FARMYARD MANURE 327 



ingredients it contains and the state of combination in 

 which they are present. 



Mechanical Effects. The characteristic and highly 

 beneficial effects of farmyard manure upon the texture 

 of soils are due to the organic matter, of which it ordin- 

 arily contains about 20 per cent, in the wet condition. 

 It helps to floculate clay soils and reduce them to a state 

 of tilth which in some cases cannot be produced hy any 

 other means. On sandy soils it has just the opposite 

 effect ; it binds them together and greatly increases their 

 power "of retaining moisture. Its effects are, for this 

 reason, often seen to greatest advantage in droughty 

 seasons, which are in other respects the least favourable 

 to its action. The mechanical effects of farmyard manure 

 are perhaps not less important than those which depend 

 upon its chemical composition, and, on this account, 

 it is considered by many to be practically indispensable. 

 If it is not produced or cannot be obtained in sufficient 

 quantity to maintain the necessary supply of humus in 

 the soil, recourse must be had to green manures, and 

 the supply of plant foods can be supplemented by special 

 concentrated fertilisers. 



The Fertilising Ingredients. The fertilising effects of 

 farmyard manure are particularly striking when regarded 

 from the point of view of its chemical composition. It 

 is a general manure containing nitrogen, phosphoric 

 acid and potash, but the proportions of these ingredients 

 are small generally less than one per cent, of each. If 

 the manure were used in handfuls or hundredweights the 

 quantities of these constituents would indeed be insig- 

 nificant, but when the quantities commonly applied are 

 taken into account, the matter assumes a different aspect. 

 An ordinary dressing of say 10 tons per acre of good 

 manure would supply about 150 Ibs. of nitrogen, 100 Ibs. 

 of potash and 60 Ibs. of phosphoric acid, To obtain 



