30 THE OLIVER PLOW BOOK 



Scientists tell us that wheat, oats, barley, rye, etc., 

 take up the nitrogen, which they use from the 

 roots, and then only in nitrates in dissolved form. Hence, 

 nitrogen must be available in the ground. 



The more nitrates there are in the ground per acre 

 the greater chance the farmer has of growing increased 

 crops. He may have his phosphorous, potassium, cal- 

 cium and water, but unless he has the nitrogen which 

 he can get from the free air, he can never grow the proper 

 kind of crop. 



Since the need for air in the soil is highly important it 

 behooves the plowman to be very careful to see that the 

 ground is thoroughly pulverized and that all large air 

 spaces are eliminated and the after preparation of the 

 seed bed made so as to keep the air and moisture mixed 

 in the ground in as nearly the perfect proportion as 

 possible. Enough has been said to show that the perfect 

 condition in all soils is when the soil has natural air 

 spaces between the soil particles. This is one reason 

 why Nature makes soil particles with irregular surfaces. 

 The best way for aerating the ground is to thoroughly 

 pulverize when plowing. To be sure of this requires a 

 study of the shapes and sizes of plow bottoms, because 

 different soils require different shapes, sizes and curva- 

 tures of bottoms to bring about the desired result. 

 Also the time of the year that the plowing is done with 

 relation to the time elapsing between the plowing and 

 planting has a great deal to do with the success of 

 this practice. 



In the chapter on the temperature of the soil atten- 

 tion is called to the difference in the temperature required 

 for the most propitious development of plant food and 

 the planting of wheat to resist the winter's freezing. 



