土壤水分和施氮水平对紫花苜蓿苗期生长的互作效应分析

土壤水分含量对作物施肥效应有重要影响。为了研究长江中下游农区土壤条件下施氮对紫花苜蓿生长的影响,探究土壤水分和施氮水平的互作效应,进行了盆栽半控制试验。试验采用两因素随机区组设计,设置了3个土壤水分水平(分别为50%、70%、90%的最大持水量)和4个施氮水平(0、90、180和270 kg/hm²)。结果表明,在施氮量一定的条件下,适当提高土壤水分含量,紫花苜蓿苗期生长、地上部干物质积累及氮素利用率均呈现增加的趋势。在相同土壤水分水平下,适量施氮可以促进紫花苜蓿生长、地上部干物质积累及氮素的利用,但是过多施氮不利于地上部干物质积累及氮素利用率的提高。土壤水分和施氮水平具有显著的互作效应。回归分析结果表明,施氮效应因土壤水分含量升高而显著增大;适宜的施氮量也因土壤水分含量升高而增大。因此,土壤缺水的地区或季节,施肥与灌溉应同步进行;土壤水分含量较高的长江中下游农区,适当增施氮肥有利于紫花苜蓿高产,并提高氮素利用率。

Interactive effects of soil moisture and nitrogen application rate on seedling growth of alfalfa

Soil moisture significantly affects crop response to fertilizer application.This study investigated the effect of nitrogen application on the growth of alfalfa (Medicago sativa) in the middle and lower reaches of the Yangtze River and evaluated the interaction between soil moisture and nitrogen application rate effects with a semi-controlled pot experiment conducted in Nanjing.The experiment included three soil moisture levels (50％,70％ and 90％ of maximum water holding capacity) and four nitrogen application rates (0,90,180,270 kg/ha).Dry matter accumulation and nitrogen use efficiency increased with increasing soil moisture level.Under the same soil moisture level,dry matter accumulation and nitrogen use efficiency increased with appropriate N application rates,but decreased with excess nitrogen application.The interaction effect between soil moisture and nitrogen application rate was statistically significant.The effect of fertilizer nitrogen was significantly enhanced at higher soil moisture levels.With increased soil moisture,the effect of nitrogen application at moderate rates was also enhanced.Therefore,when soil moisture level is lower,nitrogen application should be carried out with irrigation.In the middle and lower reaches of the Yangtze River where there is high soil moisture,more nitrogen application could increase forage yield and nitrogen use efficiency of alfalfa.