200 Fertilisers [pt, hi 



The medium grade contains 5 to 8 per cent, of nitrogen 

 and is considerably admixed with cotton, dirt and some- 

 times oil: larger supplies are available and it is much 

 used in hop gardens where it is ploughed in during 

 winter at the rate of 1-2 tons per acre. At Rothamsted 

 1 ton per acre has given good results on farm crops, and 

 the effect of the dressing even persists into the second 

 and third years (Table XVII). 



The lowest grade is sometimes very poor, containing 

 only about 3 per cent, of nitrogen, and should only be 

 purchased when it can be had cheaply. 



Acidulated or dissolved shoddy is prepared by treat- 

 ing shoddy with sulphuric acid in such a way that most 

 of the fibre is destroyed ; it is sometimes used on heavy 

 soils under the name of "organic meal," and also as a 

 base in the manufacture of compound fertilisers. 



Other waste products'^. From time to time various 

 nitrogenous or phosphatic substances are available as 

 manure and can be purchased at fairly cheap rates. 

 Their value depends on their composition, freedom from 

 toxic substances, and mechanical condition : they should 

 therefore only be purchased on analysis. The proper 

 way of dealing with them would be to submit them to a 

 preparatory grinding and mixing, but often the supplies 

 are too small or too irregular to justify the erection of 

 plant for the purpose. 



Hair, calf hair, etc., contains about 10 per cent, of 

 nitrogen but is very slow to decompose in the soil 

 especially in its usual long state: it should be only 

 used when it can be obtained very cheaply and is in 

 fair mechanical condition. 



Feathers containing about 9 per cent, of nitrogen are 



* Described in more detail in Board of Agric. Leaflet, No. 175. 



