Converting and rectifying bacteria may be absent or dormant for 

 lack of oxygen or because of an acid soil. Lime neutralizes acid soil, 

 and tile and tillage ventilate it. If nitrogen is lacking, it can be sup- 

 plied by planting clover, alfalfa, cow peas or soy beans. 



Water is an essential factor in forming plant food compounds, and its 

 presence in sufficient quantities depends upon the methods used by the 

 farmer. In short, a sweet soil well stocked with air, water and manure, 

 and thoroughly tilled, will rarely fail to produce abundant crops. 



Rotation 



A well-arranged system of rotation of crops is a splendid means of 

 assistance in keeping the soil rich in some plant food and in a most 

 excellent physical condition. 



We know that if land is cropped year after year with the same kind of 

 crop that each succeeding year the crop is less. We also know that if 

 crops are rotated, that a greater yield is made. The farmer naturally 

 inquires why there is such a variation between continuous cropping and 

 the results of a system of rotation. 



While the same chemical elements enter into all farm crops, they differ 

 greatly in the quantities the various ones require. For instance, a 

 grain crop requires less potash than clover, potatoes or root crops; oats 

 take more potash from the soil than wheat or corn; likewise, clover 

 requires more phosphorus than grain crops. The requirements of 

 wheat, for instance are the same each year. Each crop calls for just 

 so much nitrogen, phosphorus and potash. The roots of each crop 

 penetrate the earth to a certain depth, taking plant food in the same 

 ratio and from the same strata of soil each year. 



Clover has different habits than corn, grain or roots. The roots 

 penetrate deep and their requirements are different. Clover, like other 

 legumes, consumes nitrogen, but gathers it from the air and deposits it 

 in the soil, leaving the soil richer in that plant food element than it was 

 before the crop was planted. The deep roots decay, forming humus 

 several feet deep and make available plant food beyond the reach of 

 many grain plants. The decaying roots place the soil in excellent 

 physical condition and hidden plant food thus formed is brought to the 

 seed-bed by capillary water and is consumed by succeeding ci ops. 



It is erroneous to believe that all the plant food exists in what we term 

 the "seed-bed"^ — that is, the first six or eight inches of soil. Fertility 

 extends many feet down and it can be utilized by resorting to a common 

 sense rotation and thorough tillage. 



How Plants Feed 



Plant food in a soluble state forms an envelope around each particle of 

 soil, and is taken up by root hairs and carried into the plant. Carbon 

 dioxide from the air is breathed into the plant through air valves in the 



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