Masters Theses

Date of Award

12-1975

Degree Type

Thesis

Degree Name

Master of Science

Major

Plant, Soil and Environmental Sciences

Major Professor

G. M. Lessman

Committee Members

V. H. Reich, C. H. Shelton

Abstract

Experiments were conducted in 1974 on the Middle Tennessee Experiment Station at Spring Hill and on the Milan Field Station at Milan to determine the effect of different cultural factors on some quality parameters of runoff from small agricultural watersheds. There were a total of 5 watersheds utilized in this study, 2 at Middle Tennessee and 3 at Milan. Water samples were collected by automated water sampling equipment at 30 minute intervals, and were analyzed for dissolved solids, nitrate-nitrogen, chlorides, and orthophosphate-phosphorus. The experimental design was a nested design. Simple regression and correlation were performed using runoff rate as the independent variable. As there were not equal numbers of observations from each watershed, a special modification of Duncan's New Multiple Range, developed by Kramer, was used to separate means. There were a total of 615 samples analyzed. There was no signifi-cant difference in mean dissolved solids among watersheds with Milan Field Station (MFS) watershed 1, a 40 acre tract in cotton, being slightly lower than the other 4 watersheds. Nitrate-N values were higher on all of the Milan watersheds although not significantly so. Middle Tennessee Experiment Station (MTES) watershed 1, 198 acres in com, soybeans, and pasture, MTES 2, a 12 acre pasture, and MFS 2, 67 acres in cotton, soybeans, and woodland, were significantly higher in mean C1 concentration than MFS 1 or MFS 3, a 9 acre field in soybeans. which were significantly the same. The P concentrations were much higher at the MIES watersheds (over 4 times higher) with MTES 2 signifi-cantly higher in P than any other watershed. This was to be expected since most of the soils at Middle Tennessee are very high in P with several of the soils classified as phosphatic. Only at MFS 1 did the maximum NO3-N concentration exceed the level of 10 parts per million (ppm) established as the maximum level permissible for public drinking water and this occurred in only 3 samples. The highest mean concentration was 2.2 ppm on MFS 2 which is well within acceptable limits. The mean runoff rate during rainfall events producing runoff ranged from 0.85 cubic feet per second (cfs) on MFS 2 to 5.08 cfs on MFS 1. The highest nutrient and dissolved solids losses came from MFS 1 which had the 5.08 mean cfs runoff. Watershed MFS 1 had 20 times more dis-solved solids, 25 times more NO3-N, 8 times more Cl, and triple the P losses of the next highest watershed for these nutrients and dissolved solids. Month and rainfall event definitely affected the nutrient concentration of the runoff. Rainfall was significant at nearly every watershed. The exact significance of the rainfall event was impossible to determine since it often rained at one location and not the other, and watersheds at the same location received differing rainfalls. Equipment malfunction also prevented the same number of samples from being taken on each watershed during runoff events. The statistical analysis used determined that significant differences existed among rainfalls. Significant differences among months were found for dissolved solids at MTES 2, MFS 1, and MFS 2. Differences among months were also significant at MFS 2 and MFS 3 for NO3-N, only at MFS 2 for Cl, and for P at MTES 2, MFS 1, and MFS 2. Regression values were negative, suggesting that an inverse relationship existed between nutrients and dissolved solids and runoff rate.

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