Elsevier

Field Crops Research

Volume 266, 1 June 2021, 108146
Field Crops Research

Meta-analysis of green manure effects on soil properties and crop yield in northern China

https://doi.org/10.1016/j.fcr.2021.108146Get rights and content

Highlights

  • Evaluation of green manure application effect by meta-analysis.

  • Green manure can significantly improve soil nutrient content.

  • Green manures’ type affects succeeding crops yield.

Abstract

The application of green manure is a traditional and valuable practice for agroecosystem management. In northern China, the effects of green manure on production of the region’s major crops have been extensively investigated, but the inconsistent conclusions that these case studies have yielded cannot provide effective guidance for practical local agricultural production. Here, we conducted a meta-analysis to generate a comprehensive evaluation of the effects of green manure on soil properties and crop yield in this region. Our results shown that green manure improves soil quality effectively, decreasing soil bulk density by ∼ 5.6 %, increasing microbial biomass carbon by 28 %, and improving the activities of soil enzymes by 14 % ∼ 39 %. Among the different types of green manure, legume green manure more markedly increased both nitrate and hydrolysable nitrogen, while non-legume green manure more markedly increased available potassium. Soil gravimetric water content was decreased under green manure treatment. Maize yield was significantly increased under green manure by 11 % on the whole, while effects of green manure on wheat and potato were inconsistent. In summary, the application of green manure in northern China can improve soil quality significantly, and proper green manure use can improve cash crop yields.

Introduction

The food production industry is under increasing pressure with the rapid growth of the world’s population. How to produce more food on our limited arable land is one of the greatest challenges that agriculture will face in the future (Ibarrola-Rivas et al., 2017; Tiwari et al., 2018). Soil is the basis of agricultural production. The intensive and improper use of land that often results from the pressure of increased food demand leads to the degradation of farmland soil. For example, long-term monocropping causes an imbalance of soil nutrients and the accumulation of harmful elements (Ernst et al., 2018; Qin et al., 2017;Trasar-Cepeda et al., 2008). The excessive use of chemical fertilizers and pesticides in agricultural production has also had a severe negative impact on soil quality (Chhipa, 2017; Ding et al., 2017;Ren et al., 2019). Therefore, how to coordinate food production and ensure the sustainable use of farmland is one of the most urgent issues agriculture is facing today, and sustainable agricultural management techniques are especially needed.

The application of green manure (green manure) is an old agricultural management practice that has re-attracted people’s attention in recent years because of its environmentally friendly properties. A large number of studies have proved the positive effects of green manure application on improving agricultural production in different areas (Couedel et al., 2018;Valkama et al., 2015; Yang et al., 2018). The beneficial effects can be summarized as follows: 1) preventing soil erosion and decreasing the runoff from farmland in the fallow period (Almagro et al., 2016; Sharratt et al., 2018; Singh et al., 2017); 2) reducing soil bulk density and increasing the content of soil organic matter, soil nitrogen, soil phosphorus, soil potassium and other nutrients, and thus reducing the use of chemical fertilizers (Chaudhary et al., 2017; Damon et al., 2014; Li et al., 2015a, 2015b; Thorup‐Kristensen et al., 2003); 3) improving soil biodiversity and enzyme activity, and accelerating soil nutrient transformation (Gao et al., 2016; Kataoka et al., 2017); 4) enabling control of weeds, pests and diseases, which in turn cuts down the use of pesticides (Alvarez-Iglesias et al., 2018; Masilionyte et al., 2017; Puig et al., 2019); 5) increasing crop yields and farmers' profits (Astier et al., 2006; Cordoa et al., 2018; Toom et al., 2019).

In China, the use of green manure in agriculture has a long history but has diminished significantly since the 1980s with the increased use of chemical fertilizers in agricultural production (Cao and Huang, 2009). In recent years, in response to the rapid degradation of farmland soil and the high cost of chemical fertilizers, the use of green manure has been re-evaluated in contemporary agricultural production, and a large number of studies on the application of green manure have been performed (e.g. Xie et al., 2019; Yao et al., 2019; Zhang et al., 2016a, 2016b, 2016c). In southern China, positive effects of green manure on soil improvement and crop yields have been confirmed through a large number of field experiments, which provides useful guidance for practical agricultural production in this area (Gao et al., 2016; Ding et al., 2018; Xie et al., 2017).

As China’s main grain-producing region, the northern region plays an important role in China’s food security (Kuang et al., 2015; Sun et al., 2010). Although many studies on the application of green manure have been conducted in this area, these studies have reached contradictory conclusions (He et al., 2016; Xue et al., 2017; Yang et al., 2014; Zhang et al., 2016a). Compared with southern China, northern China’s climate, crop species and planting systems are more complex, especially due to the region’s limited precipitation, which leads to competition between crops and green manure for the available water resources. On the other hand, most of these isolated case studies have assessed the effect of green manure in terms of a single aspect. Therefore, no single study can provide adequate scientific guidance for the large-scale application of green manure in northern China. In view of this, the agricultural industry needs an integrated analysis of the existing independent research data and a comprehensive evaluation of the effects of green manure on crop production in this region.

Meta-analysis is a comprehensive method of analyzing a series of independent studies. The effect size of meta-analysis enables researchers to quantitatively analyze the effects of treatments applied in different studies (Gurevitch and Hedges, 1999). Due to its rigorous analytical process and quantitative results, meta-analysis has been widely used in agricultural research. As China’s main grain-producing region, northern China has unique planting systems as well as distinctive climatic characteristics; accordingly, any conclusions drawn from integration analyses of other regions may not be applicable to this area. Thus it is necessary to conduct a comprehensive analysis specific to this area. In the current study, we performed a meta-analysis on the effects of green manure on soil physical and chemical properties, soil moisture and subsequent crop yields in northern China. Our report presents comprehensive scientific recommendations for the application of green manure in the planting systems of this region.

Section snippets

Study area

Northern China is located between 73–136 °E longitude and 31–54 °N latitude, with a total area of approximately 5.1 × 10^6 km2 (Zhen et al., 2010). It includes the following provinces: Shaanxi, Gansu, Qinghai, Ningxia, Xinjiang, Beijing, Tianjin, Hebei, Shanxi, Inner Mongolia, Heilongjiang, Jilin, Liaoning and Shandong (Fig. 1). Dominated by a continental monsoon climate, the annual mean temperatures of this region range from −5 to 15 °C, and mean annual precipitation gradually decreases from

Soil bulk density and pH

Compared with the fallow control, green manure treatment decreased soil bulk density significantly, by 5.6 % in the 0–20 cm soil layer and by 4.0 % in the > 20 cm layer. Meanwhile, soil pH showed no significant changes as a result of the introduction of green manure in either the 0–20 cm or the > 20 cm soil layer. (Fig. 2).

Soil biological characteristics

Application of green manure had a significant positive effect on microbial biomass carbon levels and soil enzyme activities. As shown in Fig. 3, soil microbial biomass carbon

Discussion

In practical agricultural production in northern China, farmland is commonly left bare from the harvest of the previous crop to the sowing of the next crop, which provides the spatial and temporal conditions for the application of green manure. Our study found that the application of green manure in this region significantly improved soil fertility and soil enzyme activities (Fig. 3, Fig. 4, Fig. 5, Table 1). These improvements in turn had variable effects on crop yield depending on crop and

Conclusions

In northern China, green manure application during the fallow period can significantly improve soil quality in both the 0–20 cm and the > 20 cm soil layer. Green manure can reduce soil bulk density, enhance soil biological activity, and significantly increase the contents of N, P and K. For the consumption of soil water during its growth period, green manure can lead to the decrease of 0–2 m soil water content. The effect of green manure application on subsequent crops yield varies according to

Declaration of Competing Interest

The authors report no declarations of interest.

Acknowledgements

We appreciate all of the researchers whose data were used in this meta-analysis. This work was supported by the National Key Research and Development Program of China (2018YFD1001003), the National Key Technology R&D Program (2015BAD22B01), and the 111 project of the Chinese Education Ministry (B12007).

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