Soil carbon budget in a single-cropping paddy field with rice straw application and water management based on soil redox potential

Abstract

An ideal state for agroecosystems to mitigate global warming should include both decreasing CO 2 and CH 4 emissions and increasing soil carbon storage. Two-year field experiments were carried out to examine the effects of water management (continuous flooding [CF] and Eh control [EH]) and rice straw management (application [+S] and removal [-S]) on the soil carbon budget in a single-cropping paddy field in Japan. The EH water management based on soil redox potential that the authors have proposed decreased the total CH 4 emission during the rice growing period compared with CF. The +S increased CO 2 emission as soil respiration during the non-flooded fallow period compared with -S, but also increased straw residues in the soil. However, there was little evidence for sequential carbon accumulation in the soil over the year by +S. The resultant annual budget of soil carbon was a loss of 32-103 g C m -2 in the EH+S treatment compared with a loss of 166-188 g C m -2 in the CF-S treatment. Taking into account the global warming potentials, the EH+S treatment also decreased the total CO 2 -equivalent emission compared with the CF-S treatment. Consequently, a combination of appropriate water management and straw application will be an effective option in decreasing both CO 2 -equivalent emission and sustaining soil carbon storage.

Microbial Changes in Selected Operational Descriptors of Dissolved Organic Matters From Various Sources in a Watershed

“…Except for the paddy field soil, the same significant correlation was observed between the SUVA values and the biodegradable carbon percentages for this study (r=0.834; p=0.01). Previous studies have shown that submerged paddy field soils are likely to experience anaerobic condition, which is induced by active microbial activity in underlying water with carbon-rich rice straw presence (Tanji et al 2003;Minamikawa and Sakai 2007). Although more investigations are required for better understanding, the anaerobic condition of paddy fields may possibly lead to the unique DOM characteristics distinguished from other soil-derived DOM.…”

Simultaneous minimization of nitrous oxide and methane emission from rice paddy soils is improbable due to redox potential changes with depth in a greenhouse experiment without plants

“…The experiment was set up in a full 3 × 2 factorial randomized complete block design with 4 replicates. The water management factor had three levels: 1) continuous flooding (CF), in which water depth was maintained at 3 cm above the soil surface for the duration of the experiment, 2) safe alternate wetting and drying (AWD), in which the pots were initially flooded to 3 ± 0.3 cm, then allowed to drain until the 17.5-cm depth soil water potential (SWP) was −10 kPa, then flooded again to 3 cm, etc., and 3) healthy redox (HR), in which the daily redox potential readings were used to determine the irrigation schedule (Minamikawa and Sakai, 2007), keeping the pots flooded to 1 ± 0.3 cm above the surface until the 7.5-cm redox potential reached −150 mV, and then allowing them to drain until the 2-cm redox potential got above + 180 mV, and then re-irrigating to 1 cm, etc. During drainage periods, the percolation rate was about 1 cm d − 1 .…”

Modeling aerobic decomposition of rice straw during the off-rice season in an Andisol paddy soil in a cold temperate region of Japan: Effects of soil temperature and moisture

“…But in the last few decades, an intensive use of chemical fertilizers has led to a decrease in the application of composted manure, and it has become common to leave rice residues in the field directly after rice grain harvest with a combine harvester, in Japan and in other rice-production countries. While the incorporation of rice residues directly into paddy soil has a lot of advantages for CONTACT Weiguo Cheng cheng@tds1.tr.yamagata-u.ac.jp The supplementary material for this article is available online from: http://dx.doi.org/10.1080/00380768.2015.1121116 succeeding plant growth or accumulation of soil carbon (Minamikawa and Sakai 2007), many researchers have also demonstrated the risk of dramatic increases in CH 4 emissions with direct incorporation of rice residues (Yagi et al 1997;Kimura et al 2004). In Japanese rice paddy fields, direct incorporation of rice straw into the soil at rates of 6-9 Mg ha −1 increased the CH 4 emission rate up to 3.5-fold, while the use of rice straw as compost enhanced CH 4 emission only slightly (Yagi and Minami 1990;Watanabe et al 1994).…”