SULFATE OF AMMONIA. 97 



showed that it was not enough two successive seasons. Therefore it is 

 best to apply the Ume generously in form of finely ground limestone or 

 the fine hj^drated lime, as has been done in Field A. 



C0MPAILA.TIVE Effects of Nitrate of Soda, Sulfate of Ammonia and 



NO Nitrogen. 



As stated in the beginning of this bulletin, it was not planned to include 

 the results obtained with other nitrogenous fertilizers, but it has seemed 

 best at this point to present the summar}^ of the comparative effects pro- 

 duced by nitrate of soda and sulfate of ammonia which was last pub- 

 lished in 1916, ^ the figures in which were as follows: nitrate of soda, 100; 

 sulfate of ammonia, 88. 8; no nitrogen, 73.4. This summary includes all 

 the yields on the respective groups of plots. 



It has been shown in the preceding pages that liming the soil produces 

 marked benefit with sulfate of ammonia. Therefore a special summary 

 has been calculated in which the yields for the years 1898, 1899, 1900, 

 1905 and 1906, when the effects of liming were due to applications over the 

 entire plots, have been combined with those of the limed portions obtained 

 in 1914, 1915, 1917 and 1918. This combination produced the following 

 comparison: nitrate of soda, 100; sulfate of ammonia, 91.6; no nitrogen, 

 70. 



The comparative effects in 1919 and 1920 were: nitrate of soda, 100; 

 sulfate of ammonia, 100; no nitrogen, 70. The improvement in the pro- 

 duction by sulfate of ammonia is possibly due to the nature of the crops. 

 Under favorable conditions and in the presence of lime, both corn and 

 timothy respond to sulfate of ammonia; and with its long growing season, 

 corn is especially adapted to use the substance. 



Conclusions. 



Sulfate of ammonia has been effective as a fertilizer when accompanied 

 by an application of lime. In the absence of lime it has sometimes been 

 injurious, due to the formation of soluble compounds of manganese, 

 aluminium and iron. Injury has been greatest in dry periods when the 

 lessened soil moisture becomes more concentrated with soluble salts. 



Sulfate of ammonia has been particularly effective on the cereals — 

 corn, oats, rye and millet — when these crops have not followed a clover 

 crop. Potatoes have not been benefited bj' the sulfate of ammonia in 

 these trials. Soy beans, when uninoculated, responded well to the am- 

 monia; but its effects grew less as the root nodules increased in the later 

 years. Clover has not been much benefited by the sulfate of ammonia, 

 but mi.xed grasses in 1920 were much increased by it. 



In general, the sulfate of ammonia has been about nine-tenths as 

 effective as nitrate of soda, per unit of nitrogen. 



1 Mass. Agr. Expt. Sta., 28th Ann. Ropt. 



