Controlled Irrigation and Drainage Reduce Rainfall Runoff and Nitrogen Loss in Paddy Fields

Area of Science:

• Agricultural Science
• Environmental Science
• Hydrology

Background:

• Nutrient loss from paddy fields is a major source of agricultural nonpoint source pollution in southern China.
• Unreasonable irrigation and drainage practices exacerbate nutrient runoff during the rice growing season.
• The dynamics of runoff and nitrogen loss under various irrigation strategies remain unclear.

Purpose of the Study:

• To investigate the effects of controlled irrigation and drainage on runoff and nitrogen loss in paddy fields.
• To compare nutrient loss between traditional and controlled irrigation and drainage modes.
• To provide insights for reducing agricultural nonpoint source pollution.

Main Methods:

• Field experiments were conducted to monitor runoff and nitrogen loss.
• Observations were made during typical rainfall events and throughout the entire rice growth period.
• Measurements included drainage volume, peak drainage, and concentrations of total nitrogen, nitrate nitrogen, and ammonium nitrogen.

Main Results:

• Controlled irrigation and drainage reduced drainage volume by 47.5% and 31.3% in two rainfall events.
• Peak drainage was decreased by 38.9% and 14.4% under the controlled mode.
• Average nitrogen concentrations (total, nitrate, ammonium) were reduced by 11.4% to 27.8% during rainfall events.
• Total nitrogen, nitrate nitrogen, and ammonium nitrogen loads were reduced by 65.3% to 69.8% compared to the traditional mode.

Conclusions:

• Controlled irrigation and drainage effectively reduces drainage and nitrogen loss in rice paddy systems.
• Increased retention time in paddy fields and drainage ditches enhances nitrogen removal.
• This approach offers a viable strategy for mitigating agricultural nonpoint source pollution.