EXPERIMENTS WITH NITROGEN FERTILIZERS 9 



with the object of building up the plots that did not receive nitrogen in fertihzer, 

 because it had become definitely established that leguminous plants, of which 

 the soy bean was one type, were able to use nitrogen from the air for their growth 

 and their stubble and roots would thereby enrich the soil with the nitrogen 

 contained in them. Consequently, the oat crops of 1893, 1895, and 1897 fol- 

 lowed soy beans, the roots and stubble of which were left in the soil. 



The effect of the first soy bean crop appeared beneficial, especially in the pro- 

 duction of oat straw which was double the quantity produced in 1890. Nitrogen 

 is regarded as a promoter of vegetation rather than fruit. The Plots 4, 7, and 9 

 were especially improved in both straw and grain. 



The crop of 1895 showed no gains over 1893 in production of straw, except on 

 Plot 8. This plot had received a dressing of 200 pounds of air-slaked lime the 

 year before, which stimulated a larger yield of so}' beans and apparently increased 

 vegetation in the oats of this year. The yield of grain was larger than in 1893 

 on 8 of the plots, which included all the different kinds of fertilizer. 



In 1897, the production of straw decreased on all but the nitrate plots, 1 and 

 2, and the yields of grain were less on all but Plot 8. Plots 4, 7, and 9 had shrunk 

 in both grain and straw to a lower point than in 1890. The rotation with soy beans 

 had not resulted in any permanent improvement in soil fertility. 



Before sowing the oats in 1898, the entire field was limed with approximately 

 2000 pounds per acre of freshly slaked lime. The yields on all plots were much 

 lower than in 1897 and excepting Plot 8 even less than in 1890. This is similar 

 to the result of repeated crops of corn ending in 1889. 



Table 2 — Yield of Oats 



(Pounds per plot.) 



*Lime applied. 



The comparative efficiency of the four different kinds of nitrogen fertilizers 

 is not readily determined in these successive oat crops. There is but one manure 

 plot against two plots with nitrate, two with blood and three with ammonia. 

 Manure must necessarily stand by its one annual crop. The two nitrate crops 

 may be averaged and also the two blood crops. It is problematical how to com- 

 pare the ammonia crops fairly with the others. It has been thoroughly demon- 

 strated that ammonium sulfate should have the benefit of the presence of calcium 



