A research team led by Prof. ZENG Fanjiang from the Xinjiang Institute of Ecology and Geography of the Chinese Academy of Sciences has figured out why cotton yields go up with short-term fertilization but drop with long-term fertilization. The findings were recently published in the journal Agriculture, Ecosystems & Environment.

In desert farmlands that have been turned into cropland, fertilization can boost crop yields. But over time, adding chemical and organic nutrients can also cause soil to become too acidic or too alkaline, and throw off its nutrient balance. So, finding a balance between short-term gains and long-term soil health is key to keeping desert farming sustainable.

The team focused on cotton and soil in reclaimed desert farmland along the southern edge of the Taklimakan Desert from 2010 to 2020. They set up three fertilization treatments: high manure fertilizer, normal manure fertilizer, and a non-fertilized control.

They looked closely at the physical and chemical properties, nutrient stocks, micronutrient availability, and cotton growth in both the topsoil (0–10 cm) and subsoil (10–20 cm).

The results showed that long-term fertilization significantly raised soil organic carbon and available nutrient levels in the topsoil, but it drained organic carbon from the subsoil.

This "topsoil enrichment and subsoil depletion" of carbon weakened the deeper soil's ability to buffer nutrients and supply water. As a result, cotton yields first increased with short-term fertilization, but then started to drop with long-term fertilization.

These findings offer a scientific guide for managing nutrients more wisely in desert oasis farmlands.