SOIL FERTILITY 



tion, the simplest test is to compress a handful, 

 then, opening the fingers, give it a light toss. 

 The compressed lump should show a light im- 

 pression of the fingers. When tossed to the 

 ground, it should fall all apart with the soil 

 grains adhering in masses too small to be called 

 lumps. If the soil is sticky, over wet, over heavy 

 (clayey), coarse, or over light so as to fall in 

 distinct grains (sandy), it will not answer the 

 test. 



A chemical test of the soil would give all the 

 elements it contained and their proportions, but 

 would not determine what portion of them is 

 available for plant food. To be so available, 

 there must first of all be a reasonable amount of 

 water. Root fibres can absorb no food except 

 as it is in solution in the tiny films of water sur- 

 rounding each infinitesimal particle that goes 

 to make up the little masses usually spoken 

 of as atoms of soil. This film moisture is 

 known technically as "hygroscopic moisture" to 

 distinguish it from the capillary water which is 

 held in the spaces between the soil particles by 

 capillary attraction, and which is of direct use 

 to the plant in carrying plant food from place to 

 place. This capillary water finds its reservoir in 

 the ^'ground water", which is the water that has 

 percolated through the soil until it reaches an 

 impervious layer, where it gathers to supply our 

 springs and wells. To return to the hygroscopic 

 moisture, where there is so small a quantity as 



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