96 STATE BOARD OF AGRICULTURE. 



salts will also be prevented. Prof. Gulley tried this method at the college, 

 and stovitly aflBrmed that he got as active manure and twice the quantity by 

 composting with muck. 



When we come to look closely into the value of barn-yard manure, we find 

 that we are looking for potassium, phosphorus, and nitrogen after all. A 

 brief consideration of the composition of barn-yard manure will make this 

 plain. The portion of fodder that is not eaten, but only serves for litter, is 

 obviously of the same composition as the plant as it came from the field, and 

 contains all the materials for forming another similar plant. That which was 

 eaten and completely digested still retains all its manurial powers unimpaired, 

 so far as relates to the requirements of plant life. Digestion in its final result 

 simply strips from food the most of the carbon, oxygen, and hydrogen, while 

 all the other chemicals of Agriculture reappear undiminished in the animal 

 excrements in a more active form. We may say the material has been boiled 

 down by loosing the starch, sugar, gum, fats, etc. Thus even in the complex 

 material lumped off as barn-yard manure we are still in search of our golden 

 trio, and the manurial question resolves itself into this, where shall we 

 obtain in available form, in greatest quantity and at least cost, our potas- 

 sium, phosphorus, and nitrogen. On these points hang all the law and 

 profits of agriculture. 



GREEN MANURING. 



Another complete manure is found in the fresh vegetable matter of green 

 manuring. In this method the whole vegetable growth is returned to the soil, 

 and in a condition to insure rapid decomposition. In no other way can a soil 

 in poor condition be brought into good condition so rapidly and by so little 

 expenditure of money. By its skillful use the light and shifting sands of 

 Belgium have been made the most fruitful fields of Europe. 



A prejudice has arisen against green manuring which finds this expression : 

 "Green manuring gives back to the soil only what it has taken from the soil; 

 to take something from the soil, and to give back the same thing, cannot 

 increase the fertility of such soil." 



There is in most soils a large store of reserve material for plant food which 

 is in the inactive because insoluble form, but which may be made active by 

 any process by which it is made soluble. This may be accomplished by the 

 naked fallow, the frequent stirring of the soil, promoting chemical decomposi- 

 tion of these inert materials. But there are other and more rapid means. 

 Certain plants have a singular power of corroding these insoluble minerals by 

 the action of their roots, bringing these minerals into soluble form and using 

 them to build up their tissues. When such plants are plowed under the soil 

 they may give back to the soil only what they took from it, and yet add greatly 

 to its fertility, because they have transferred such minerals from the retired 

 to the active list. 



But it is not true that plants give back to the soil only what they have taken 

 from it. All plants take carbon from the air, and green manuring is the 

 easiest way to increase the store of humus in the soil. 



Certain classes of plants also have a singular power of accumulating com- 

 bined nitrogen. Where they get the whole of this combined nitrogen is at 

 present a mystery, but the fact that certain classes of plants do acquire a large 

 store of nitrogen where other classes of plants fail to secure such supply is 

 unquestionable. When these plants, rich in nitrogen, are plowed under the 

 soil, they give to the soil in active form something which they did not take 



