The sustainability of agricultural ecosystems relies on the soil micro-food webs, the "hidden underground engine." Revealing the properties, functions, and interaction patterns of the internal members of the micro-food soil web will provide important insights for the sustainable management of agriculture.

To address this challenge, researchers led by Prof. Kelin Wang from the Institute of Subtropical Agriculture, Chinese Academy of Sciences, conducted a serial investigation to assess soil carbon, nitrogen, and phosphorus cycling processes and belowground biota community properties, function, and their interaction pattern in karst farmland regions of Southwest China and explored the relationship among these factors along a gradient of low to high agricultural management (Fig. 1).

The study found that, as agricultural intensification increases, the abundance of functional genes associated with soil phosphorus starvation rises, while genes involved in phosphorus solubilization, mineralization, and transport gradually decline (Fig. 2). Correspondingly, the soil available phosphorus content decreases with greater agricultural disturbance. This suggests that adopting conservation farming practices, such as planting pasture, can enhance soil phosphorus cycling and alleviate phosphorus limitation. However, microbial involvement in phosphorus cycling is closely linked to carbon and nitrogen cycling processes. In relatively mild, mid-alkaline calcareous soils, bacterial species are highly abundant, and carbon and nitrogen cycles proceed more rapidly (Fig. 3). This provides ample resources for microbial growth and reproduction, contributing to greater soil organic carbon accumulation. In contrast, in nutrient-poor acidic red soils, fungal species dominate. Here, microbes allocate more energy to survival rather than growth, slowing down carbon and nitrogen cycling (Fig. 3). Notably, intensive agricultural management may weaken the carbon sequestration capacity of bacteria and slow soil carbon and nitrogen cycling, potentially triggering positive carbon-climate feedback (Fig. 4). Beyond microbes, soil also hosts other organisms such as viruses and soil fauna. Their interactions form a complex soil micro-food web, which is expected to significantly influence broader soil functions, including nutrient cycling, water retention, soil structure improvement, and plant disease suppression. By integrating molecular sequencing with field measurements, the researchers observed that conservation agriculture enhances the stability of belowground communities (Fig. 5). This stability helps maintain high soil functionality even under environmental stress, supporting sustainable crop yields (Fig. 6). Particularly, soil fauna can stabilize the entire soil biota community through top-down regulation. This highlights the need for agricultural practices to focus not only on soil microbes but also on protecting the soil fauna abundance and diversity.

“Our research on the soil micro-food web properties and function under varying soil conditions and agricultural disturbances in karst agroecosystems helps clarify the underground biological mechanisms driving soil functions, especially in the context of global agricultural intensification.” said Prof. Jie Zhao , the corresponding author of the study. “This will provide a scientific basis for formulating more sustainable agricultural policies.”

Contact: Jie Zhao

E-mail:jzhao@isa.ac.cn

Fig.1 Selected 4 agricultural land use types in this study (Image by Xianwen Long).

Fig.2 Abundance of P-cycling functional genes as affected by different land use types and soil types (Image by Xianwen Long)

Fig.3 Functional potentials of microbiomes in calcareous soil and red soil (Image by Xianwen Long)

Fig.4 Microbial driving mechanisms of soil carbon sequestration and decomposition potential (Image by Xianwen Long)

Fig.5 Drivers of soil biota network complexity and stability (Image by Xianwen Long)

Fig.6 The relationship between soil multifunctionality and community stability of organisms (Image by Xianwen Long)