How climate change influences paddy soil nitrogen pool in northeastern China

Plant nitrogen (N) acquisition is essential to crop growth and yield. However, how plant N uptake and N origin (soil-derived N or fertilizer-derived N) respond to elevated atmospheric CO₂ and warming remains largely unknown.

Recently, researchers from the Northeast Institute of Geography and Agroecology (IGA) of the Chinese Academy of Sciences investigated the soil- or fertilizer-derived N uptake and yield of different cultivars of rice in response to climate change in northeast China.

Related findings were published in Agricultural and Forest Meteorology.

The researchers found that elevated CO₂ and warming significantly increased plant N uptake, and soil-N rather than fertilizer-N was the source of the increased N uptake.

The increased soil-N uptake resulted in the enhancement of rice yield under climate change. Urea application did not alter the yield response to elevated CO₂ and warming compared to the non-N supply, but did stimulate plant uptake of the soil-derived N.

The researchers also examined the impacts of climate change on N mineralization and relevant microbial mechanisms in the rhizosphere of rice plants. The study was published in Biology and Fertility of Soils.

They found that co-elevation of CO₂ and temperature increased microbial biomass C and N, as well as N mineralization. The absolute abundances of the N-mineralization genes chi, pea, pan, and urea hydrolysis gene ureC in the rhizosphere also increased under elevated CO₂ and warming, corresponding to the additional N mineralization and photosynthetic C allocation into the soil.

These studies suggested that climate change may lead to the depletion of the recalcitrant soil N pool in paddy soils, and that fertilizer-N-use efficiency may need to be factored into future breeding for rice genotypes adapting well to climate change. Co-elevation of CO₂ and temperature stimulated microbially mediated soil N mineralization in the rhizosphere of rice, posing a risk on the acceleration of soil organic matter decomposition.