SOIL SESSION. 113 



longer rotation. The clover yields are a little larger in the shorter rota- 

 tion. 



Two series of plots in this experiment have been manured for each 

 corn crop with cattle manure, that used on the one series being manure 

 which had lain in an open barnyard for several months during the winter, 

 while that for the other series has been taken directly to the field from 

 box stalls, where it has been trampled under foot while accumulating. 

 If there has been any dilterence in the feed from which the manure was 

 made it has been in favor of the open yard manure. The manure has 

 been used in all cases at the rate of 8 tons per acre. It is spread on 

 the clover sod in the spring and plowed under. The wheat and clover 

 follow without any further manuring or fertilizing. 



Manure not only wastes by leaching when exposed to the weather, 

 but it is also subjected to heavy losses of ammonia when so managed that 

 heating and consequent chemical action take place. Moreover, the fact 

 tliat phosphatic fertilizers produce such a remarkable effect on many 

 soils which have been long in cultivation, indicates that ordinary farm 

 manure is either deficient in phosphorus, or that its phosphorus becomes 

 relatively less available to crops than its nitrogen and potassium. In 

 the hope of obtaining suggestions as to the practicability of diminishing 

 the loss of ammonia on the one hand, and of rendering the nitrogen and 

 potassium of the manure more effective by increasing the supply of 

 phosphorus on the other, the following treatment has been given to lots 

 of each kind of manure — yard and stall — since the beginning of this 

 experiment. 



One lot of each kind has been dusted with gypsum, or land plaster, 

 and another lot with kainit, a crude potash salt, these substances having 

 been shown to be useful in arresting escaping ammonia ; a third lot has 

 been treated with floats, the finely ground, phosphatic rock from which 

 acid phosphate is made by the addition of sulphuric acid, and a fourth 

 lot with acid phosphate itself, these materials being used on the as- 

 sumption that they would probably be as efficient as gypsum or kainit in 

 arresting ammonia, and would have the further advantage of re-enforc- 

 ing the manure with phosphorus. In the use of the floats a further 

 object was to learn whether this material, which is almost completely in- 

 soluble in its ordinary condition, might not be rendered soluble by the 

 fermentation of the manure, and thus obviate the necessity of treating 

 it with acid. 



These various materials have been applied to the manure in the 

 spring, usually in March or early in April, at the uniform rate of 40 



A -8 



