Effect of the long-term application of anaerobically digested residual slurry on methane emissions in a rice paddy field

Abstract

The anaerobic digestion of livestock manure is an environmentally compatible technology used for the production of renewable energy. Anaerobically digested residual slurry has been used worldwide as a liquid fertilizer in both upland and paddy fields. However, a controversial question remains as to whether the application of slurry to rice paddy fields increases methane emissions; although methane is one of the most prevalent greenhouse gases, little is known about the effects of the long-term application of residual slurry on methane emission. In this study, we repeatedly applied slurry to a paddy field for six years at different application rates (10, 15, and 20 g N m −2 based on ammoniumnitrogen content). At the fifth and sixth years of application, we evaluated the effect in terms of methane flux and soil total carbon content. The effect of the long-term application of the slurry (10 g N m −2 ) on grain yield was equivalent to that of chemical fertilizer (10 g N m −2 ). The application of the residual slurry was likely to increase the cumulative methane emissions during rice growing season in both 2006 and 2007. On the other hand, we observed that soil total carbon did not accumulate significantly in the soil. Thus, we cannot rule out the potential risk of additional methane emissions caused by the application of the residuary slurry to paddy fields.

Variable-timing, fixed-rate application of cattle biogas effluent to rice using a leaf color chart: microcosm experiments in Vietnam

“…Although the inputs of P and K from effluent were different from those in U3.25, these comparisons suggest that urea was more effective N-fertilizer form in this study. This result is consistent with those of Nishikawa et al (2012) and Tanaka et al (2017), so the calculation of N applied from the biogas effluent that we used should be based on NH 4 -N instead of total N. Our study did not reveal significant differences in grain yield among the five E-LCC treatments (Table 3), mainly on account of the high spatial variation, as discussed above. However, the positive linear relationship between grain yield and LCC value (or SPAD value; Figure 3) suggests that a higher LCC threshold than we used would have been favorable in terms of grain production under the current microcosm conditions.…”

Methanotrophic Inoculation Reduces Methane Emissions from Rice Cultivation Supplied with Pig-Livestock Biogas Digestive Effluent

“…This study found that the total CH 4 emission varied from 21.3 to 30.6 g CH 4 m −2 , which was in line with previous reports using cascade effluent for rice fields [17,[19][20][21]24] (Table 4) as well as referring to the VMD's rice fields [34,[54][55][56]. However, the CH 4 emission varied between study sites and livestock's BDE.…”

“…Moreover, reusing BDE for rice paddy fields can improve soil fertility by enriching organic matter, amino acids, bioactive substances, and various nutrients [9,14,15]. In fact, the cascade utilization of digestate for rice cultivation has recently been noticed in terms of its nutrient availability and yield-unsacrificed feasibility [16][17][18]. However, a major concern in employing BDE for rice crops has been remarked as potential risks of higher CH 4 flux.…”

“…Higher CH 4 emissions from fields applied with BDE could be attributable to the expansion of organic matter, especially the intensification of soil labile or dissolved organic carbon [1,22,23]. Indeed, BDE/slurry remains ~0.4-1.8 g carbon per litter [17,20]. Therefore, the BDE irrigation fuels anaerobic carbon mineralization, which is a substrate preferred by methanogens (CH 4 -producing archaea), resulting in higher CH 4 emissions [1].…”