Interaction of lime application and straw retention on ammonia emissions from a double-cropped rice field

Highlights

• Liming alone increased NH₃ emissions and NH₃ emission factors (EFs) in a double-cropped rice field.

• Straw retention alone promoted NH₃ emissions in the early rice growth season but reduced them in the late rice growth season.

• Liming interacted with straw retention to increase NH₃ emissions and EFs in the early rice growth season.

• Liming had no significant interactions with straw retention on NH₃ emissions and EFs in the late rice growth season.

Abstract

Ammonia (NH₃) emissions are an important pathway of nitrogen (N) losses in rice paddies. Lime application and straw retention are common practices to enhance soil fertility in acidic soils. However, the interaction of lime and straw application on NH₃ emissions from paddies remain unclear. Here, a factorial experiment was employed to examine the interactive effects of slaked lime (i.e., Ca(OH)₂) and straw retention on NH₃ emissions and NH₃ emission factors (EFs) in a double-cropped rice field. The results showed that compared to unlimed treatments, liming promoted NH₃ emissions and EFs by 98.6% and 90.2% in the early rice growth season, respectively, with increases of 16.3% and 15.7% in the late rice growth season. Relative to straw removal, straw retention increased NH₃ emissions by 52.8% in the early rice growth season but did not alter EFs, while reducing NH₃ emissions by 9.9% and EFs by 25.7% in the late rice growth season. Liming interacted with straw retention to increase NH₃ emissions and EFs in the early rice growth season. Under straw retention, liming promoted NH₃ emissions by 147.7% and EFs by 148.3%, whereas liming raised NH₃ emissions and EFs only by 45.3% and 45.5% under straw removal, respectively. Liming had no significant interactions with straw retention on NH₃ emissions and EFs in the late rice growth season. It is likely that the decomposition extent of straw can alter the response of NH₃ emissions to liming. Thus, NH₃ emission inventories should take into account the interaction of liming and straw retention and its dependence on rice growth seasons in double-cropped rice systems with acidic soils.

Introduction

Ammonia (NH₃) is an essential precursor to the formation of atmospheric secondary aerosols that can significantly impact human health (Ma et al., 2021a). In addition, emitted NH₃ returns to water and soil surfaces via nitrogen (N) deposition, thereby aggravating groundwater contamination, surface water eutrophication, soil acidification, and biological diversity loss (Pan et al., 2016). Agricultural activities account for 80% of total NH₃ emissions from anthropogenic sources worldwide (Behera et al., 2013). Rice (Oryza sativa L.) paddies represent a notable emission source of NH₃ (Wang et al., 2018), accounting for 24% of the global NH₃ emissions from croplands (Ma et al., 2021b). As an important rice-producing system in China, double rice cultivation (i.e., rice planted twice annually) represents up to approximately 35% of planting area and 30% of rice production (NBS, 2019). However, the double-cropped rice system is mostly practiced in subtropical China, where soil acidification and soil degradation are the critical constraints to the sustainability of rice production (Liao et al., 2018, Tang et al., 2022).

Limes are generally recommended to mitigate soil acidity and increase grain yield in rice paddies (e.g., Shamshuddin et al., 2017; Liao et al., 2021; Zhang et al., 2022). However, liming alone has a limited role in enhancing soil fertility such as soil organic carbon (C) and N (Liao et al., 2018). In contrast, straw retention can improve soil fertility in rice paddies due to the input of large amounts of organic matter and nutrients (e.g., Ding et al., 2018; Guo et al., 2021). However, increasing evidence indicates that straw incorporation can only reduce the rate of soil acidification relative to inorganic fertilization alone rather than markedly raising soil pH like limes can in acidic paddies (Liao et al., 2018, Hao et al., 2022, Tang et al., 2022). Thus, combining lime and straw application has been advocated to simultaneously enhance soil fertility and ameliorate soil acidification in order to promote rice production in acidic paddy soils (Jiang et al., 2018, Liao et al., 2018). In addition, liming combined with straw incorporation could improve soil aggregation, thereby promoting root growth (Haynes and Naidu, 1998). However, while most of these previous studies have main focused on the impacts of combining liming and straw retention on soil quality and grain yield, little is known regarding the interaction of lime application and straw retention specifically on NH₃ emissions from double-cropped rice fields.

It is well known that NH₃ emissions are largely derived from the application of mineral N fertilizers in rice paddies (Lian et al., 2018, Zhong et al., 2021, Wang et al., 2022a). Meanwhile, NH₃ emissions are affected by soil environmental variables (e.g., soil pH, soil organic N and C) (Jiang et al., 2017, Wang et al., 2021). Therefore, lime application and straw retention can affect NH₃ emissions in rice paddies (Huang et al., 2016). For instance, Smith et al. (2009) demonstrated that for every 0.1 unit increase in soil pH through liming, NH₃ emissions increased by about 3.3 kg ha⁻¹. In addition, straw retention has been reported to alleviate (Cao et al., 2018), promote (Xu et al., 2017, Xia et al., 2018), or have no impact (Li et al., 2021, Xu et al., 2022) on NH₃ emissions in paddies. The differential responses of NH₃ emissions to straw retention are likely due to the variation in C/N ratios of crop residue that regulate soil microbial activity and thus affect the dynamics of soil N immobilization-mineralization (Pan et al., 2017, Liu et al., 2021). Previous findings have indicated that applying lime promotes the activities of soil enzymes associated with N and C cycling, thereby stimulating the decomposition of crop residue and N mineralization (Heyburn et al., 2017, Liao et al., 2018). Thus, we hypothesized that applying limes may promote N release in straw and thus increase NH₃ emissions under straw retention in double-cropped rice fields with acidic soils. Although many studies have examined the individual impact of lime application or straw retention on NH₃ emissions in rice paddies, no study to our knowledge has explored their interactive effects on NH₃ emissions in the double-cropped rice system (Besen et al., 2022, Xu et al., 2022). To test this hypothesis, a factorial designed experiment with lime application and straw retention was used to explore the impacts of their interaction on NH₃ emissions in a double-cropped rice field.