Stefan Laura, Hartmann Martin, Engbersen Nadine, Six Johan, Schöb Christian
Institute of Agricultural Sciences, Department of Environmental Systems Science, ETH Zürich, Zurich, Switzerland.
Front Microbiol. 2021 Apr 15;12:660749. doi: 10.3389/fmicb.2021.660749. eCollection 2021.
Intensive agriculture has major negative impacts on ecosystem diversity and functioning, including that of soils. The associated reduction of soil biodiversity and essential soil functions, such as nutrient cycling, can restrict plant growth and crop yield. By increasing plant diversity in agricultural systems, intercropping could be a promising way to foster soil microbial diversity and functioning. However, plant-microbe interactions and the extent to which they influence crop yield under field conditions are still poorly understood. In this study, we performed an extensive intercropping experiment using eight crop species and 40 different crop mixtures to investigate how crop diversity affects soil microbial diversity and activity, and whether these changes subsequently affect crop yield. Experiments were carried out in mesocosms under natural conditions in Switzerland and in Spain, two countries with drastically different soils and climate, and our crop communities included either one, two or four species. We sampled and sequenced soil microbial DNA to assess soil microbial diversity, and measured soil basal respiration as a proxy for soil activity. Results indicate that in Switzerland, increasing crop diversity led to shifts in soil microbial community composition, and in particular to an increase of several plant-growth promoting microbes, such as members of the bacterial phylum . These shifts in community composition subsequently led to a 15 and 35% increase in crop yield in 2 and 4-species mixtures, respectively. This suggests that the positive effects of crop diversity on crop productivity can partially be explained by changes in soil microbial composition. However, the effects of crop diversity on soil microbes were relatively small compared to the effects of abiotic factors such as fertilization (three times larger) or soil moisture (three times larger). Furthermore, these processes were context-dependent: in Spain, where resources were limited, soil microbial communities did not respond to crop diversity, and their effect on crop yield was less strong. This research highlights the potential beneficial role of soil microbial communities in intercropping systems, while also reflecting on the relative importance of crop diversity compared to abiotic drivers of microbiomes and emphasizing the context-dependence of crop-microbe relationships.
集约农业对生态系统多样性及功能，包括土壤的生态系统多样性及功能具有重大负面影响。土壤生物多样性及诸如养分循环等基本土壤功能的相关减少，会限制植物生长和作物产量。通过增加农业系统中的植物多样性，间作可能是促进土壤微生物多样性及功能的一种有前景的方式。然而，在田间条件下植物与微生物的相互作用以及它们对作物产量的影响程度仍知之甚少。在本研究中，我们使用八个作物品种和40种不同的作物混合物进行了一项广泛的间作实验，以研究作物多样性如何影响土壤微生物多样性和活性，以及这些变化随后是否会影响作物产量。实验在瑞士和西班牙的自然条件下的中型生态系统中进行，这两个国家的土壤和气候差异极大，我们的作物群落包括一、二或四个品种。我们对土壤微生物DNA进行采样和测序以评估土壤微生物多样性，并测量土壤基础呼吸作为土壤活性的指标。结果表明，在瑞士，增加作物多样性导致土壤微生物群落组成发生变化，特别是几种促进植物生长的微生物增加，例如细菌门的成员。群落组成的这些变化随后分别导致两品种和四品种混合物的作物产量提高了15%和35%。这表明作物多样性对作物生产力的积极影响部分可由土壤微生物组成的变化来解释。然而，与施肥（大三倍）或土壤湿度（大三倍）等非生物因素的影响相比，作物多样性对土壤微生物的影响相对较小。此外，这些过程取决于具体情况：在资源有限的西班牙，土壤微生物群落对作物多样性没有反应，它们对作物产量的影响也较弱。这项研究突出了土壤微生物群落在间作系统中的潜在有益作用，同时也思考了作物多样性相对于微生物群落非生物驱动因素的相对重要性，并强调了作物与微生物关系的情境依赖性。
