Elsevier

Chemosphere

Volume 242, March 2020, 125247
Chemosphere

Responses of ammonia volatilization from rice paddy soil to application of wood vinegar alone or combined with biochar

https://doi.org/10.1016/j.chemosphere.2019.125247Get rights and content

Highlights

  • Acidic wood vinegar (WV) and alkaline biochar (BC) were co-applied to rice paddy soil.

  • WV + BC reduced NH3 volatilization while WV alone increased that.

  • Yield-scale NH3 volatilization of WV + BC was reduced by 13.6%.

  • Soil of WV + BC had lower pH and urease activity, but higher NH4+ content.

  • WV + BC is recommended to achieve higher rice yield and lower NH3 volatilization.

Abstract

Wood vinegar (WV) was applied alone or combined with biochar (BC) to observe their efficiency on suppressing the ammonia (NH3) volatilization from rice paddy soil. Five treatments, i.e., control (240 kg N ha−1 applied in urea), WV-5 and WV-10 (240 kg N ha−1 plus 5 and 10 t WV ha−1, respectively), and their counterparts WV-5-BC and WV-10-BC (WV-5 and WV-10 plus 7 t BC ha−1), were evaluated by a soil columns experiment. The N fertilizer was split applied as basal and two supplementary fertilizations (named BF, SF1 and SF2, respectively). The results showed that WV-5 treatment increased rice grain yield up to 11.2% compared to the control. Compared with the control, four WV-amended treatments, exhibited lower pH values of the floodwater (7.94–8.18 vs 8.47 and 7.85–7.91 vs 7.98) and the topsoil (6.52–6.76 vs 6.82 and 6.82–6.92 vs 6.99) during the BF and SF1 periods. Both WV-5 and WV-10 increased the NH4+-N contents of topsoil by 10.9–17.8% and 16.1–36.2% after BF and SF1, respectively, than control treatment. Additionally, the floodwater of the WV-amended treatments had higher NH4+-N concentration than control during the first three days after N fertilization, which can be attributed to the stimulating effect of WV on soil urease enzyme activity. WV did not effectively reduce NH3 volatilization as hypothesized. Interestingly, four WV-amended had relatively reduced the yield-scale NH3 volatilization by 13.6% than the control. It is suggested that WV needs to be applied with BC at a moderate rate to achieve optimum rice yield and mitigate NH3 volatilization.

Introduction

The artificial-source emission of ammonia (NH3) mainly comes from nitrogen (N) fertilization and the breeding of livestock and poultry (Pan et al., 2016). In particular, NH3 volatilization from farm land is estimated to be 11.8 Tg per year in East, Southeast and South Asia (Yan et al., 2003). Recently, He et al. (2018) estimated that approximately 13.2–47.0% of applied N fertilizer in paddy fields is lost via NH3 volatilization based on published data. NH3 volatilization not only lowers the N usage efficiency but also causes hydrographic and atmospheric pollution (Wang et al., 2011; Behera et al., 2013). Therefore, it is of great significance to reduce NH3 volatilization from paddy fields through comprehensive technical means which includes sustainable agricultural practice (Pan et al., 2016).

At present, biochar as a major carbon source has been reported as a soil additive that can immobilize of organic pollutants and potentially toxic elements (Qin et al., 2018; Xia et al., 2019), and enhance soil fertility (Feng et al., 2018; Sun et al., 2019a) through their unique surface properties. However, biochar often has alkaline characteristics (Wu et al., 2019; Yang et al., 2019), which may increase the pH of the soil-water system (Sha et al., 2019; Sun et al., 2017). Based on our previous studies, the elevated pH could increase NH3 volatilization in paddy, reclaimed saline soils or urban compacted soils when biochar is overused at a rate of approximately 3 wt% (Feng et al., 2017; Sun et al., 2017, 2019b). To reduce NH3 volatilization, it is crucial to regulate the pH of the soil-water system in paddy fields during the critical fertilization period. Humic acid application and duckweed inoculation could reduce the pH of surface water in paddy fields (Li et al., 2009; Shaaban et al., 2013; Sun et al., 2019c). Meanwhile, the ammonium (NH4+) adsorption capacity of biochar also plays a major role due to the high specific surface area of biochar (Mandal et al., 2018), which influence the consequent NH3 volatilization.

Wood vinegar (WV) has attracted our interest due to its acidic (pH 3–7) and nutrient-rich characteristics (the presence of abundant N, P and K) (Fagernäs et al., 2015; Zheng et al., 2018). WV, also known as pyroligneous acid, is a byproduct of gas condensation products formed during biochar production (Grewal et al., 2018). WV usually has a high yield, which can reach 7.26% of the total biomass as reported (Mopoung and Vijitr, 2015). In recent years, research on WV has focused on bacteriostatic agents, antioxidants, plant growth regulators, and soil additives in the fields of medicine, food, agriculture and the environment (Li et al., 2019; Zhang et al., 2019). It has been reported that the application of WV can promote the growth of plants (Simma et al., 2017), by improving soil nutrient conditions (Lashari et al., 2013; Polthanee et al., 2015). Moreover, proper application of WV was reported to have a positive effect in terms of reducing CH4 and N2O emissions from rice paddy fields (Sun et al., 2018).

WV is typically acidic, while biochar is usually alkaline (Sha et al., 2019). Therefore, when biochar and WV are applied together to farmland, an acid-base balance can be achieved to a certain extent, and thus the disturbance to the soil-water system pH could be regulated. Moreover, the porous properties of biochar will allow the absorption of certain organic compounds in WV (Paustian et al., 2016). Chen et al. (2010) and Wang et al. (2018a) reported that WV combined with biochar in manure composting could reduce NH3 emissions significantly. However, research on the combined application of WV and biochar to rice paddy fields are highly limited (Sun et al., 2018), and only a few reports have referred to the effect of WV on NH3 volatilization in paddy fields, which needs to be investigated by further research. As an effective soil amendment, WV may produce significant economic and environmental benefits if it can be properly applied in the agricultural production process (Lashari et al., 2013).

The effect mechanisms of WV combined with biochar on NH3 volatilization in paddy fields may be mainly as follows: 1) NH3 volatilization will be affected through short-term pH and NH4+ changes of the soil-water system. 2) Soil microbial activity might be affected, especially urease activity, which will alter NH3 volatilization. Based on the above hypotheses, the objectives of this study are as follows: 1) to investigate the effects of WV and biochar on NH3 volatilization from rice paddy soil and 2) to explore the mechanisms through which the combined application of WV and biochar affect NH3 volatilization. This study will provide theoretical and data support for the application of WV in paddy fields to mitigate NH3 volatilization and it will meanwhile expand the knowledge base for large-scale application of WV and biochar in future.

Section snippets

Soil column experiment and fertilization management

In this experiment, a column (constructed with PVC materials with 30 cm in diameter and 50 cm in height) experimental system was used during the whole rice growth cycle in Nanjing, Jiangsu Province, China. The rice variety used in this experiment was Wuyunjing 23, and the tested soil was classified as a Hydragric Anthrosol, which was collected from 0 to 20 cm topsoil of the rice field in Zhoutie Town, Yixing City, Jiangsu Province. The soil was air dried naturally and thereafter repacked into

Rice grain yield

The control treatment produced 11.6 t ha−1 of rice grain, and the four other treatments yielded 10.6–12.9 t ha−1. The data in Fig. 1 show that whether WV application alone at two rates or with biochar had no significant (P > 0.05) influence on rice production compared to the control. The WV-5 treatment yielded the highest relative rice production of 12.9 t ha−1. It is well established that WV can increase crop productivity by regulating soil pH and nutrients condition (Lashari et al., 2013;

Conclusions

A soil column experiment was conducted to evaluate the impact of WV and the combined application of WV and BC on NH3 volatilization from N-fertilized rice paddy soil considering various aspects, including soil-water pH, NH4+-N contents and urease enzyme activity. The pH values of both floodwater and topsoil decreased after WV addition alone or with BC. In comparison to the control, the two WV-only treatments increased the NH4+-N concentrations of the topsoil and floodwater as a result of the

Supplementary Information

Detailed information about WV used in this study, and the impacts of WV applied alone or with BC on rice plant growth are presented in Supplementary Information.

Funding

This research is funded by the National Key Research and Development Program of China (2018YFD0800206, 2018YFD0800204), the National Natural Science Foundation of China (31972518, 41877090), and the Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD).

Declaration of competing interest

The authors declare no conflict of interest.

Acknowledgments

The contribution of Ms. Wang Y. from Jiangsu Academy of Agricultural Science will be highly appreciated. Feng Y. thanks the financially support from Jiangsu Academy of Agricultural Science to study as a post-doctoral fellow in the University of Massachusetts, Amherst.

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