Effect of Paddy-Upland Rotation System on the Net Greenhouse Gas Balance as the Sum of Methane and Nitrous Oxide Emissions and Soil Carbon Storage: A Case in Western Japan

Hiroyuki Hasukawa,Yumi Inoda,Yasuhito Shirato,Junta Yanai,Noriko Oura,Shigeto Sudo,Tomohito Sano,Satoshi Toritsuka

doi:10.3390/agriculture11010052

Abstract

To investigate the effect of paddy-upland (PU) rotation system on greenhouse gas emissions, methane (CH4) and nitrous oxide (N2O) emissions were monitored for three years for a PU rotation field (four cultivations (wheat-soybean-rice-rice) over three years) and continuous paddy (CP) field on alluvial soil in western Japan. Soil carbon storage was also calculated using an improved Rothamsted Carbon (RothC) model. The net greenhouse gas balance was finally evaluated as the sum of CO2eq of the CH4, N2O and changes in soil carbon storage. The average CH4 emissions were significantly lower and the average N2O emissions were significantly higher in the PU field than those in the CP field (p < 0.01). On CO2 equivalent basis, CH4 emissions were much higher than N2O emission. In total, the average CO2eq emissions of CH4 plus N2O in the PU field (1.81 Mg CO2 ha−1 year−1) were significantly lower than those in the CP field (7.42 Mg CO2 ha−1 year−1) (p < 0.01). The RothC model revealed that the changes in soil carbon storage corresponded to CO2eq emissions of 0.57 and 0.09 Mg CO2 ha−1 year−1 in the both fields, respectively. Consequently, the net greenhouse gas balance in the PU and CP fields were estimated to be 2.38 and 7.51 Mg CO2 ha−1 year−1, respectively, suggesting a 68% reduction in the PU system. In conclusion, PU rotation system can be regarded as one type of the climate-smart soil management.

Highlights

In recent years, the average temperature has risen worldwide and global warming has been pointed out, and it is necessary to drastically and sustainably reduce greenhouse gases (GHG) emissions in order to curb climate change [1]
The CH4 and N2 O flux in the three years are shown in Figure 1a,b, respectively, and seasonal changes in precipitation and water-filled pore space (WFPS), and Eh in the three years of the experiment are shown in Figure 1c,d, respectively
The CH4 and N2O flux in the three years are shown in Figure 1a,b, respectively, and seasonal changes in precipitation and water-filled pore space (WFPS), and Eh in the three years of the experiment are shown in Figure 1c,d, respectively

Summary

Introduction

The average temperature has risen worldwide and global warming has been pointed out, and it is necessary to drastically and sustainably reduce greenhouse gases (GHG) emissions in order to curb climate change [1]. It has been pointed out that the greenhouse gases CH4 and N2 O emitted from agricultural lands have increased drastically over the past half century due to the expansion of paddy field cultivation worldwide and the increase in nitrogen fertilizer application [2,3]. As one of the techniques for reducing CH4 emissions from paddy fields, effectiveness of water management such as intermittent irrigation and extension of the mid-summer drainage period have been clarified [11,12,13]. In this context, rice (Oryza sativa) cultivation systems with extended non-flooded period are expected to be effective for reducing CH4 emissions

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Conclusion