![Masters Theses](../../assets/md5images/ebc0648ded2cd429f55e0a2fe4407546.gif)
Masters Theses
Date of Award
12-1990
Degree Type
Thesis
Degree Name
Master of Science
Major
Plant, Soil and Environmental Sciences
Major Professor
John G. Graveel
Committee Members
Don Tyler, Paul Denton, Bob Duck
Abstract
Nitrate-nitrogen distribution to a depth of 274 cm was evaluated in long term no-tillage corn plots subjected to three nitrogen rates and three cover situations. The soil on the experimental area was mapped Memphis silt loam (fine-silty, mixed, thermic, Typic Halpudalfs). The design of the experiment was randomized block with split-plot arrangement of treatments. The treatments were five levels of nitrogen and five cover situations. Main plots consisted of nitrogen rates and cover crops formed sub-plots. Soil samples were collected at 15 cm depth intervals down to 90 cm and at 30 cm intervals from 91 to 274 cm. Soil solution was obtained using vacuum displacement and nitrates determined by ion chromatography.
Corn (Zea mays L.) yield increased with an increase in nitrogen rate. Beyond 168 kg N ha-1 there were no significant differences in corn yield. Below 112 kg N ha-1 yields of corn following hairy vetch (Vicia villosa Roth.) were significantly greater than those following wheat (Triticum aestivum L.) and corn stubble. Nitrate-nitrogen accumulation was highest where 224 kg N ha-1 was applied and where hairy vetch was seeded as a cover crop. The highest NO3 concentration in soil solution occurred in August. Mean NO3-N concentration from vetch, wheat and no cover were 32, 25, and 28 μg mL-1 respectively. The top 30 cm of soil contained 37% of the total NO3-N. At 0 kg N ha-1 there were no significant differences in NO3-N accumulation at each depth interval from 0 to 274 cm. At 168 kg N ha-1, significant NO3-N accumulation occurred at depths below 122 cm. Raising the nitrogen rate to 224 kg ha-1 resulted in no significant differences among depths for NO2-N accumulation for all cover situations. Plots seeded to wheat had the least NO2-N accumulation at all depths. Electrical conductance followed the trend of NO2-N distribution. Soil pH varied greatly in April and was constant in August and November. Significant differences existed among depth intervals for both pH and electrical conductance. No significant differences were observed among cover crops.
Recommended Citation
Kawonga, Wickson Temwa, "Evaluation of nitrate distribution in long-term no tillage corn production under three cover situations and three rates of nitrogen. " Master's Thesis, University of Tennessee, 1990.
https://trace.tennessee.edu/utk_gradthes/7125