Abstract
Rice water-saving irrigation technology can remarkably reduce irrigation water input and maintain high yield; however, this technology can also accelerate the decomposition of soil organic matter in paddy fields. The spatial and temporal distributions of soil organic carbon (SOC), water-soluble organic carbon (WSOC), and soil microbial biomass carbon (SMBC) under different water-carbon regulation scenarios were analyzed on the basis of field experiments in the Taihu Lake region in China to explore the effects of biochar application on SOC and its components in water-saving irrigation paddy fields. The response of soil catalase (CAT) and invertase (INV) to biochar application in water-saving irrigated rice fields was clarified. The results showed that water-saving irrigation reduced the SOC content by 5.7% to 13.3% but increased WSOC and SMBC contents by 13.8% to 26.1% and 0.9% to 11.1%, respectively, as compared with flooding irrigation. Nonflooding management promoted the oxidative decomposition of soil organic matter. Two years after straw biochar was added, paddy soil SOC content under water-saving irrigation was increased by 4.0% to 26.7%. The WSOC and SMBC contents were also increased by 4.0% to 52.4% and 7.0% to 40.8%, respectively. The high straw biochar addition rate exhibited great impact on SOC. Remarkable correlations among SOC, WSOC, and SMBC were observed, indicating that the addition of straw biochar improved soil labile C, such as WSOC and SMBC, which promoted SOC transformation and stability in paddy soil under water-saving irrigation. Soil CAT and INV were related to SOC conversion. In conclusion, the combination of water-saving irrigation and straw biochar addition was beneficial to the improvement of soil properties and fertility of paddy fields.
Highlights
Carbon cycle is closely related to global energy balance and ecosystem productivity [1], and the soil carbon pool is the largest in terrestrial ecosystems [2]
The total soil organic carbon (SOC) content of controlled irrigation (CI) during the entire growth period was lower than that of conventional irrigation, and significant differences between 10 cm and 40 cm soil layer were observed at the tillering stage, 20 cm and 40 cm at the jointing and booting stage, and 0 cm and 40 cm at the milk stage (p < 0.05)
The SOC content in the controlled irrigated paddy fields decreased by 5.7% to 13.3%
Summary
Carbon cycle is closely related to global energy balance and ecosystem productivity [1], and the soil carbon pool is the largest in terrestrial ecosystems [2]. 1500 to 2000 Pg (1 Pg = 1015 g) of carbon is stored in soils in the form of organic carbon [3,4], accounting for more than half of the soil carbon pool worldwide; soil organic carbon (SOC) that exhibits active exchange with atmospheric components accounts for approximately two-thirds of the terrestrial ecosystem carbon [5]. The organic carbon in the soil is a carbon sink and source, and its small changes greatly alleviate or accelerate the concentration of atmospheric CO2 , thereby changing the global carbon cycle [6]. Public Health 2020, 17, 333; doi:10.3390/ijerph17010333 www.mdpi.com/journal/ijerph
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