Nitrate Leaching Potential from a Single Border-Flood Irrigation

Groundwater contamination by nitrate and other chemicals is a public concern and has subjected agriculture to scrutiny. Field studies were conducted at the Maricopa and Marana Agricultural Centers in 1989 to 1990 to document nitrate leaching potential with border flood irrigation. Calcium nitrate fertilizer was applied at various rates along with potassium bromide, which serves as an additional indicator of nitrate movement. Approximately 8.55 inches of irrigation water was applied at the Maricopa site on a sandy loam soil and 4.0 inches of irrigation water was applied at the Marana site on a clay loam soil. At the Maricopa site, only 64% of the nitrate could be accounted for in the top 6.7 ft. while most of the nitrate was found in the top 4 to 5 ft. at Marana. The water and nitrate moved 3 to 4 times deeper than predicted in the absence of preferential flow