Effect of Flooding Management on Carbon Content of Soil and Plant After Cessation of Paddy Rice Cultivation

Abstract

Shimoda -Sakurai: Effect of flooding management on carbon content of soil and plant after cessation of paddy rice cultivation - Abstract. We measured soil carbon (C) and its stable isotopic composition in paddy fields that had received different fallow treatments for 6 years to investigate how management practices influenced the response of soil C. The experiment compared 4 fallow treatments in neighboring fields: mowing twice a year and no tillage (MN), mowing twice a year and puddling once a year (MP), and flooding to 5 or 15 cm and puddling (WP5, WP15) to prevent succession to wasteland and thus permit future cultivation. MN had the potential to increase soil C more than MP5 through larger root and shoot buildup. However, the total soil C content to a depth of 30 cm was significantly higher in WP5 (13.7 Mg C ha -1 ) than in MN (11.8 Mg C ha -1 ). The dry-fallow management increased plant growth while reducing soil C. The large root dry weight in MN and MP could have increased soil C through high root turnover, whereas land use change from flooding to dry-land masked the abundant C input. After cultivation stops, flooding plays a significant role in preventing root growth and C sequestration in fallow paddy fields.

Land Use Alters the Plant-Derived Carbon and Nitrogen Pools in Terraced Rice Paddies in a Mountain Village

“…Abandoned upper terraced paddies are exposed to the atmosphere, while the lower slope position usually maintains high groundwater levels [27]. The gentle C increase after land use was caused by our mountainous fields at the upper part of terraced paddies, supporting the previous studies [25,26].…”

“…Abandoned upper terraced paddies are exposed to the atmosphere, while the lower slope position usually maintains high groundwater levels [27]. The gentle C increase after land use was caused by our mountainous fields at the upper part of terraced paddies, supporting the previous studies [25,26] 20-30 cm after abandonment. This may be a consequence of the length of time it takes for C and N to move down through the soil profile; not enough time has passed since abandonment to see a clear result in PP.…”

“…Although our results show that abandonment did not increase the C and N pools (Table 1), the ecosystem will not reach a steady state quickly. Previous studies have indicated that soil C accumulation after paddy abandonment increases at poorly drained low land sites [23,24] and decreases at well-drained mountainous sites [25,26]. Abandoned upper terraced paddies are exposed to the atmosphere, while the lower slope position usually maintains high groundwater levels [27].…”