤维含量）的效应及主要影响因素。结果表明，与不添加氮素相比，添加氮素可显著提高苜蓿产量与品质，其中产量和粗蛋白含量分别平均提高12.6%（置信区间9.0%~16.2%）和7.3%（置信区间4.1%~10.6%），酸性和中性洗涤纤维含量分别平均降低5.6%（置信区间3.5%~7.8%）和3.0%（置信区间1.0%~4.9%）。在甘肃，年平均气温<8 ℃和年平均降水量200~400 mm的地区，采用硝酸铵分次施肥及灌溉和播种量为26~30 kg·hm^-2时，更有利于添加氮素对苜蓿产量和粗蛋白含量的提高效应及对酸性和中性洗涤纤维含量的降低效应；但适宜的施氮量及生长年限在产量与品质方面存在差异。该研究可为苜蓿生产力提升及氮营养高效利用提供参考。

Effects of nitrogen application on alfalfa yield and quality in China-A Meta-analysis

Nitrogen plays an important role in the yield accumulation and quality improvement of alfalfa. However， supra-optimal nitrogen application to alfalfa crops not only causes a waste of nitrogen resource， but also aggravates environmental pollution. Additionally， the effect of nitrogen application on alfalfa production varies with different regional conditions and management practices. In this study， we searched the peer-reviewed papers reporting the effects of nitrogen application on alfalfa yield and quality， and quantitatively investigated the effect using meta-analysis. It was found that compared with no nitrogen application， nitrogen application significantly improved the yield and quality of alfalfa， and the mean increase in yield and crude protein content was， respectively， 12.6% （with a confidence interval of 9.0% to 16.2%） and 7.3% （with a confidence interval of 4.1% to 10.6%）， and the mean decrease in acid and neutral detergent fiber contents was， respectively， 5.6% （with a confidence interval of 3.5% to 7.8%） and 3.0% （with a confidence interval of 1.0% to 4.9%）. The effect of nitrogen application of increasing alfalfa yield and crude protein content and decreasing acid and neutral detergent fiber content was more pronounced in Gansu， in regions with an annual average temperature of <8 ℃ and an annual average precipitation of 200-400 mm， when using ammonium nitrate in split dressings with part as base fertilizer and part as top dressing， with irrigation， and with sowing rates of 26 to 30 kg·ha^-1. However， there were differences in yield and quality for suitable nitrogen application rates and planting year. This study can provide a reference for the improvement of alfalfa productivity and the efficient utilization of nitrogen nutrition.