74 MASS. EXPERIMENT STATION BULLETIN 165. 



continued use of ammonium sulfate brought the soils into an acid condition 

 which could be corrected by liming. Hall and Miller^ found that when 

 ammonium salts were used as a fertilizer the loss of calcium carbonate was 

 equivalent to the acid of the ammonium salt used. Nitrate of soda and 

 manure diminished this loss of calcium. Hall and Gimingham^ state 

 that the continuous application of ammonium salts brought soils into an 

 acid condition, and that the reaction was a double decomposition between 

 calcimn humate and the ammonium salts. In a later publication HalP 

 states that the acidity was caused by micro-fungi in the soil, which spUt 

 up the ammonium siilfate to obtain the ammonia, thereby setting free sul- 

 furic acid. Hunt " found that an acid condition, proving especially harm- 

 ful to corn and clover, resulted from the continued application of ammo- 

 nium sulfate. 



The conditions produced by the continuous application of ammonium 

 sulfate on crops, as reported by these investigators, are very similar to the 

 conditions on the nitrogen field at this experiment station. 



Soil used in the Experiments. 



The soil used for the various experiments herein described was taken 

 from one of the oldest fields on the station farm. A record of this field has 

 been kept for thirty-three consecutive years, and in that time it has re- 

 ceived only chemical fertilizers. Since 1890, when the present scheme of 

 fertihzing was inaugurated, the field has been used to compare different 

 forms of nitrogen fertilizers. The plots are one-tenth acre in area and 

 have a 2-inch tile drain running through the center of each plot at an aver- 

 age depth of 3 feet. 



The chemicals applied since 1890 to the plots studied have been as 

 follows : — 



Table I. — Chemicals applied annually. 

 Plot 0. Manure, dissolved bone black, sulfates of potash and magnesia. 

 Plot 1. Nitrate of soda, dissolved bone black, muriate of potash. 

 Plot 5. Sulfate of ammonia, dissolved bone black, sulfates of potash and mag- 

 nesia. 

 Plot 6. Sulfate of ammonia, dissolved bone black, muriate of potash. 

 Plot 7. No nitrogen, dissolved bone black, muriate of potash. 

 Plot 8. Sulfate of ammonia, dissolved bone black, muriate of potash. 



The amoimts applied have been 45 pounds of nitrogen per acre in nitrate 

 of soda, suKate of ammonia or manure, 80 pounds of phosphoric acid per 

 acre in dissolved bone black, and 125 pounds of potash per acre in muriate 

 of potash or double sulfates of potash and magnesia. On plot the phos- 

 phoric acid and potash naturally present in the manure have been supple- 

 mented by enough chemicals to make 80 pounds of phosphoric acid and 



1 Hall and Miller, Proc. Roy. Soc, Ser. B 77, No. B 514. 



2 Hall and Gimingham, Jour. Chem. Soc, Vol. 91 (1907), No. 534. 



3 Hall, Jour. Roy. Agr. Soc, 70 (1909), p. 12. 

 * Hunt, Bui. 90, Penn. State Exp. Sta. 



