202 THE SYSTEM OF FAEM-YARD MANURING. 



rich in these constituents, the produce of straw depends 

 upon the quantity of K constituents in the ground : 

 hence the field which is richer in K, will, under like cir- 

 cumstances, give a larger crop of straw. 



The fact, therefore, that the fields at Cunnersdorf and 

 Oberbobritzsch yielded a hke amount of straw, cannot 

 lead to the inference that these fields contained an equal 

 quantity of S? constituents, since the corn crops show that 

 the quantities of K were unequal. The harvests exlii- 

 bited the following proportions : — 



In Cunnersdorf as . . . (11) K : (29) aK S^ 



„ Kotitzas .... (12) K : (30)aK S« 

 „ Oberbobritzscli as . . (14) K : (30) aK St 



As before remarked, the constituents represented by 

 the symbols K and St difier merely in this, that K com- 

 prises nitrogen and phosphoric acid, wliile the other con- 

 stituents of K are common to both ; hence the difference 

 in the corn crops of these three fields results mainly fi-om 

 the fact, that the roots of the corn found in the soil at 

 Kotitz -Jy and at Oberbobritzsch -^ more phosphoric 

 acid and nitrogen in an available condition than at 

 Cunnersdorf. 



If the question is asked, how much phosphoric acid 

 and nitrogen must be added to the field at Cunnersdorf in 

 order to make the crop of corn equal to that of Ober- 

 bobritzsch, it would be a mistake to suppose that an 

 increase of -fj would be sufficient ; for the augmenta- 

 tion of the produce of corn is materially influenced by 

 the St constituents, the quantity of which varies greatly 

 in different soils and has not been ascertained. 



By the addition of nitrogen and phosphoric acid, a 

 certain quantity of the accumidated St constituents are 

 rendered effective or available, which before were not so ; 

 but while the produce of straw increases, not ^, 



