Abstract
Straw incorporation is strongly recommended in rice paddy to improve soil quality and mitigate atmospheric carbon dioxide (CO2), via increasing soil organic carbon (SOC) stock. However, straw application significantly increased methane (CH4) emission during rice cultivation, and then its incorporation area was not expanded effectively. To find the reasonable straw management practice which can reduce CH4 emission without productivity damage, the effect of straw incorporation season and method on CH4 emission was investigated at six different textured paddy fields in South Korea for 2 years. A straw was applied right after rice harvesting in autumn, and the other right before rice transplanting in spring. In the autumn application, straw was applied with two different methods: spreading over soil surface or mixing with soil. Straw application significantly increased seasonal CH4 flux by average 28–122% over 197–590 kg CH4 ha−1 of the no-straw, but its flux showed big difference among straw applications. Fresh straw application before transplanting increased seasonal CH4 flux by approximately 120% over the no-straw, but the autumn application reduced its CH4 flux by 24–43% over 509–1407 kg CH4 ha−1 of the spring application. In particular, the seasonal CH4 flux was approximately 24% lower in straw mixing with soil after autumn harvesting than 423–855 kg CH4 ha−1 in straw spreading over surface. However, CH4 fluxes were not significantly discriminated by soil and meteorological properties in the selected condition. Straw application slightly increased rice grain yield by approximately 4% over the no-straw, but rice productivity was not statistically different among straw applications. Spring straw application increased CH4 intensity which means seasonal CH4 flux per grain yield by the maximum 220% over the no-straw. Autumn straw application significantly decreased CH4 intensity by average 24–65% over the spring straw application. In particular, CH4 intensity in straw mixing with soil treatment was not statistically different with the no-straw. Therefore, autumn straw application with mixing inner soil could be a reasonable straw management practice to decrease CH4 emission impact with improving soil productivity.
Highlights
Soil organic carbon (SOC) stock is accepted as the most key parameter to decide soil health condition and sustainability [1]
Experimental site selection To evaluate the effect of straw managements on seasonal CH4 flux in Korean rice fields, six typical rice paddies having different soil texture were selected in three different locations (Central, Honam, and Youngnam area) of south Korean Peninsula (Table 1)
Methane emission during rice cultivation Irrespective with soil amendments, similar CH4 emission patterns were observed in each field during rice cropping seasons (Fig. 1)
Summary
Soil organic carbon (SOC) stock is accepted as the most key parameter to decide soil health condition and sustainability [1]. Soil C sequestration, which means transferring a greenhouse gas carbon dioxide (CO2) into long-lived pools and storing. Increasing SOC stock is recognized as the most promised soil management strategy to achieve sustainable soil quality and mitigate global warming [3, 4]. Several soil management practices such as tillage, fertilizer, water, organic matter, winter cover crop, and crop rotation managements were recommended to increase SOC stock in arable lands [5]. Straw recycling is accepted as the most reasonable agricultural practice to increase SOC stock in mono-rice paddy [6].
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