Sustainability Evaluation of the Maize–Soybean Intercropping System and Maize Monocropping System in the North China Plain Based on Field Experiments

Xiaolei Yang,Xiaolong Wang,Yuanquan Chen,James Gerber,Dong Wang,Yawen Shen,Peng Sui,Hongcui Dai

doi:10.3390/agronomy8110268

Abstract

Monocropping systems, which currently dominate China’s major grain production regions, contribute to resource scarcity and environmental pollution. Intercropping has the potential to improve resource use efficiency. However, prior studies of intercropping systems have generally focused on ecological, economic, and social consequences. Here, we make a comparative ecological sustainability analysis on energy capture and efficiency of maize monocropping and maize–soybean intercropping systems through emergy evaluation based on field experiments performed from 2012 to 2014. We find that maize monocropping shows higher sustainability than maize–soybean intercropping in the North China Plain at present. Quantitative results indicate that for maize monocropping, the emergy yield ratio (EYR) and emergy sustainability index (ESI) are 13.7% and 21.1% higher than that of intercropping systems, and the environmental loading ratio (ELR) is 7.3% lower than that of intercropping systems. To further test, we applied three levels of nitrogen fertilizer in intercropping systems (120 kg ha−1, 180 kg ha−1, 240 kg ha−1), and find that a reduced rate of N fertilizer for intercropped system leads to higher sustainability (ESI 5.3% higher) but still lower sustainability than maize monocropping. Key drivers of the different sustainability outcomes are decreased energy output and a larger proportion of labor input associated with intercropping systems.

Highlights

Increased crop demand by a growing population and changing diets poses a variety of sustainability challenges to the global agricultural system [1,2], including food insecurity [3], accompanied by scarcity of natural resources [4,5], pollution of ground water [6], excessive application of chemical fertilizer [7], substantial losses of biodiversity [8] and climate change [9], which are ongoing issues
We find the emergy sustainability index (ESI) of maize monocropping in this experiment is 0.23, while the ESI of maize–soybean intercropping is 0.19 (Table 5), indicating that maize monocropping has greater sustainability than maize–soybean intercropping
Because of the strengths researchers found in cereal–legume intercropping, on the premise of ensuring the maize production, it has been proposed that developing maize–soybean intercropping will improve the ecological function of the maize production area, which would be beneficial in the North China Plain [13]

Summary

Introduction

Increased crop demand by a growing population and changing diets poses a variety of sustainability challenges to the global agricultural system [1,2], including food insecurity [3], accompanied by scarcity of natural resources [4,5], pollution of ground water [6], excessive application of chemical fertilizer [7], substantial losses of biodiversity [8] and climate change [9], which are ongoing issues. Agricultural practices determine the level of food production, even the state of the global environment [2]. These global scale issues play out within China as well. In response to domestic demand and government policies, China’s agricultural sector has nearly doubled grain production from 1980 to Agronomy 2018, 8, 268; doi:10.3390/agronomy8110268 www.mdpi.com/journal/agronomy. The North China Plain (NCP) is one of the major grain production areas in China, with 35 million ha of croplands, and the wheat–maize double cropping rotation dominant over 14 million ha [11,12]

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Conclusion