SOIL NITROGEN 



11 



Plots 5, 6, and 8 had received sulfate of ammonia as the nitrogen fertilizer 

 each year until the beginning of the present experiment. The results of this 

 unequal liming were noticeable. The crops of corn in 1919 and of hay in 1920 

 and 1921 have been reported in Bulletin 290. Plot 8 was superior to the other 

 two and Plot 6 inferior to the others. The corn crop of 1922, unreported until 

 now, showed the west half of Plot 6 to be nearly barren, due to toxic com- 

 pounds formed in the soil from the sulfate of ammonia in the absence of car- 

 bonate of lime. The reserve of lime on the east half maintained the yield at 

 the level of Plot 8. The southwest quarter of Plot 5 was nearly as bad as the 

 west half of Plot 6, and its northwest quarter was inferior to Plot 8. Table 7 

 shows the yields by quarter-plots. 



PREPARATORY TREATMENT WITH LIME 



In 1923 graduated amounts of ground limestone were applied to the plots 

 in the spring before corn was planted. Plots 5, 9, and 10 received 1000 pounds 

 per acre on the northeast quarter, 2000 pounds on the southeast and north- 

 west quarters and 4000 pounds on the southwest quarter. Plot 7 received no 

 limestone on its northeast quarter, 500 pounds per acre on the southeast and 

 northwest quarters and 1000 pounds on its southwest quarter. Plot 6 was 

 given 2000 pounds per acre on its east half and 4000 pounds on its west half. 

 Plot 8 received one-half as much limestone as Plot 6. Table 6 gives the ar- 

 rangement of the liming. 



Table 6. — Pounds per Acre of Limestone Applied in 1923 



Plot 



Form of 

 Nitrogen 



Southwest 



Northwest 



Southeast 



Northeast 



5 Ammonia 4,000 



6 Ammonia 4,000 



7 None 1,000 



8 Ammonia 2,000 



9 None 4,000 



10 Dry fish 4,000 



The corn crop of 1923 was more nearly uniform throughout the plots than 

 that of the year before. The yields were not as large, which is often observed 

 when corn is planted for the second season after turning under sodland. 



Table 7 shows the weights per quarter-plots in 1923. The southwest quar- 

 ters of Plots 5 and 6 had regained much of their productive power. 



The crop yields of 1924, 1925, and 1926 showed that Plots 5 and 6 had 

 completely recovered from the toxic influence apparent in 1922. 



