Long-term trends in nitrate leaching across the KBS LTERtreatments

Parr, S. and G.P. Robertson

Presented at the All Scientist Poster Reception (2006-05-09 )

Abstract: Hydrologic nitrogen losses from managed ecosystems affect plant nitrogen availability and cause ground and coastal water eutrophication and drinking water contamination: greater than 10% of the domestic drinking-water wells in the Midwest contain unsafe levels of nitrates. We tested the impact of management intensity on the level of nitrogen loss through nitrate leaching. Quartz soil water samplers were used to sample leachate from four annual cropping systems (corn-soybean-wheat rotations managed as conventional, no-till, low-input, and organic systems), two perennial cropping systems (alfalfa and poplar trees), two successional systems (early and mid-successional old fields), and two forest systems (planted conifer and native deciduous systems) all replicated on the same soil series. Samples were collected twice a month from March 1995-November 2005, and analyzed for inorganic nitrogen. Nitrate leaching was highest in annual agricultural plots and perennial alfalfa plots. Successional plots and plots with trees (fast growing poplar clones) showed the lowest leaching levels, while native forested sites showed intermediate levels of nitrate levels. Within agricultural systems, conventional tilled and no-tilled systems showed higher leaching losses than organic systems. These results suggest the potential to reduce nitrate leaching in agricultural systems through greater investments in nitrogen management and reducing nitrogen applications to crops. Results also suggest the potential for large nitrogen losses from forage crops where no inorganic nitrogen is being applied. Additionally, these results may be useful in predicting the impact of land use change on water quality.

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