]^]^8 STATE BOARD OF AGRICULTURE 



THE TRIPOD OF AGRICULTURE. 



It will be observed that attention is given to only three manurial elements— 

 Nitrofjrn. PJioftphoric acid, and Potash. This list does not include al Ithe elements 

 contained in plants, ten others being found in all plants grown under natural condi- 

 tions. But these three are the most important in plant growth; a deficiency of any 

 one of them in the soil limits the action of all others, and the available amount of 

 them in the soil is soonest exhausted by cropping. So important are these that 

 they have appropriately been called the tripod of agricuJtvre. If they are present 

 in sufficient quantity and in available form, the other plant elements, in nearly all 

 soils of our State, are found in sufficient amount, and good crops are expected 

 unless unfavorable physical condition of the soil or season prevents. 



WHY FERTILIZATION IS REQUIRED. 



The virgin soil contains a certain amount of plant food in available form which 

 the plant uses in its growth. This may be called nature's deposit in the bank of 

 earth. By the decompositions and chemical changes constantly going on in the soil, 

 an additional amount of fertilizing material is brought into the active form year by 

 year and deposited in the same bank to be checked out by crops. The removal of 

 a crop from the soil takes away a portion of these elements of fertility. If no 

 more is removed than the portion set free by chemical changes in the soil, then the 

 land retains its fertility: but if more is taken off in the crop, and not restored by 

 additional deposits (manures), then the land is losing in fertility and the bank ac- 

 count approaches the ledger entry, "No available assets," and nature protests the 

 farmer's draft for remunerative crops. 



A glance at the amount and kind of manurial materials removed by crops may 

 make this subject clearer. 



I 

 AMOUNT OF ASH MATERIALS REMOVED BY ONE TON OF DRY CROPS. 



Straw and fodder: 



Pounds 



Wheat straw 108 



Oat straw 106 



Cornstalks HO 



Timothy hay 142 



Clover hay 134 



Grains : 



Wheat 40 



Oats 66 



Corn 30 



Tubers: 



Potatoes (dry) 82 



Sugar beets (dry •' 88 



Field beets (dry) 154 



Tops and waste: 



Potato tops (dry) 102 



Sugar beet tops (dry) 350 



Field beet tops (dry) 364 



Field turnip tops (dry) 310 



Nitrogen, not being an ash element, is not included in this table; it is an organic 

 element and escapes when the plant is burned. 



The large amount of ash material removed in the coarser products of the farm- 

 straw, stalks, hay and tops of tubers--in comparison with grain, will command 

 attention, the one low in price but rich in ash, the other high priced and low in 

 ash. 



