MIXED FERTILIZERS 45 



of hippuric acid secreted is much greater. Of the other 

 constituents of the urine the potassium occurs- as sulphate 

 and chloride, whilst sodium occurs as sodium chloride. 



The litter is a very important part of the manure heap. 

 Unless there is a generous supply of litter the beasts will 

 be uncomfortable and the valuable portion of the manure 

 will be lost by drainage. Most of the potassium and half 

 of the nitrogen occur in soluble form, which are only retained 

 by the absorptive capacity of the litter. The litter itself 

 may contain some nitrogen, phosphorus, and potassium, 

 but its chief value depends upon the water-absorbing 

 capacity. One part of leaves will absorb about two parts, 

 by weight, of water ; straw will hold three parts ; sawdust 

 four parts ; tan refuse five parts ; rough peat six parts ; 

 and picked peat-moss litter about ten parts. Some very 

 exceptional peat-moss litter may even hold eleven or twelve 

 times its weight of water without drainage. It is not practic- 

 able under ordinary conditions to get such good results 

 as these, because the trampling of the beasts will compress 

 the litter, and squeeze something out, but the relative values 

 of the materials will be roughly as stated. In practice much 

 will depend upon the relative cost of these different forms 

 of litter, but where practicable the more absorptive kinds 

 should be preferred, because it will save so much labour in 

 handling bulky useless material. How^ever a good deal of 

 the value of the manure depends upon its physical effect in the 

 soil, its provision of food for soil organisms, and its production 

 of carbon dioxide in the soil. It is not possible to la}'- down 

 any very strict rules on this subject. Straw will certainly 

 provide better food for soil organisms than most of the 

 other ingredients named. Sawdust appears to encourage 

 harmful organisms if large quantities of manure are used, 

 if it is badly distributed in the soil, and if the soil is wet 

 and compact. Admission of air to the soil is also an important 

 point in the value of farmyard manure, and for such a purpose 

 peat-moss litter will serve much better than any other member 

 of the series. It must also not be forgotten that the straw 

 might be used partly for feeding, as it would then not be 



