472 INVESTIGATION BY CULTURE EXPERIMENTS 



The results of four years' tests as given in Table 91 are in com- 

 plete harmony with the information furnished by the chemical 

 composition of peat soil as compared with that of ordinary normal 

 soils. Where potassium was applied, the yield was from three to 

 four times as large as where nothing was applied. Where approxi- 

 mately equal money values of kainit and potassium chlorid were 

 applied, slightly greater yields were obtained with the potassium 

 chlorid, which, however, supplied about one third more potassium 

 than the kainit. On the other hand, either material furnished more 

 potassium than was required by the crops produced. 



The use of 700 pounds of sodium chlorid (common salt) produced 

 no appreciable increase over the best untreated plots, indicating 

 that where potassium is itself actually deficient, salts of other ele- 

 ments cannot take its place. 



Applications of two tons per acre of ground limestone produced 

 no increase in the corn crops, neither when applied alone nor in 

 combination with kainit, neither the first year nor the second. 



Reducing the application of kainit from 600 pounds to 300 

 pounds, for each two-year period, reduced the yield of corn from 

 164.5 to 125.9 bushels. The two applications of 300 pounds of 

 kainit furnished 60 pounds of potassium for the four years, or 

 sufficient for 84 bushels of corn (grain and stalks). The difference 

 between this and the 125.9 bushels obtained is 42 bushels, about 

 what was obtained from the poorest untreated plot. 



The underdrainage provided for this experiment field was not 

 sufficient for the best results, probably because of insufficient 

 nitrification. In other experiments on peaty soil with imperfect 

 drainage, the addition of $15 worth of nitrogen with potassium 

 produced about 15 bushels more corn than where potassium alone 

 was used. 



Peaty alkali soils. Aside from deep peat, there are many 

 other types of peaty soil, as will be seen from the classification of 

 Illinois soil types given in a previous chapter. Thus we find shallow 

 peat and medium peat, underlain with clay, sand, rock, etc., and 

 also sandy peat and peaty loam; and in some instances peaty 

 soils also contain alkali, consisting chiefly of harmless calcium car- 

 bonate with smaller amounts of injurious magnesium carbonate. 



In some cases these peaty soils actually contain a good percentage 



