Controlling nitrate leaching in irrigated agriculture

Area of Science:

• Agricultural Science
• Environmental Science
• Hydrology

Background:

• Groundwater quality is crucial for ecosystems and human use.
• Agricultural practices, particularly irrigation and nitrogen (N) fertilization, significantly impact groundwater nitrate (NO3-N) levels.
• Assessing the effectiveness of different management strategies is vital for sustainable agriculture.

Purpose of the Study:

• To evaluate the impact of improved irrigation and nutrient management practices on groundwater quality.
• To compare the effects of conventional furrow irrigation versus surge and center pivot irrigation with reduced N inputs.
• To analyze the influence of crop type (corn vs. alfalfa) on groundwater quality.

Main Methods:

• Groundwater quality was monitored from 1991 to 1996 at 31 multilevel samplers across four management fields.
• Data were collected at 16 depths, three times annually.
• Groundwater dating (3H/3He) was used to determine water age and aquifer stratification.

Main Results:

• Center pivot irrigation with reduced N fertilizer and water inputs significantly decreased N leaching compared to conventional furrow irrigation.
• A wet growing season in 1993 diluted NO3-N concentrations in shallow groundwater.
• Nitrate levels beneath center pivot-irrigated corn fields remained lower than conventional and surge-irrigated fields, indicating reduced leaching.

Conclusions:

• Sprinkler irrigation combined with N fertigation is an effective strategy to reduce nitrogen leaching into groundwater.
• These improved practices can significantly reduce N leaching with minimal impact on crop yield.
• Management strategies can be tailored to protect groundwater resources while supporting agricultural productivity.