Nitrogen Study at Montana State

Montana State University reports that proper management of nitrogen fertilizer applications under flood and sprinkler irrigation optimizes sugarbeet yield and reduces nitrogen losses. Soil fertility specialist Clain Jones says a four-year study showed that sugarbeets grown in silty clay soil under sprinkler irrigation need less nitrogen than sugarbeets grown under flood irrigation. Jones, of the Department of Land Resources and Environmental Sciences, says the research at MSU's Eastern Agricultural Research Center at Sidney used available nitrogen rates, including fertilizer and residual soil nitrogen, at 100 to 200 pounds of nitrogen an acre. Nitrogen was applied (as 28-0-0) to sugarbeets under flood and sprinkler irrigation on silty clay soil. As the amount of applied nitrogen increased above optimum levels for yield, the amount of root and extractable sucrose yield decreased. "High nitrogen rates result in high root yields, yet reduces extractable sucrose. Low nitrogen rates result in reduced root yields, yet improves sugarbeet sucrose content," said Joyce Eckhoff, who conducted the research studies with Charles Flynn. Jones says nitrogen management is one of the most important aspects of sugarbeet production and provides a way to improve sucrose yield and quality. Root and extractable sucrose yield maximized at 175 pounds nitrogen an acre under flood irrigation. However, under sprinkler irrigation, root and extractable sucrose yield maximized at 125 pounds nitrogen an acre. "These results indicate that sugarbeets grown in silty clay soil under sprinkler irrigation need less nitrogen than sugarbeets grown under flood irrigation," Jones says. Flood irrigation delivered about three inches of water a cycle, while sprinkler irrigation delivered about one inch of water a cycle. About two times as many sprinkler cycles were used compared to flood cycles. During the growing season of all four years tested, groundwater nitrate concentrations were greater under flood irrigation than under sprinkler irrigation. In addition, unlike with flood irrigation, there was no drainage water under sprinkler irrigation. "This demonstrates that less nitrogen was lost through leaching and runoff for sugarbeets grown under sprinkler irrigation than under flood irrigation," Eckhoff says. "Since nitrogen lost to groundwater or runoff increases producers' nitrogen input costs, it is important to fine-tune nitrogen management to minimize those losses while maintaining sugarbeet root and sucrose yield," Jones says.