Developing sustainable summer maize production for smallholder farmers in the North China

Developing sustainable summer maize production for smallholder farmers in the North China Plain:

An agronomic diagnosis method

CHEN Guang-feng1, 3, 4, CAO Hong-zhu2, CHEN Dong-dong2, ZHANG Ling-bo1, ZHAO Wei-li1,ZHANG Yu1, MA Wen-qi2, JIANG Rong-feng1, 3, ZHANG Hong-yan1, 3, ZHANG Fu-suo1, 3

【摘 要】Abstract With an increasing population and changing diet structure, summer maize is increasingly becoming an important energy crop in China. However, traditional farmer practices for maize production are inefficient and unsustainable. To ensure food security and sustainable development of summer maize production in China, an improved, more sustainable farmer management system is needed. Establishing this system requires a comprehensive understanding of the limitations of current farming practice and the ways it could be improved. In our study, 235 plots from three villages in the North China Plain (NCP) were monitored. Maize production on farms was evaluated； our results showed that the maize yield and nitrogen partial factor productivity (PFPN) were variable on smallholder farms at 6.6-13.7 t ha-1 and 15.4-88.7 kg kg-1, respectively.Traditional farming practices also have a large environmental impact (nitrogen surplus: -64.2-323.78 kg ha-1). Key yield components were identified by agronomic diagnosis. Grain yield depend heavily on grain numbers per hectare rather than on

the 1 000-grain weight. A set of improved management practices (IP) for maize production was designed by employing a boundary line (BL) approach and tested on farms. Results showed that the IP could increase yield by 18.4% and PFPN by 31.1%, compared with traditional farmer practices (FP), and reduce the nitrogen (N) surplus by 57.9 kg ha-1. However,in terms of IP effect, there was a large heterogeneity among different smallholder farmers' fields, meaning that, precise technologies were needed in different sites especially for N fertilizer management. Our results are valuable for policymakers and smallholder farmers for meeting the objectives of green development in agricultural production. 【期刊名称】《农业科学学报（英文版）》 【年(卷),期】2024(018)008 【总页数】13

【关键词】Keywords: smallholder farmers, sustainable production, yield gap, agronomic diagnosis, North China Plain

Received 22 June, 2024 Accepted 5 November, 2024 CHEN

Guang-feng,

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mail:xiaofengsdau@126.com； Correspondence ZHANG Hong-yan,Mobile: +86-13718372760, E-mail: zhanghy@cau.edu.cn

? 2024 CAAS. Published by Elsevier Ltd. This is an open access article under

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1. Introduction

Increasing population and environmental degradation have placed unprecedented pressures on agricultural and natural resources, due to dietary changes and bioenergy use (Foley et al. 2011). Many studies have determined that cereal production needs to be doubled (even tripled) to meet the food demand (World Bank 2008； Godfray et al. 2010).However, the growth of grain yield of many food crops in the global scale is slowing and even stagnating (Ray et al.2012； Grassini et al. 2013). There are large yield variations and gaps across our existing agricultural land, especially in developing counties (Licker et al. 2010； Neumann et al.2010； Ray et al. 2015).

In China, smallholder farmers dominate agricultural production but tend to have poor knowledge of farming technologies and scattered field plots (Zhang et al. 2016).This is particularly the case in the North China Plain (NCP),where the farmers' average yield is only about 41% of its modeled potential with a mean cultivated area of 0.7 hectare per household (Meng et al. 2013). In practice, biophysical,agronomic and socio-economic factors that affect farmers are all attributed to the yield gap, which is the gap between farmer actual yield and attainable or potential yield (Lobell et al. 2009； Liang et al. 2011； Affholder et al. 2013). For instance, Liang et al. (2011) identified poor irrigation and technical service, incorrect nutrient management, and high labor cost as

major causes of the yield gap. Zhao et al.(2016) showed that farmer training was a useful method to achieve sustainable production.

Yield-limiting factors are numerous and complex (Liang et al. 2011； Xiao and Tao 2014； Zhang et al. 2016). In China,grain yield increases strongly rely on increasing nitrogen (N)fertilizer inputs (Cui et al. 2014). Use of synthetic N fertilizer has fed more than half of the world population in the early 20th century (Zhang et al. 2015). In 2010, China, which only accounts for 7% of the global cropland, consumed more than 30% of global fertilizer (FAO 2016). This is almost twice as much as N recovered in crops in China (Chen et al. 2011).Overused fertilizer has caused low nutrient use efficiency(NUE) and has negatively affected the environment through soil acidification (Guo et al. 2010), air pollution (Liu et al.2013), and lakes clogged with algal blooms (Zhang et al.2013). Agronomists have already developed many methods to address the challenge of sustainable crop production(Cui et al. 2008； Chen et al. 2011； Xu et al. 2014). Some studies showed that the N application rate could be reduced by 30-60% without yield losses on experiment fields (Cui et al. 2008； Ju et al. 2009). An integrated soil-crop system management approach (ISSM) developed by Chen et al.(2011) is a model-driven production system. Cui et al.(2008) proposed a precise N management strategy based on soil mineral nitrogen (Nmin； NO3-N+NH4-N, 0-90 cm depth)testing to calculate a recommended of N

application rate.Xu et al. (2014) proposed new fertilizer

recommendations for smallholder farmers with a software program called Nutrient Expert. Those recommendations could significantly increase NUE without yield losses. However, these technologies were well not widely distributed to farmers,partially due to the fact that these proposed technologies were often too complicated for farmers to learn, and the optimum practices are not designed by applying farmers'field data. A simpler and economically cheaper technique is required (Zhang et al. 2016).

The agronomic diagnostic method has been used on many crops to develop sustainable cropping systems. Its principle is to analyze the relationship between yield-limiting factors and yield components (Doré et al. 1997； Makowski et al. 2007； Valantin-Morison and Meynard 2008), to design optimal management practices in a given area (Doré et al.2008).

The objectives of this study were to: i) document the summer maize production situation on smallholder farmers'fields in the NCP； ii) design an improved management practice using famers' production data, and iii) test whether the improved practices could simultaneously increase yield and improve NUE.

2. Materials and methods

2.1. Site description