Abstract
Nutrient losses from sloping farmland in karst areas lead to the decline in land productivity and nonpoint source pollution. A specially tailored steel channel with an adjustable slope and underground hole fissures was used to simulate the microenvironment of the "dual structure" of the surface and underground of sloping farmland in a karst area. The artificial rainfall simulation method was used to explore the surface and underground runoff characteristics and nutrient losses from sloping farmland under different rainfall intensities. The effect of rainfall intensity on the nutrient loss of farmland on karst sloping land was clarified. The results showed that the surface was the main route of runoff and nutrient loss during the rainy season on sloping farmland in karst areas. The influence of rainfall intensity on the nutrients in surface runoff was more substantial than that on underground runoff nutrients. Nutrient loss was more likely to occur underground than on the surface. The losses of total nitrogen, total phosphorus, and total potassium in surface and underground runoff initially increased and then gradually stabilized with the extension of rainfall duration and increased with increasing rainfall intensity and the amount of nutrient runoff. The output of nutrients through surface runoff accounted for a high proportion of the total, and underground runoff was responsible for a low proportion. Although the amount of nutrients output by underground runoff was small, it could directly cause groundwater pollution. The research results provide a theoretical reference for controlling land source pollution from sloping farming in karst areas.
Highlights
Soil nutrient loss is a universal phenomenon worldwide [1], and how to control and prevent nutrient loss is a focal point of international research [2, 3]
Runoff output process and distribution characteristics under different rainfall intensities Due to the unique "dual structure" of the karst area, surface runoff will form down the slope after rainwater falls on sloping farmland, and underground runoff will be lost through cracks
After 15 minutes of rain, the surface runoff modulus was maintained within the range of 0.09~0.77 L min-1 m2 at 90 mm h-1, and the underground runoff modulus under the same rainfall intensity was from 0.10~0.37 L min-1 m2 after this period
Summary
Soil nutrient loss is a universal phenomenon worldwide [1], and how to control and prevent nutrient loss is a focal point of international research [2, 3]. The demand for food has increased as the population has grown.
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