Temporal variations in carbon stocks and soil fertility in Inceptisols after 12 years of paddy rice cultivation

Background and aimsMonitoring temporal trends in soil properties under rice paddy ecosystems is key for efficient soil management interventions toward sustainable and climate-smart rice production. The objectives of this study were to thoroughly investigate the temporal variations of measured soil properties and evaluate the changes in carbon stocks and soil fertility over a 12-year period under intensively managed rice paddy fields.MethodsA total of 2110 sampling points in paddy rice fields under the same agronomic management were identified. Composite soil samples from the topsoil (0 - 15 cm depth) were collected from each sampling point in each sampling year (2007, 2011, 2015, and 2019) and comprehensively analysed.ResultsAfter 12 years of intensive rice cultivation, soil organic matter significantly increased from 25 g kg-1 to 29.3 g kg-1, with an annual rate of change of 0.33 - 0.34 g kg-1. Within the 12-year period, available phosphorus significantly increased from 130.87 to 140.80 mg kg-1, with a rate of change of 0.83 - 0.95 mg kg-1 year-1. The C stocks increased in the subsequent years with a relative change ratio of 0.94 and 3.91% in 2015 and 2019, respectively.ConclusionIn a span of 12 years, intensive rice cultivation resulted in an increase in soil fertility. Among the identified soil factors, soil pH, organic carbon, exchangeable calcium, and available silicate were positively associated with soil fertility improvement. This study is crucial for the development of sustainable soil management interventions and climate-smart agricultural systems in intensively cultivated rice paddy ecosystems.