A researcher team led by Prof. WANG Kelin from the Institute of Subtropical Agriculture of the Chinese Academy of Sciences conducted a regional-scale sampling in a karst region in southern China,,and revealed the microbial mechanisms that limit the phosphorus (P) cycle in farmland soils.

Their study was published in Agriculture, Ecosystems and Environment on January13.

Phosphorus shortage in soil is a worldwide challenge for agriculture. Soil microbes play key roles in mobilizing this vital nutrient, making it available to crops. However, common farming activities might disrupt this delicate system. We still don't fully understand how agricultural activities affect these microbial communities and their ability to solve phosphorus shortages.

Along a gradient of low to high agricultural disturbance, the team studied four typical farmland types in the region's two main soils (calcareous and red soil): pasture, sugarcane farmland, rice paddy fields, and maize croplands.

They found that high-intensity farming (more tillage, fertilizer, and pesticides) increases genes related to microbial phosphorus starvation while reducing the abundance of key genes that help solubilize and transport phosphorus for crops. Alkaline calcareous soil naturally hosts a higher abundance and diversity of phosphorus-cycling microbes and their functional genes compared to acidic red soil. This is largely because its near-neutral pH is more favorable for microbial activity. Interestingly, in stressful acidic red soil, there is a strong link between the diversity of microbial species and the diversity of their phosphorus-cycling functions. However, in the more favorable calcareous soil, this link breaks down ("decouples"). Here, higher species diversity does not automatically mean greater functional diversity, showing that simply having more microbial species doesn't guarantee better phosphorus cycling.

"We found that high-intensity farming weakens the functional capacity of soil microbes that cycle phosphorus. This appears to be a core reason behind phosphorus limitation in agricultural soils.” said Prof. ZHAO Jie, the corresponding author of the study. “This insight helps us design better strategies for sustainably managing this essential nutrient."

Contact: Jie Zhao

E-mail:jzhao@isa.ac.cn

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