Effect of long term fertilization management strategies on methane emissions and rice yield

https://doi.org/10.1016/j.scitotenv.2020.138261Get rights and content

Highlights

  • Optimum fertilization had no significant effect on grain yield and CH4 emissions.

  • Seasonal CH4 emissions were significantly negatively correlated with grain yield.

  • Soil available K, P and mcrA gene were the key variables in mineral fertilized plots.

  • CH4 emissions in organic fertilized plots were mainly related to soil fertility.

Abstract

Optimum fertilization is an efficient method to maintain rice yield and reduce N-losses. It is essential though to evaluate methane emissions from paddy fields, to further understand its impact on greenhouse gas budget. Therefore, a field experiment was conducted to investigate the effect of long-term optimum fertilization on CH4 emissions and rice yield. We collected data in the 7th and 8th year from a field experiment initiated in 2010. Four optimum fertilization strategies, reduced N-fertilizer and zero-P treatment (RNP, 200 kg N/ha), sulfur-coated urea combined with uncoated urea treatment (SCU, 200 kg N/ha), organic fertilizer combined chemical fertilizer treatment (OCN, 200 kg N/ha), organic fertilizer treatment (OF, 200 kg N/ha); and two controls, the farmers' N management (FN, 270 kg N/ha) and zero-N treatment (N0), were employed. The results showed the rice yields achieved for the optimum fertilization treatments (RNP, SCU, OCN, and OF) were similar with those for the FN. No significant differences in CH4 emissions among all treatments. Cumulative seasonal CH4 emissions were negatively correlated with grain yield (P < 0.05). In the RNP and SCU treatments, soil available K, mcrA gene and available P were the key variables affecting CH4 emissions; soil available K, available P and SOC contents were the key emissions factors for OCN and OF treatments. The SCU achieved the highest rice yield and lowest CH4 emission intensity among optimum fertilization treatments. These results suggest that long-term application of sulfur-coated urea combined with uncoated urea can maintain rice yield and reduce methane emissions from rice paddies.

Introduction

Rice is one of the most vital crops in the global cereal production nexus, providing with >20% of the daily metabolic energy for >3.5 billion people (Seck et al., 2012). Paddy fields is an important methane (CH4) emission source accounting for ~11% of global methane emissions (IPCC, 2013; Carlson et al., 2016), the second major greenhouse gas (GHG) after carbon dioxide (CO2). Methane emissions from paddy fields is often stimulated or inhibited by microbial activity (Mer and Roger, 2001; Yuan et al., 2019), organic amendment (Yan et al., 2005; Zhang et al., 2018), nutrient addition and subsequent changes in soil fertility (Linquist et al., 2012a; Linquist et al., 2012b), and finally, root exudation (Maurer et al., 2018). The differences in fertilization strategies (type and their application rate) inevitably lead to differences in the soil properties that affect the microbial communities developed over time. Thus, it is essential to evaluate the effect of fertilization management on the CH4 emissions from paddy fields.

Previous studies noted that the methane emissions from paddy fields vary depending on fertilizer type as well as the application rate. With regards the chemical fertilizers, studies have indicated that lower N input increases CH4 emissions from paddy fields due to the increased available carbon (typical electron acceptor for the methanogenic population) (Banger et al., 2012; Linquist et al., 2012b). On the other hand, the effect of phosphorus-based fertilization on CH4 emissions is typically inconsistent due to changes in the methanogenic abundance subjected to soil properties and plant growth (Rath et al., 2005; Sheng et al., 2016; Maurer et al., 2018). In the case of organic amendments, it is well known that such additives increase CH4 emissions from rice paddies; the rate and type of application though has a varying effects (Khosa et al., 2010; Bhattacharyya et al., 2013). Specifically, Zhang et al. (2018) pointed that by employing manure additives the mcrA gene (methanogenic) abundance increases, observation aligned with the status of dissolved organic C, total P, and available P and K in the soil. Recently, slow/controlled-release fertilizers have been widely applied in paddy field (Hou et al., 2019). It has been proved that controlled-release fertilizers have the potential to reduce CH4 emissions from paddy fields their mechanism though is yet unclear (Ji et al., 2014; Zhou et al., 2014; Anitha and Bindu, 2016; Guo et al., 2019). Among these, sulfur-coated urea (SCU) fertilizers, not only has a slow N-release property but also provides with sulfur for the paddy fields; this type of fertilizers is typically used in the broad area of central-eastern China. It has been indicated that the sulfur addition helps to mitigate methane emissions from wetland sources as such components act as electron sink that could scavenge acetate and hydrogen to prevent methanogenesis (Gauci et al., 2004). The above observations demonstrate that the supplement of specific compounds that are often present in different fertilizers, at specific application rates, among other factors render the prediction of CH4 emissions from paddy fields very complex.

Within the last decade, rice is cultivated on a total harvested area of approximately 158 million hectares worldwide (Seck et al., 2012). Approximately 90% of the rice in the world is grown in Asia, with China as the lead producer (FAO, 2016). In China, rice-wheat rotation is gradually replaced by rice-fallow rotation as the main planting pattern in Tai-lake region. This is mainly driven by the recent policy for the protection of Tai-lake as well as the overall benefits of the new method. To reduce the N losses from paddy fields, optimum fertilization methods, such as reduced N application and omitting-P fertilizers, sulfur-coated urea combined with urea, organic fertilizer applied alone or combined with urea, etc., are often employed (Xue et al., 2014). The variety in the supplementation of compounds present in different fertilizers, combined with changes in the planting pattern, may alter soil fertility and subsequently shift the microbial community, especially after prolonged exposure of soils in such supplements and changes (Zhang et al., 2009; Bhattacharyya et al., 2013). Combined with the above observations, the questions that emerge are (1) what is the composite effect of both reduced N input and omitting P input on methane emissions when the effect of low-P on methane emissions is inconsistent and lower N input increases the CH4 emissions; (2) what is the effect of continuous compost application on methane emissions from paddy fields in rice-fallow rotation, and whether the effect is consistent with previous studies; (3) could the long term application of SCU to soil reduce the methane emissions through the input of sulfur?

Methane emissions from paddy fields is often stimulated or inhibited by microbial activity, organic amendment, nutrient addition and subsequent changes in soil fertility. To answer the above questions and clarify the key variables affecting methane emissions, this study evaluates the differences in methane emissions from paddy fields under different continuous fertilization management practices and investigates the links between soil fertility and microbial abundance of the two key consortia (methanogens, methanotrophs). We expect the results assist in clarifying the differences in methane emissions under long term optimum fertilization strategies so farmers and farming engineers/agronomists can master the influential factors leading to greenhouse gas pollution so they can propose of more sustainable fertilization strategies to tackle global warming.

Section snippets

Experimental site

The field data collection was performed in 2016 and 2017 at Yinghu village, Wangting town, Suzhou city, China (120°24′58″E, 31°24′35″N), an area where the primary cropping regime is annual paddy-upland rotation. The average daily temperature during the rice growing season was 25.69 °C in 2016 and 25.32 °C in 2017. The meteorological data during the measurement season are shown in Fig. 1.

Experimental design

The field experiment initiated in June 2010 and continued since the rice-growing season of that year. The

CH4 flux

The seasonal variation of CH4 flux from the trialed paddy fields is shown on Fig. 2. The results show that the variability in methane flux from the continuous fertilization manage plots was similar during the rice growing season and only differed temporally mainly in amplitude. The methane flux rate from the paddy fields for all treatments peaked during the first 40 and 30 days for the 2016 and 2017 plantations respectively. Similarly, the CH4 flux peaked at 30 days (tillering stage) for the

Discussion

Water content in rice fields is one of the critical factors affecting/regulating methane emissions (Yan et al., 2005; Sistani et al., 2011). During experimentation, methane emissions from paddy fields mainly generated during the early plantation days (30–40), the CH4 flux peaked at 30 days in 2016 and 11–13 days in 2017 (Fig. 2). Floodwater conditions at paddy fields before mid-season, after transplanting, confirms the relationship between emissions and water content (Peyron et al., 2016).

Conclusions

Prolonged, optimum fertilization (for over 8 years) could promote sustainability in rice cultivation (rice-fallow rotation) ensuring good rice yield combined with relatively low or controlled CH4 emissions. The cumulative seasonal CH4 emissions released from all plots fertilized with different strategies (FN, RNP, SCU, OCN, OF) showed insignificant differences; similarly for the yields achieved. Overall, cumulative seasonal CH4 emissions were negatively correlated with grain yield. For the

CRediT authorship contribution statement

Pengfu Hou: Investigation, Formal analysis, Writing - review & editing. Yingliang Yu: Investigation. Lixiang Xue: Investigation. Evangelos Petropoulos: Writing - review & editing. Shiying He: Data curation. Yushu Zhang: Formal analysis. Arjun Pandey: Writing - review & editing. Lihong Xue: Writing - review & editing. Linzhang Yang: Supervision. Deli Chen: Writing - review & editing.

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgments

This work was supported by the National Key Research and Development Program, Ministry of Science and Technology, China [2017YFD0300104]; the National Natural Science Foundation of China [41601319]; the National Major Project of Science and Technology Ministry of China [2017ZX07202-004-03]; and Jiangsu Agriculture Science and Technology Independent Innovation Fund [CX(19)1007]. The authors would like to thank Prof. Yu Jiang from Nanjing Agricultural University and Dr. Jun Zhang from Chinese

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