Researchers from the Institute of Applied Ecology of the Chinese Academy of Sciences have found a promising approach to reducing fertilizer nitrogen loss in China's black soil region. The study, published in the journal Agriculture, Ecosystems & Environment, examines the effects of no-tillage farming combined with straw mulching. 

Chemical fertilizers are critical to increasing crop yields, but their overuse can lead to environmental problems. Nitrogen, a key component of these fertilizers, can leach into groundwater and cause pollution. 

In this study, the researchers used a technique called nitrogen (¹⁵N) isotope tracing to track nitrogen movement in a three-year field experiment. Their findings revealed a critical depth for nitrate leaching loss in the black soil. While 99% of crop roots remain within the top 120 cm of soil layer, a significant portion (up to 7%) of fertilizer nitrogen leaches deeper as nitrate, becoming unavailable to plants and contributing to losses. 

They showed that no-tillage with straw mulch is a potential solution. This technique significantly improves nitrogen use efficiency and crop yields. It reduces the conversion of fertilizer nitrogen to mineral nitrogen, an easily leachable form of nitrogen, by an average of 36% compared to traditional ridge tillage. It also slows down the downward movement of fertilizer nitrogen, resulting in up to 43% less leaching loss. 

The researchers suggest that no-tillage with 33% or 100% straw mulch is most effective in the black soil region of northeast China. This approach not only maximizes fertilizer nitrogen use, but also increases crop yields and minimizes nitrate leaching losses compared to both 67% mulch and no-tillage without straw mulch. 

These results provide valuable insights for promoting sustainable agricultural practices in China's black soil region.