disposal ; man has but a few short years and must work 

 rapid!}', and he cannot afford to make mistakes. 



9. The texture of the soil may be improved {^i) by luiderdrain- 

 ing (2) by tillivg (3) by adding vegetable matter (4) by addiyig cer- 

 tain materials, as lime, which tend to change the size of the soil parti- 

 cles. — The reader will say that Nature does not practice tile-drain- 

 ing. Perhaps not ; but then, she has more kinds of crops to 

 grow than the farmer has, and if she cannot raise oaks on a cer- 

 tain piece of land she can put in water-lilies. We shall have an 

 entire lesson devoted to drainage and tillage, and also one to 

 manures and fertilizers. It is enough for the present to say that 

 the roots which are left in the ground after the crop is harvested 

 are very valuable in improving the soil. This is particularly 

 true if they are tap-roots, — if they run deep into the soil. 

 Clover bores holes into the soil, letting in air, draining it, warm- 

 ing it and bringing up its plant-food. Roberts reports ("Fer- 

 tility of the Land," p. 345) that a second growth of clover, two 

 years from seeding, gave a yield of air-dried tops of 5,417 lbs. 

 per acre, and of air-dried roots 2,368 lbs. in the first eight inches 

 of soil. Add to this latter figure the weight of roots below 

 eight inches and the stubble and waste, and it is seen that the 

 amount of herbage left on the clover field is not greatly less than 

 that taken off. In this instance, the roots contained a greater 

 percentage of nitrogen and phosphoric acid than the tops, and 

 about the same percentage of potash. 



Make an estimate of what proportion of the plant growth 3-0U 

 raise is actually taken off the field. Figure up, as accurately as 

 you can, the portion left in roots, stubble, leaves, and refuse. 

 Even of maize, you do not remove all from the field. This cal- 

 culation will bring up the whole question of the kind of root- 

 system which each sort of plant has. Have you ever made a 

 close examination of the roots of potatoes, maize, wheat, clover, 

 cabbages, buckwheat, strawberries, Canada thistles, or other 

 crops ? From what part of the soil do these plants secure their 

 nourishment ? What power have they of going deep for water ? 

 What proportion of them is root ? Because the roots are hidden, 

 we have neglected to examine them. 



10. The soil is plant food ; but this food beco^nes usable or avail- 



