Runoff nitrogen losses under confluence and diverging drainage systems in the sloped plot scale: A comparative study

Area of Science:

• Agricultural Engineering
• Environmental Science
• Soil Science

Background:

• Drainage systems are crucial for managing nutrient runoff from sloping farmlands.
• Confluence and diverging drainage layouts are common but their comparative impact on nutrient loss is unclear.

Purpose of the Study:

• To investigate the effects of confluence and diverging drainage systems on nitrogen (N) runoff losses in sloped plots.
• To compare nutrient loss characteristics (total nitrogen, dissolved nitrogen, particulate nitrogen) under different drainage configurations and slope gradients.

Main Methods:

• Laboratory rainfall simulations were conducted on bare slopes (CK), confluence drainage (T1), and diverging drainage (T2) systems.
• Runoff nutrient concentrations and losses were analyzed under 1.8 mm/min rainfall intensity and 5°, 10°, 15° slope gradients.
• Key parameters measured included total nitrogen (TN), dissolved nitrogen (DN), particulate nitrogen (PN), and the DN:TN ratio.

Main Results:

• Confluence drainage (T1) significantly reduced accumulated runoff depth, TN, and PN losses compared to both bare slopes (CK) and diverging drainage (T2).
• T1 showed the lowest dissolved nitrogen (DN) concentration at a 5° slope.
• Diverging drainage (T2) delayed runoff time but was less effective in reducing overall N losses compared to T1.

Conclusions:

• Drainage systems are effective in reducing nutrient runoff losses from sloped plots.
• Confluence drainage systems demonstrate superior performance in minimizing nitrogen runoff losses compared to diverging drainage systems.
• The findings highlight the importance of selecting appropriate drainage layouts for effective nutrient management in agriculture.