216 THE SYSTEM OF FARM-YAKD MANURING. 



depends of course upon the absorptive power of the 

 soil ; now, assuming, for the sake of illustration, the soil 

 of a field to be divided from the top downwards into 

 distinct layers, which are not of course sharply sepa- 

 rated from one another, we find that in some localities 

 the dung-constituents stop in the upper layers, whilst 

 in others they penetrate to the deeper layers of the 

 ground. Thus, for instance, in the Cunnersdorf field 

 the clover crop had derived no 1 benefit from the farm- 

 yard manure, being about only 4 per cent, larger than 

 the produce given by the urimanured plot ; whereas 

 at Mausegast the manuring caused an increase of 30 

 per cent., and at Oberbobritzsch of 200 per cent. This 

 result shows that certain mineral constituents, indispen- 

 sable for clover, penetrated much deeper into the 

 ground at Mausegast and Oberbobritzsch than at Cun- 

 nersdorf and Kotitz ; or, what comes to the same, that, 

 in the two latter places, they were, on their way down- 

 wards, retained by the upper layer of the soil. On 

 comparing the crops given by the unmanured plot at 

 Cunnersdorf with those obtained from the unmanured 

 plots in the other localities, we see that the Cunners- 

 dorf field contained nearly as large a store of straw 

 constituents as the fields at Kptitz and Oberbobritzsch, 

 while it was decidedly poorer in the principal grain 

 constituents, namely, in phosphoric acid and, perhaps, 

 also in nitrogen. Hence, with an equal supply of 

 phosphates and ammonia on the three fields, the top- 

 most layer of the ground at Cunnersdorf, being poorer 

 in these constituents, would retain a great deal more 

 of them than that of the other two fields. 



The increase in the potato crop and in the produce 

 of oat-grain and straw, on the Cunnersdorf field, clearly 

 indicates that certain dung-constituents made their way 

 to that layer of the soil from which the roots of the oat- 

 plant principally derive their food, which layer, being 

 richer in corn and straw constituents than the arable 

 surface soil, permitted a small proportion of nutritive 

 substances to pass through it and thus reach the clover. 



If we compare with this the field at Kotitz, and look 



