Boles, J.C.
Presented at the All Scientist Meeting (1999-07-20 to 1999-07-21 )
The magnitude and importance of dissolved organic nitrogen (DON) as a vector for hydrologic N loss has been largely ignored in agricultural systems. It has only been measured in the surface horizons even in the few forested systems where DON has been studied. The KBS LTER provided the opportunity to measure and compare DON loss between agronomic and forested systems. Teflon suction lysimeters were installed in the C horizon under treatments 1-7 and in coniferous, deciduous, and old field successional sites. DON loss in agronomic systems was low compared to NO3- , but was 20 to 100% of total loss in perennial crops and successional systems due to generally low total N loss. Nitrate and total N loss tended to be greatest in the fall, but DON appeared to have no seasonality except in 3 treatments. DON concentrations were generally around 1 mg/l , whereas NO3 ranged up to ~ 60 mg/l. Nitrate loss was greatest under the four annual cropping systems. The low and zero input treatments had significantly higher nitrate loss than the perennial and successional treatments suggesting that increased N cycling, not inputs, are the cause.
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