120 FOOD OF PLANTS. 



the same crop, which requires a large amount of a given mate- 

 rial, it may require it faster than the circumstances of the case 

 can supply, and a crop that requires little or none of that mate- 

 rial may flourish. 



The supplying of the requisite materials in greater quantity 

 than nature furnishes them, is called manuring. This ordina- 

 rily is accomplished by applying refuse vegetable or animal 

 matter. Either or both of these, of course, would, by their de- 

 cay, afford the appropriate nourishment, as it is of the same 

 composition. Decaying vegetables of the same kind would, of 

 course, be the most appropriate food. 



219. To perfect the seed requires other elements than the 

 growth of the stalk. Nitrogenized substances are required for 

 this purpose, and these are especially afforded by animal ma- 

 nures ; hence these are the most highly esteemed for the raising 

 of grain. Wheat or other grains raised by nitrogenized sub- 

 stances are much richer in the nutritive elements for animals. 

 Guano supplies large quantities of ammonia; hence its impor- 

 tance in agriculture. Phosphates are also required to perfect 

 the seed ; hence pounded bones, which are phosphate of lime, 

 are highly esteemed. To render them soluble, however, sul- 

 phuric acid must be applied to them. Nitrogenized substances 

 are calculated especially to give vigor to vegetable growth ; 

 hence the gardener, when he wishes to produce double flowers, 

 supplies the plant abundantly with this kind of food, and the 

 stamens are converted into petals. But when the fruit is to be 

 forced into excessive development, the phosphates also must be 

 present. An abundant supply of both these materials produces 

 the most perfect development. Many articles are beneficially 

 applied to crops which do not act directly themselves. 



Gypsum acts by fixing the ammonia ; lime by liberating 

 other substances, and perhaps by stimulating the plant; and 

 so of many others. 



Fallowing, that is, raising green crops, and ploughing them 

 wholly or partially in, is a most excellent mode of furnishing 

 food for crops. 



220. Boussingault takes the following view of the subject. 

 He supposes a farm devoted to the cultivation of grain, possess- 

 ing, of course, a sufficient amount of stock. One knows by ex- 

 perience what quantity of manure is indispensable, therefore the 

 i 



What is manuring? How usually accomplished? — 219. To perfect the 

 seed, what is required? How is wheat affected by the soil? Why is 

 guano valuable? What of phosphates ? The combination of what mate- 

 rials produces the most perfect development? How does gypsum act I 

 How time? What is fallowing? — 220. Give Boussingault's illustration. 



