THK TKXTL'RE OF Till: SOIL 43 



plant -food, nnd tbnt the rock contains a most aluindant supply 

 of potash nn<l about half as much phosphoric acid as the good 

 bean soil. 



"All this, after all, is not surprising, when we come to think 

 of it. Every good farmer knows that a hard and lumpy soil 

 will not grow good crops, no niatter how much plant -food it 

 may contain. A clay soil which has been prf)ducing good crops 

 for any number of years may be so seriously injured by one 

 injudic-ious plowing in a wet time as to ruin it for the grow- 

 ing of cn>ps for two or three years. The injury lies in the 

 modification of its physical structure, not in the lessening of its 

 plant -food. A sandy soil may also be seriously impaired for 

 the growing of any crop if the humus, or decaying organic 

 matter, is allowed to burn out of it. It then becomes leachy, 

 it quickly loses its moisture, nnd it becomes excessively hot 

 in briirht sunny weather. Similar rejnnrks may be applied to 

 all soils. That is, the texture ami sliuetnrr nr phi/xiral condition nf 

 the soti is netirlij always more important Ihtin its mere richness in 

 plant-food, 



"The first step in the enrichment i>f unproductive land is 

 to improve its physical condition by means of careful and 

 thorough tillage, by the addition of humus, nnd, perhaps, liy 

 under-drainage. It must first be put in such condition that plants 

 can grow in it. After that, the addition of chemical fertilizers 

 may pay by giving additional or redundant growth." 



53<i. Head Chapter ii. in King's "Soil." Tho following is 

 quote<i fn>m that work, p. 72 : "Suppose wo take a marble 

 exactly one inch in diameter. It will just slip inside a cube 

 one inch on a side, and will hold n film of water .'{.14U5 square 

 inches in area. But reduce the diametera of the marbles to one- 

 tenth of an inch, and at least 1,000 of them will l>o required to 

 fill the cubic inch, and their aggregate sarfnce area will be 

 31,416 square inches. If, howi»ver, the diamol< ' ' ' ,. s]>heres 

 be n'duced to one-hundre«lth of an inch. of them 



will \h> requin-d to make a cubic inch, '. surface 



area will then be 314. Ifi sqimre inches. ., the soil 



particles to have a diameter of oue-thousnndth of an inch. It 



