氮肥对南洋楹苗木生长及生理特性的影响

Effects of Nitrogen Fertilizer on Growth and Physiological Characteristics of Albizia falcataria Seedlings

南洋楹生长快速,利用价值高,是一种优良的造林树种。良种壮苗是实现人工林高效培育的前提与保障,而氮素是植物生长发育中最重要的营养元素。以南洋楹优树种子培育的实生幼苗为试验材料,采用根施和叶面施肥的方式,探讨了硝态氮肥硝酸钠、铵态氮肥硫酸铵和酰胺态氮肥尿素3种氮素形态氮肥,以0.9 g/(株·月)等纯氮量施用2个月后测定了苗木生长与相关生理指标的变化。结果表明:氮素形态和施氮方式对幼苗生长影响显著,其中在硫酸铵+根施处理下,幼苗高径、生物量增量及根冠比最大,而在硝酸钠+根施处理下,除根冠比外,高径、生物量方面均表现最差。采用根施硫酸铵的方式,叶片中N、P、K含量最高,在根施硝酸钠下,N、P、K含量最低,而Ca含量在根施、叶面施用硫酸铵时均明显偏低。根施硫酸铵显著提升了幼苗叶片光合能力,净光合速率(Pn)、水分利用效率(WUE)较大,蒸腾速率(Tr)、气孔导度(Gs)、胞间二氧化碳浓度(Ci)较小,可溶性糖和可溶性蛋白含量较高。研究结果还表明,采用根外施用铵态氮肥的方式最利于南洋楹幼苗的生长,这为今后开展工厂化南洋楹良种壮苗的培育提供了可靠依据。

Albizia falcataria grows fast with high utilization value. It is an excellent afforestation tree species. Strong seedlings are the premise and guarantee for efficient cultivation of plantations, and nitrogen is the most important nutrient element in plant growth and development. In this experiment, the seedlings cultivated by the seeds of A. falcataria were used as experimental materials, and the three nitrogen forms of nitrate nitrogen fertilizer sodium nitrate, ammonium nitrogen fertilizer ammonium sulfate and amide nitrogen fertilizer urea were discussed by root application and foliar application. The changes of seedling growth and related physiological indexes after 2 months of application of pure nitrogen such as 0.9 g·plant-1month-1 are studied. The results showed that nitrogen forms and nitrogen application methods had significant effects on seedling growth. Under the treatment of ammonium sulfate + root application, the seedling height, biomass increment and root-shoot ratio were the largest, while under the treatment of sodium nitrate + root application, except for root-shoot ratio, the height and biomass were the worst. The content of N, P and K in leaves was the highest by root application of ammonium sulfate, while the content of N, P and K was the lowest by root application of sodium nitrate, while the content of Ca was significantly lower by root application and foliar application of ammonium sulfate. Root application of ammonium sulfate significantly increased the photosynthetic capacity of seedling leaves. Net photosynthetic rate(Pn) and water use efficiency(WUE) were higher. Transpiration rate(Tr), stomatal conductance(Gs) and intercellular carbon dioxide concentration(Ci) were lower, and soluble sugar and soluble protein content were higher. The results showed that the application of ammonium nitrogen fertilizer outside the root was the most conducive to the growth of A. falcataria seedlings, which provided a reliable basis for the cultivation of A. falcataria seedlings in the future.