A Study of the Relations Between Plant Growth 

 AND Combined Nitrogen in Winona Lake.! 



Thuhmax B. Rice. 



Objective. The purpose of the investigation as it was first conceived was 

 to determine the effect of combined nitrogen content of the water upon the 

 luxuriance of plant growth. As the work progressed, however, a considerable 

 mass of data accumulated pertaining to the effect of the vegetation upon the 

 nitrogen content of the water, and so the scope of the work was broadened 

 to include this phase of the subject. 



Preliminary Work. Work was begun in Juh', 1915, by making an accurate 

 map of the lake, and bj' making a close study of the entire littoral region 

 in order to determine the most fruitful points of attack. The entire shoreline 

 was sounded at close intervals to a depth of five meters, this being found to 

 be the limit of plant growth. The Lake was under constant observation 

 from Juh', 1915, to September, 1916. During this time observations of some 

 kind were taken nearly every day except while the lake was covered with ice. 



Analyses. Analyses were begun in October and continued until August. 

 In all, 135 analyses were made. About half of the analyses were complete 

 for combined nitrogen, the others being for nitrates and nitrites only. Stand- 

 ard methods of water analysis were used (]Mason, '12 and Olsen, '08.)* 



Samples were taken from clear unfiltered water just below the surface 

 unless otherwise stated. The bottle used to carry samples were thoroughly 

 cleaned and was sealed immediatelj^ after being filled. Analj^sis was begun 

 as soon as the laboratory was reached, on the average about thirty minutes 

 after the sample was taken. 



A map of the lake with analysis stations is presented as Fig. 1. 



Description of the Stations from which analyses were made. 



A Weedy, numerous confervoid algae, muddy sediment bottom. 

 B Weeds scanty, but dense close by, sediment bottom. 4m deep. 

 C Clear water, near center of the lake, deepest place, 21m deep. 

 D Weedy, many algae, muddy sediment bottom. 

 E and G Very weedj^ water much contaminated, Im deep. 



tContribution of the Zoology Department of Indiana University No. 156. The 

 problem was suggested by Dr. Will Scott under whose direction the work was 

 carried out. 



*Mason, E.xainination of Water, 1912: Wiley and Sons. 



Olsen, Quant. Chem. Anal. 1908, Van Xo.strand. An error of one decimal place in 

 the computation of nitrites as' given in the 1908 edition (corrected in 1915 edition; was 

 detected and computations were made accordingly. 



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