SOIL WASTAGE 9 



taken up soluble matter, may rise again to the surface bringing the 

 soluble matter up and leaving it at the surface on evaporation. Up 

 to a certain point this is favorable to the plant; beyond the critical 

 point, it begins to be harmful, as abundantly shown in the " alkaline " 

 efflorescences of arid regions. 



Besides the water that goes through the soil into the subdrainage, 

 and that which runs off on the surface, enough must be held at all 

 times in the soil during the growing season to supply the plants, and 

 yet not enough to water-log the soil. 



Here, then, are a series of possible excesses and deficiencies, between 

 which lie the golden means which give best results. The problem of 

 soil-management thus appears to be a problem of proper balancings 

 and adjustments. 



The key to the problem lies in due control of the water which falls 

 on each acre. This water is an asset of great possible value. It 

 should be the habit of every acre-owner to compute it as a possible 

 value, saved if turned where it will do good, lost if permitted to run 

 away, doubly lost if it carries also soil values and does destructive work 

 below. Let us repeat the story of its productive paths. A due por- 

 tion of the rainfall should go through the soil to its bottom to promote 

 soil-formation there; a due portion of this should go on into the under- 

 drainage, carrying away harmful matter; a due portion should go again 

 up to the surface carrying solutions needed by the plants; a due por- 

 tion should obviously go into the plants to nourish them; while still 

 another portion should run off the surface, carrying away a little of 

 the leached soil matter. There are a multitude of important details 

 in this complex of actions, but they must be passed by ; the great fea- 

 tures are clear and imperative. 



Experimental studies have shown that, on the average within our 

 domain, crops can use to profit all the rainfall during the growing 

 season, and much or all of that which can be carried over from the non- 

 growing seasons. This greatly simplifies the complex problem, for 

 the highest crop-values will usually be secured when the soil is made 

 to absorb as much of the rainfall and snowfall as practicable. There 

 are, of course, many local exceptions. In securing this maximum 

 absorption and internal soil-work, the run-off, and hence the surface 

 wash, will be reduced to a minimum. It has already been seen that 

 the wash of even this inevitable minimum is likely to be still too great 

 to keep the proper slow pace with soil-generation, when the surface has 

 much slope. Except on very level ground and on lodgment surfaces, 

 there need be no solicitude about a sufficient removal of the soil surface. 

 The practical problem then lies almost wholly in retaining and passing 

 into the soil the maximum of the precipitation. Obviously this gives 

 the minimum of wash to foul the streams, to spread over the bottom 



