苹果园种植牧草对幼树生长及^(15)N–尿素吸收、利用的影响

Effect of Planting Herbage on the Growth and Absorption,Utilization of ^(15)N-urea of Apple Saplings

以两年生红富士/平邑甜茶为试材,采用田间小区试验及15N同位素标记示踪法,研究了低氮(50 kg·hm-2)和中氮(100 kg·hm-2)条件下分别种植3种牧草(白三叶、黑麦草和鼠茅草)对苹果幼树生长及15N–尿素吸收、利用的影响。结果表明,春梢停长期,与单作苹果相比,种植牧草后苹果植株生物量、吸氮量及15N肥料利用率显著降低,这在低氮处理下尤为明显;而到秋梢停长期,与单作苹果相比,种植牧草后苹果植株生物量、吸氮量、15N肥料利用率及根系活力显著提高。至秋梢停长期,0~20cm土层15N丰度及总氮含量为种植白三叶>种植鼠茅草>种植黑麦草>单作苹果,而在20~40 cm及40~60 cm土层15N丰度及总氮含量为单作苹果>种植黑麦草>种植鼠茅草>种植白三叶,表明种植白三叶、黑麦草和鼠茅草降低了氮素的淋溶损失,有利于氮肥的保持,从而提高氮肥利用率,促进苹果幼树的生长。

The effect of planting three kinds of herbage(Trifolium repens Linn.,Lolium perenne L. and Vulpia myuros C.)on the growth and absorption of 15 N were studied in field plot using the 15N-labeled tracer method on low nitrogen level(50 kg · hm-2)and mid nitrogen level(100 kg · hm-2)in 2-year-old‘Red Fuji'/Malus hupenensis apple saplings. The results showed that,compared with apple monocrops,the biomass,nitrogen acquisition and 15 N utilization rate of apple saplings were significantly reduced by planting herbage which was especially true under low nitrogen treatment in spring shoots growth arrest stage;While in autumn shoots growth arrest stage,compared with apple monocrops,the biomass,nitrogen acquisition,15 N utilization rate and root activity of apple saplings were significantly increased by planting herbage. In autumn shoots growth arrest stage,the 15 N abundance and total N content in 0–20 cm layer were Trifolium repens Linn. planting > Vulpia myuros C. planting > Lolium perenne L. planting > apple monocrops,but in 20–40 cm and 40–60 cm layer the 15 N abundance and total N content were apple monocrops > Lolium perenne L. planting > Vulpia myuros C. planting > Trifolium repens Linn. planting. It indicated that leaching loss of nitrogen fertilizer was reduced by planting Trifolium repens Linn.,Lolium perenne L. and Vulpia myuros C. Gmelin,which benefiting soil fertility remaining but also increasing the nitrogen efficiency,promoting the growth of apple saplings.