172 



Journal of Agricultural Research 



Vol. XIII, No. 3 



MANURES USED 



In our study of organic crop residue as possibly contributory to the 

 development of acidity in these ammonium-sulphate plots we have used, 

 as the organic materials to be mixed with the soil, various green-manur- 

 ing plants, leguminous and nonleguminous, and some common weeds 

 and less desirable grasses. These have been used both fresh and air 

 dried with the thought that in the latter condition, while the plant mate- 

 rials would not have the exact balance of composition possessed by the 

 corresponding mature growths, they would at least resemble the mature 

 plants in physical quality and resistance to the bacterial penetrations. 

 To the list of organic materials used (Table I), barnyard and poultry 

 manures were added to ascertain what differences of behavior they might 

 develop, with the view of thus more sharply distinguishing the real 



factors. 



Table I. — Green manures used in experiments 



The wheat, rape, and soy beans used were young, tender plants. The 

 wheat was obtained from a pot experiment, where the growth was about 

 I foot high. The other materials were removed from the field on July 

 6, and they represented an average stage of maturity at that period. 



The composition of the several manures as used in Series I, with respect 

 to the point judged to be most important in the present study, is given 

 in Table II. 



