Region-specific nitrogen management indexes for sustainable cereal production in China

Liu Xuejun,Liu Zitong,Li Tingyu,Cao Hanbing,Yin Yulong,Zhang Qingsong,Oene Oenema,Ying Hao,Cui Zhenling,Zhang Fusuo,Qin Wei,Wim de Vries,Ren Siyang,Zhang Weifeng,Ju Xiaotang

doi:10.1088/2515-7620/aba12d

Abstract

Effective policy measures are required to control environmental problems caused by nitrogen (N) fertilizer use in intensive crop production systems in China. However, simply reducing the use of N fertilizer in all regions may be detrimental to food security. Here we reviewed N management policies and indicators, with a particular focus on European Union (EU), and designed an N index system for cereal crops in China. We suggest to use N surplus as an (environmental) evaluation index and N input as a guide to meet the dual challenge of food security and environmental sustainability, and propose crop and region-specific standards for these indexes. We inferred a mean critical N surplus of 75 kg N ha−1 for maize, 40 kg N ha−1 for wheat and 70 kg N ha−1 for rice. For N input, Maximum N (Max. N) and Minimum N (Min. N) input indices are proposed, to guide farming practices effectively. Max. N was based on the N demand of crops achieving their potential yield, in different regions, Min. N was based on the N demand of crops at their target yield, while associated N surpluses do not exceed the set critical values. To meet the dual challenge of food security and environmental sustainability, China needs to increase maize and wheat yields by 20%–40% (rice has achieved target yield) while reducing N input by 10%–20%. This requires an enormous increase in N use efficiency. The N management indexes proposed here can be used as benchmarks to monitor the progress at regional level. Max. N and Min. N may have to be updated regularly when potential and target yields, and thereby crop N demand, change. Also, critical N surpluses may have to change when insights in the impacts of these N surpluses change.

Highlights

Environmental pollution and soil acidification caused by nitrogen (N) fertilizer use in China have received significant attention during the last decade (Ju et al 2009, Guo et al 2010, Liu et al 2010, Zhang et al 2015, Yu et al 2019)
Developing N management indexes in China There are a number of elements that need to be addressed for a sound agri-environmental management policy: (1) the objectives, (2) the policy instruments, (3) the target areas and scale, (4) the addressees (Oenema 2004)
At the critical N surplus, the corresponding seasonal reactive N emissions in maize, wheat and rice cropping systems were 6–25 kg N ha−1 for NO3− leaching, 0.54–1.13 kg N ha−1 for N2O emissions, and 28–36 kg N ha−1 for NH3 emissions. Most of these N losses are within the safe range regarding environmental impact on water and air quality, with the exception of NO3− leaching from maize (25 kg ha−1), which slightly exceeded the critical level of 18 kg ha−1

Summary

Introduction

Environmental pollution and soil acidification caused by nitrogen (N) fertilizer use in China have received significant attention during the last decade (Ju et al 2009, Guo et al 2010, Liu et al 2010, Zhang et al 2015, Yu et al 2019). Series of governmental policies have been released to improve N fertilizer management in intensive cropping systems. The governmental policy related to ‘replacing inorganic fertilizer by organic fertilizer’ in fruit, vegetable and tea cropping systems has led to incidental misuse and overuse of animal manure, due to a lack of guidance and knowledge (Farmer survey 2019). There is an urgent need for guidance in nutrient management, including benchmark indexes, to be able to improve the use of both synthetic and organic fertilizers and to meet the dual challenges of food security and environmental sustainability in China

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