CHAPTER XI 

 HUMUS. FARMYARD MANURE. LIME 



IT is evident that, in every single particular, experiments 

 should be made by the planter in order to determine 

 what method is best for the special soil and climate 

 where the cultivation is carried on, and in no respect 

 is this more necessary than with manures. The old 

 theory, founded on Liebig's teaching, that, having analysed 

 the plant and the soil, it was a simple matter of cal- 

 culation to find out what fertilizers to apply, is now 

 discredited. It is very difficult to estimate correctly 

 what proportion of any particular element in the soil is 

 actually " available " for the use of plants ; and again, it 

 does not follow that all the substances found in analysing 

 a plant are necessary to its well-being. The physical and 

 mechanical condition of soils appears to be more important 

 than the chemical composition. 



According to the Bulletin of the Bureau of Agricultural 

 Intelligence and of Plant Diseases for December 1912, 

 modern research into the physical properties of the soil 

 in different parts of the world leads to the conclusion that 

 in studying soil nutrients, the crude form of chemical and 

 mechanical analysis of air-dry soil does not give results 

 that are truly representative of the nutritive potentialities 

 of the soil investigated. For instance, liquids of different 

 composition can be obtained from the same soil by 

 pressure, washing (trituration), and leaching by rain ; and 

 it is held that in nature two soils of similar chemical com- 

 position may give rise to entirely different plant conditions 



65 ' E 



