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Soil Nitrate Concentrations under Corn as Affected by Tillage, Manure, and Fertilizer Applications

Agronomy Dep., Univ. of Maryland, College Park, MD 20742.

^* Corresponding author.

ABSTRACT

A 3-yr study was conducted to examine combination effects of tillage (no-till, conventional-till), manure, and inorganic fertilizer (ammonium nitrate) on leaching of nitrates from the root zone of corn (Zea mays L.). Soil cores were collected every spring to a depth of 210 cm and analyzed for NO₃-N. Leaching of NO₃-N significantly increased as fertilizer N rates increased, especially when rates exceeded the crop's potential to assimilate N. The concentration of soil nitrate (averaged over depth and tillage) in Year 3 of the study under the unfertilized control plots was 2.5 mg NO₃-N kg^–1, whereas the concentration under plots fertilized with 260 kg N ha^–1 was 8.7 mg NO₃-N kg^–1. Soil nitrate concentrations were consistently lower under no-tillage when compared with conventional-tillage. Tillage differences were greatest when high rates of N were added to soil. These results indicate that the use of no-tillage cultivation may reduce the leaching of nitrates beyond the crop root zone.

Scientific Article no. A6373 and Contribution no. 8557 of the Maryland Agric. Exp. Stn., Univ. of Maryland, College Park, MD 20742.

This work was supported, in part, by a grant from the Maryland Dep. of Agric.

Received for publication July 9, 1991.