CH. x] Value of Organic Matter 167 



Durham and Northumberland artificial fertilisers gave 

 considerably poorer yields than dung, or dung and 

 artificials^. Extreme cases arise where artificial fer- 

 tilisers are of practically no value while the organic 

 manures lead to considerable increases in crop : such 

 cases are not common in this country, but they are not 

 infrequent in subtropical conditions, as for example in 

 Madras, Java, etc. Here neither nitrates, phosphates 

 nor potash give appreciable crop increases while the oil 

 cake residues have considerable fertilising value-. 



Organic matter cannot be regarded as necessary for 

 plant nutrition however desirable it may be from the 

 point of view of soil management. Large crops of wheat, 

 barley, mangolds and grass are regularly grown at 

 Rothamsted on land wliich for 70 years has received no 

 organic manure and the crops show no signs of falling 

 off. A strict comparison was made by Hansen on a light 

 loam and on a sand at Askor (S. Jutland) where farm- 

 yard manure was compared with a dressing containing 

 equal amounts of nitrogen, potash and phosphates in 

 the form of artificials (nitrate of soda, superphosphate 

 and kainit) and almost always gave poorer results^. 



But if organic matter is not needed by the crop it 

 is commonly required by the soil: and experiments all 

 over the country have shown that the best economic 

 results are obtained by a judicious combination of 

 artificial fertilisers with organic manures. 



Farmyard manure. Farmyard manure consists of the 



1 Armstrong Coll. Bull. No. 10, 1915. 



^ See, for instance, Dr Barber's Report of the Samalkota Experiment 

 Station, 1912. 



^ Fr. Hansen and J. Hansen, Tidsskriftfor Landbrugets Planteavl, 1913, 

 XX. 345. 



