Disposition of 15N-Labeled Fertilizer Nitrate Applied During Corn Culture in Field Lysimeters
1978
Chichester, F. W. | Smith, S. J.
Calcium nitrate [Ca(NO₂)₂] labeled with 5.5% ¹⁵N was applied 336 kg/ha nitrogen (N) to each of two conventional tillage and two mulch minimum tillage field lysimeters continuously cropped to corn (Zea mays L.). Disposition of the labeled N was followed for 3 years, particularly relative to its effect on water quality. Soil profile samples were taken prior to and at the end of the experiment. Runoff was sampled by event, and percolate was sampled twice weekly. The corn crop was sampled at harvest each year. Samples were analyzed for inorganic and/or total N and percent ¹⁵N. An accounting of applied ¹⁵N for the study period showed that <2% moved in runoff, approximately 30% was leached in percolate, 25 to 30% was recovered by the corn crop, and from 10 to 30% remained in the soil. On the basis of a balance sheet constructed from the data, ¹⁵N gaseous loss (presumably mainly by denitrification) was estimated to range from 6 to 26% of that applied. The magnitude of gaseous loss of N appeared to vary as a function of lysimeter management history, with the systems under improved soil fertility management exhibiting less gaseous loss due to greater immobilization of ¹⁵N in the soil organic fraction.
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