根系互作对苹果生长及15N-尿素吸收、利用和土壤残留的影响

在苹果/白三叶(M1)和苹果/黑麦草(M2)复合系统中,设置根系分隔(完全分隔N1、尼龙网分隔N2、不分隔N3),采用~(15) N同位素示踪技术,研究了根系互作对苹果生长及~(15) N吸收、利用,损失和土壤残留的影响。结果表明:苹果新梢旺长期,在M1中苹果各生长指标均为N3N2N1,在M2中趋势相反。与N1处理相比,M1中N2和N3处理苹果~(15) N利用率分别增加了11.91%和18.96%,M2中分别降低了5.76%和8.99%,苹果全氮量和~(15) N吸收量趋势相同。苹果根区土壤~(15) N丰度、总氮含量和~(15) N残留率均以N1处理最高,N3处理最低;苹果落叶期,两种复合体系中均以N3处理的苹果各生长指标最大,N1处理最低。在M1中N2和N3处理苹果根区土壤~(15) N丰度分别比N1处理增加了22.33%和34.15%,在M2中增幅分别为13.73%和21.44%,土壤总氮含量呈相同趋势。M1和M2中苹果全氮量、~(15) N吸收量和各器官Ndff值差异显著,均为N3N2N1。与N1处理相比,M1中N2和N3处理下苹果~(15) N利用率分别增加了19.11%和42.66%,而~(15) N损失率分别降低了13.55%和27.12%,在M2中趋势相同。苹果生长前期,黑麦草和苹果以负相竞争为主,白三叶对其促进效果亦不显著。而至苹果生长后期,两种牧草和苹果根系互作降低了苹果根区氮素损失,促进了苹果的氮素吸收利用和营养生长,且以间作白三叶效果最好。

Effects of Root Interaction on the Apple Tree Growth, and Absorption, Utilization and Soil Residue of 15N-urea

A pot experiment was carried out in apple-Trifolium repens Linn. (M1) and apple-Lolium perenne L. (M2) intercropping system to investigate the effects of root interaction on the growth and ¹⁵N-urea absorption, utilization, loss and residue of apple trees under different root barrier method (N1, N2 and N3 were equivalent to solid barrier, mesh barrier and no barrier, respectively), using the ¹⁵N-labeled tracer technique. Results showed that, at new shoot growing stage, the growth index of apple trees displayed an order of N3 > N2 > N1 in M1 intercropping system, while the opposite tendency was observed in M2 intercropping system. Compared with N1 treatment, the ¹⁵N utilization rate of apple trees increased by 11.91% and 18.96% in M1 intercropping system under N2 and N3 treatment, but decreased by 5.76% and 8.99% in M2 intercropping system. The plant total N content and ¹⁵N absorption amount showed the same tendency. The effect on ¹⁵N abundance and total N content in the soil of apple trees were the most significant in N1 treatment, and the least in N3 treatment. At leaf fall period, the growth index of apple trees was obviously the highest in N3 treatment, and the lowest was found in N1 treatment. In comparison with N1 treatment, the soil ¹⁵N abundance of apple trees under N2 and N3 treatment increased by 22.33% and 34.15% in M1 intercropping system, and the rate of increase in M2 intercropping system were 13.73% and 21.44%, the total N content in the soil of apple trees showed the same tendency. There were significant differences in plant total N content,¹⁵N absorption amount and Ndff value among the treatments, which was in a trend of N3 > N2 > N1 in M1 and M2 intercropping system. The ¹⁵N utilization rate of apple trees under N2 and N3 treatment were 19.11% and 42.66% higher than that of N1 treatment, with the ¹⁵N loss rate were 13.55% and 27.12% lower than that of N1 treatment in M1 intercropping system, the same trend was showed in M2 intercropping system. Overall findings showed that it mainly showed a competitive effect in apple-Lolium perenne L. intercropping system and a relatively minor positive effect in apple-Trifolium repens Linn. intercropping system during early stages of apple growth. While in the later period of apple growth, the root interaction in forage grasses and apple trees reduced nitrogen loss and consequently improved the absorption, utilization of nitrogen nutrition and the growth of apple trees by a certain degree, and Trifolium repens Linn. played a better effect than Lolium perenne L.