Qiao Hang, Cheng Hui, Li Tiantian, Fan Wenxia, Zhao Yaru, Cui Zhengjun, Wang Jinbin, Yang Qingqing, Jia Chengze, Zhang Wei, Chen Guodong, Wan Sumei
College of Agriculture, Tarim University, Alar 843300, China.
Key Laboratory of Genetic Improvement and Efficient Production for Specialty Crops in Arid Southern Xinjiang of Xinjiang Corps, Tarim University, Alar 843300, China.
Plants (Basel). 2025 Jul 3;14(13):2048. doi: 10.3390/plants14132048.
Intercropping legumes offers a sustainable approach to enhance resource efficiency and yields, yet the effects of different legume densities and nitrogen addition levels on soil quality within such systems remain unclear. We conducted a comparative analysis of crop yield, nitrogen use efficiency, and soil quality between intercropping and monoculture systems, and further examined the effects of four planting densities (D1: 210 kg ha, six rows; D2: 280 kg ha, eight rows; D3: 350 kg ha, ten rows) and four nitrogen application levels (N0: 0 kg ha; N1: 80 kg ha; N2: 160 kg ha; N3: 240 kg ha) within a jujube-alfalfa ( Mill. and L. respectively) intercropping system. The results showed that intercropping significantly enhanced land productivity within the agricultural system, with the highest yields (alfalfa: 13790 kg ha; jujube: 3825 kg ha) achieved at an alfalfa planting density of 280 kg ha. While the intercropping systems generally improved productivity, an alfalfa planting density of 350 kg ha resulted in an actual yield loss due to excessive nutrient competition at higher densities. As the planting density of alfalfa increased, its competitive ratio declined, whereas the competitive ratio of jujube trees increased. Compared to monocropping systems, intercropping systems demonstrated a clear trend of enhanced nitrogen utilization efficiency and improved soil quality, particularly at an alfalfa planting density of 280 kg ha. At an alfalfa density of 280 kg ha, the intercropping system exhibited increases of 15.13% in nitrogen use efficiency (NUE), 46.60% in nitrogen partial factor productivity (NPFP), and 32.74% in nitrogen nutrition index (NNI), as well as improvements in soil quality of 19.53% at a depth of 0-20 cm and 15.59% at a depth of 20-40 cm, compared to the monoculture system. Further analysis revealed that nitrogen utilization efficiency initially increased and then decreased with a rising competitive ratio of alfalfa. Accordingly, soil quality was improved along with the enhanced nitrogen utilization efficiency. Thus, at an alfalfa planting density of 280 kg ha, resource use efficiency and soil quality were maximized as a result of optimal interspecific competitiveness and the highest nitrogen use efficiency, with minimal influence from the application of nitrogen fertilizer.
间作豆科植物为提高资源利用效率和产量提供了一种可持续的方法，然而不同豆科植物密度和施氮水平对这类系统中土壤质量的影响仍不清楚。我们对间作和单作系统之间的作物产量、氮素利用效率和土壤质量进行了比较分析，并进一步研究了枣 - 苜蓿（分别为 枣和 苜蓿）间作系统中四种种植密度（D1：210 千克/公顷，6 行；D2：280 千克/公顷，8 行；D3：350 千克/公顷，10 行）和四种施氮水平（N0：0 千克/公顷；N1：80 千克/公顷；N2：160 千克/公顷；N3：240 千克/公顷）的影响。结果表明，间作显著提高了农业系统中的土地生产力，苜蓿种植密度为 280 千克/公顷时产量最高（苜蓿：13790 千克/公顷；枣：3825 千克/公顷）。虽然间作系统总体上提高了生产力，但苜蓿种植密度为 350 千克/公顷时，由于较高密度下养分竞争过度，实际产量下降。随着苜蓿种植密度的增加，其竞争比下降，而枣树的竞争比增加。与单作系统相比，间作系统呈现出氮素利用效率提高和土壤质量改善的明显趋势，特别是在苜蓿种植密度为 280 千克/公顷时。在苜蓿密度为 280 千克/公顷时，与单作系统相比，间作系统的氮素利用效率（NUE）提高了 15.13%，氮素偏生产力（NPFP）提高了 46.60%，氮素营养指数（NNI）提高了 32.74%，0 - 20 厘米深度的土壤质量提高了 19.53%，20 - 40 厘米深度的土壤质量提高了 15.59%。进一步分析表明，氮素利用效率随着苜蓿竞争比的增加先升高后降低。相应地，土壤质量随着氮素利用效率的提高而改善。因此，在苜蓿种植密度为 280 千克/公顷时，由于种间竞争力最佳和氮素利用效率最高，资源利用效率和土壤质量达到最大化，氮肥施用的影响最小。
