EFFECT OF FERTILIZERS ON MOWINGS 7 



An Experiment in Which Only Nitrogen Fertilizers Were Used 



In view of the marked response to nitrogen obtained in the preceding experi- 

 ment, it was decided in 1932 to start a second experiment for the purpose of 

 studying the effect of nitrogen fertilizer alone on an old mowing. The history 

 of the field chosen for the experiment and the soil conditions were similar to those 

 of the previous experiment, except that the soil was more gravelly and more 

 subject to drouth. The size of the harvested portion of the plots was 40 by 13.6 

 feet, or one eightieth of an acre, and each treatment was replicated 5 times. 

 The fertilizers were used in such quantities as would furnish 50 pounds of nitrogen 

 per acre. In Table 5 are listed the fertilizers and the mean yield of hay for three 

 years. Only one cutting of grass was made each year. In the first two years the 

 weather was so dry during the latter part of the summer that the rowen crop 

 was a failure. In the third year it was decided, on account of weediness, to plow 

 after the first cutting, and reseed. 



Table 5. — Mean actual and relative yields of dry matter in hay for 



three years. 



1932 1933 1934 Mean 



Treatment 



No nitrogen 



Sodium Nitrate 



(Champion) 



Ammonium Sulfate 



(Arcadian) 



Calcium Cyanamide 



(granular) 



Urea 



Owing to lack of consistency of these results and to the comparatively short 

 duration of the experiment, it can be considered only as showing a trend in 

 respect to the relative value of the forms of nitrogen used. However, it is quite 

 positive in showing that nitrogen in any form used was very effective in increasing 

 yields. Yields were practically doubled in all cases by the use of a nitrogen fertil- 

 izer. 



In 1934 samples of grass were taken at intervals of about two weeks from the 

 plots which received different nitrogen fertilizers and analyzed for total nitrogen. 

 At the first sampling the grass was 8 to 10 inches high; at the second, 16 to 20 

 inches high; and at the third, which was also the time of mowing for hay, 30 to 

 36 inches high. The results, expressed as percentage of protein, are given in Table 

 6. These figures show that in the earliest stage of growth the effect of the nitrogen 

 fertilizers in increasing the protein content of the grass was relatively strong, the 

 increase being from about one fourth to one half of the check; that it was con- 

 siderably less by the time of the second sampling; and that it had practically 

 disappeared at the time of mowing. As between the first and last samplings, 

 there was an increase in the percentage of dry matter, while the protein content 

 decreased correspondingly in the case of the fertilized grass. As the crop ap- 

 proaches maturity the excess nitrogen is apparently used in metabolic processes, 

 and the final effect is reflected in the increased yield of the mature crop. The 

 data are considered inadequate for the drawing of any conclusion as to the rela- 

 tive merits of the several nitrogen carriers in increasing the percentage of protein. 



