Effects of cornstalk mulching and rainfall intensity on the quantity and quality of dissolved organic carbon in runoff: A field rainfall simulation at the plot scale

Abstract

AbstractUnderscoring how crop mulching changes the dissolved organic carbon (DOC) in runoff is essential to understanding the sustainable application of cornstalk mulching. This study examined the runoff DOC quantity and quality in plots with and without cornstalk mulching under various rainfall intensities in a representative steep fallow land of southwestern China. Field rainfall simulations within a 60 min duration were conducted on the triplet plots (1.5 m × 1 m for a single plot) with bare soils under 30‐ and 90‐mm h−1 intensities and with cornstalk mulching (air‐dried whole plants with 60% coverage and weight 1.65 kg per plot) under 90 mm h−1 intensity, respectively. The concentration and loss of runoff DOC and its quality variables, including SUVA254 (aromaticity of DOC), C:C (proportion of colored humic substances in DOC), and E4:E6 (fulvic acid to humic acid in DOC), are determined. Results showed that runoff DOC concentration and loss were both significantly higher at 90 mm h−1 intensity than at 30 mm h−1 intensity (p < 0.05), simultaneously, they were 52.6% and 53.2% higher in mulched plots than in bare plots (p < 0.05), respectively. Runoff SUVA254 and C:C in bare plots were 90% and 88.9% higher in 30 mm h−1 intensity than in 90 mm h−1 intensity (p < 0.05), respectively. Whereas, E4:E6 of runoff was 12.3% higher in mulched plots than that in bare plots (p < 0.05). Our findings imply that cornstalk mulching enhances the export of runoff DOC with a decline in aromaticity and the molecular weight of humic substances.