FAEMEES' IXSTITUTES. 351 



repute amon.f,^ the ancient Romans, and is still practiced in Italy. Its benefits 

 must be marked, or it would not thus be retained in use through long genera- 

 tions. Its beneficial influence has been equally felt in other countries of Europe. 

 By its use the light sands of Belgium have been transformed into tbe most fer- 

 tile soil of Europe. In that thrifty country not a weed or bush is allowed to go 

 to waste ; every green thing not used for food finds its way into the soil to enrich 

 it. The wayside and hedges are gleaned for manure. ' 



la this country green manuring is in large use; but I believe it is not as 

 extensively practiced as it should be, mainly perhaps from certain theoretical 

 views in regard to its nature and effects ; and it is mainly to correct these theo- 

 retical notions, and to point out how it acts beneficially, that I bring the subject 

 to your attention. AVhen we see clearly how and why anything acts beneficially, 

 we are in better condition to secure that benefit. Besides this, there is a cer- 

 tain satisfaction in understanding the forces with which we have to deal. When 

 the brain is busy the hands are less weaiy. 



One reason why farmers undervalue green manuring is that "it adds nothing 

 to the soil but what it took from the soil ; " to take away a certain material and 

 return the same will not increase the sum total. I might reply to this, how can 

 you explain the influence of a clover sod in increasing the yield of wheat? If 

 the clover adds nothing to the soil, why does wheat grow so much better on such 

 sod? In assuming that the manural crop adds nothing to the soil, we forget 

 the large amount of food material which the plant has accumulated from the 

 air. The atmosphere is an inexhaustible storehouse of the combustible elements 

 of plant structure, and the air over any field is not a stationary mass, but is 

 changed by the winds every hour. The great bulk of vegetable material is 

 drawn directly from the air. The mineral elements come only from the soil, 

 but for the combustible elements the plant finds an exhaustless storehouse in 

 the atmosphere. "We thus find that the plant does give back to the soil more 

 than it took from it; it is an accumulator of atmospheric plant food. But if 

 the air is such a storehouse of plant food, why use any crop to accumulate this 

 plant food in the soil for the use of a succeeding crop? Is not the atmosjohere 

 an available storehouse for all kinds of plants? True; but different families 

 of plants differ greatly in their power of taking up this plant food from the air. 

 This is seen most distinctly in the different capacities of different families of 

 plants to accumulate nitrogen from the air. When I speak of combined nitro- 

 gen don't say, "that is scientific trash that does not concern me ; I don't want 

 combined nitrogen ; what I want is wheat ! " I once heard a witty farmer reply 

 to a professor who was talking learnedly about the nitrogen in crops, "Doctor, 

 if you will tell me how to raise twenty-six bushels of wheat to the acre, and do 

 it every time, I don't care whether there is an atom of nitrogen in it!" But 

 you cannot have the wheat without nitrogen. The very materials which elevate 

 wheat above every other kind of vegetable food cannot exist without nitrogen. 

 We can "make brick without straw," but the wheat plant cannot form the 

 berry without nitrogeu. The masterly researches of Lawes and Gilbert have 

 demonstrated the great importance of an adequate supply of combined nitrogen 

 for the production of wheat. It is the imperative demand of high farming in 

 the production of cereal grains. 



While all plants are capable of drawing a certain amount of required nitro- 

 gen from the air, they differ greatly in this respect ; one class, characterized by 

 broad leaves and abundant foliage, are capable of drawing almost the whole of 

 their nitrogen from the air and leaving a surplus in their remains for the wants 



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