SOIL NITROGEN 



COMPARISON OF NITROGEN FERTILIZERS 



There are some outstanding differences between the nitrogen plots, especially 

 on the nonlegume subplots. The three plots without nitrogen have been 

 averaged to overcome their individuality. The plots with nitrogen have been 

 averaged for comparison with the other group but are also tabulated in- 

 dividually. Tables 4 and 5 are arranged to show the legume subplots and non- 

 legume subplots in separate groups with fertilizer nitrogen and with residual 

 nitrogen. 



Nitrogen was applied in 7 years out of the 12 recorded, but alfalfa and bar- 

 ley in 1933 were left uncut and subsequently plowed under. There are, there- 

 fore, 6 harvests from nitrogen in one group and 5 harvests from residual ni- 

 trogen in the other. On the legume subplots, the applications of nitrogen were 

 made on legumes with one exception, Japanese millet. Plot 10 with organic 

 nitrogen in dry fish was slightly superior to the others in the total yield of 

 dry matter, but Plot 5 with nitrate of soda was notably superior with the millet. 



Of the nonlegume subplots with fertilizer nitrogen, Plot 5 was superior to 

 the others in 1924, 1930, and 1935 and in total yield. Plot 10 was practically 

 equal to Plot 8, which received sulfate of ammonia. 



In the years with residual nitrogen, Plot 10 with its organic nitrogen residues 

 was always superior to Plot 5, which appeared to retain no nitrate residue 

 because it was inferior to the average production of the plots without nitrogen 

 except with grass in 1929. 



On the legume subplots, applications of nitrogen had little effect except on 

 the nonlegume, Japanese millet. Clovers were practically unaffected, soy- 

 beans were increased 7 percent, oats and peas 8.6 percent. The crops with 

 residual nitrogen were in the aggregate actually inferior to those without any 

 nitrogen. The net result for the application of 315 pounds per acre of nitrogen 

 in various forms was a total gain of 1460 pounds of dry matter and 7.5 pounds 

 of nitrogen, due mainly to the millet. 



Applications of nitrogen to the crops on the nonlegume subplots produced 

 an increase of 9860 pounds of dry matter, and 119.7 pounds of nitrogen. The 

 residual nitrogen on Plots 8 and 10 caused an average increase for the group 

 of 1190 pounds of dry matter and 16.7 pounds of nitrogen. The total gain 

 for the 315 pounds per acre of applied nitrogen was 11,050 pounds of dry 

 matter and 136.4 pounds of nitrogen. Only 43.3 percent of the applied nitro- 

 gen appeared to be recovered in the crops, 38 percent when applied and 5.3 

 percent with residual nitrogen. 



PREVIOUS TREATMENT WITH LIME 



All plots were dressed with hydrated lime in 1898 and 1905 at the rate of 

 2000 pounds per acre each time. The east half of each plot received hydrated 

 lime at the rate of 5000 pounds per acre in 1909 and 4000 pounds per acre in 

 1913. Liming was not repeated until 1919, when Plots 5, 7, 9, and 10 received 

 2000 pounds per acre of ground limestone on the north half of each plot. Plot 

 8 received an equal dressing over the whole plot, while Plot 6 was not given 

 any lime. 



