Nitrogen (N) application is the major agronomic measures to increase and maintain crop yields. 

However, excessive artificial N application not only wastes resources, causes soil degradation, but also pollutes water bodies and the atmosphere. Quantifying the fates and utilization efficiency of fertilizer N in different crop production regions and between different crop-types is thus highly important to N fertilizer management on cropland. Maize is one of the most important crops and its cropping area and yield have exceeded wheat and rice in China.

However, studies on Nitrogen Use Efficiency (NUE) and fates of fertilizer N in maize cropping systems were mainly performed in North China, but inadequately in Northeast China where maize cropping was rapidly increasing.

QU Zhi, LI Shanlong, FANG Yunting of the Stable Isotope Ecology Group at the Institute of Applied Ecology (IAE), Chinese Academy of Sciences, together with their colleagues, conducted six in-situ 15N tracing experiments and compared fates and use efficiency of fertilizer N in maize cropping systems in North and Northeast China.

The researchers found that an average of 34% of the fertilizer N was taken up by standing crops within a single growing-season, with a residue of 35% in the soil and a loss of 31% to water bodies and the atmosphere. NUE was higher (47%) but N loss (21%) was lower in Northeast compared to that (28% and 34%, respectively) in North China.

The higher NUE was probably associated to higher maize production and thus higher N uptake.

Compared to climatic factors, soil properties were of even more importance to the regional differences in N use and loss.

In addition, the researcher found that 64% of maize N was from soil mineralization and nitrification (i.e. soil N) rather than from fertilizers.

This work entitled “Fertilizer nitrogen use efficiency and fates in maize cropping systems across China: Field ¹⁵N tracer studies“ has been recently published in the journal Soil and Tillage.

The study was funded by the Priority Science & Technology Programme of the Chinese Academy of Sciences, the National Key Research and Development Program and the National Natural Science Foundation of China.