lOI 



We find that the surface soil contains more phosphoric acid than 

 the sub-soil. 



We can understand why there should be more nitrogen in the 

 surface soil, for it is all of atmospheric origin, but we know that 

 the phosphoric acid or the lime or potash are derived from the 

 rock out of which the soil is made. The answer to this question 

 may be found evidently in the explanation that the roots of plants 

 go down into the sub-soil and bring up certain parts of the plant 

 foods found in the sub-soil. In other words, we must recognize 

 the fact that there is constant loss from all cultivated land or even 

 from land that is not cultivated, as well as gain. That is true of all 

 soils, but when land is placed under cultivation the losses exceed 

 the gains. When land is allowed to rest, allowed to be occupied 

 by vegetation, then the gains are greater than the losses and the 

 soil has time to become richer. 



We cannot maintain a satisfactory texture and likewise satis- 

 factory plant food conditions unless we provide for the mainten- 

 ance of a sufficient supply of vegetable matter in the soil. This can- 

 not be done unless animal manures are used or green manures are 

 employed. Commercial fertilizers are not sufficient. Hence the 

 significance of cover crops. First, cover crops will prevent the 

 washing out of soluble plant food. Second, cover crops will in- 

 crease the content of plant food in the surface soil, particularly 

 nitrogen. Third, cover crops will increase the content of vegetable 

 matter in the soil and will improve the water-holding power of the 

 soil. Fourth, cover crops will provide for a larger store of mois- 

 ture in all sections where snow falls and is likely to drift, and in 

 the case of orcharding cover crops have certain advantages which 

 they have not under other conditions of providing for the susten- 

 ance and growth of the fruit trees when that may seem desirable 

 to the fruit grower. I will discuss that at greater length presently, 

 because it is an important feature from the fruit grower's stand- 

 point. 



We need not discuss the loss of plant food at this time, per- 

 haps, nor need we discuss the moisture relations as modified by the 

 holding of snow. 



In the purchase of plant food we recognize that nitrogen is 

 an expensive constituent of commercial fertilizers. We also rec- 

 ognize that cultivated land, whether in orchards, fields or meadows, 

 may lose a considerable amount of nitrogen. That is, where soil 

 is cultivated, the loss may amount to 30, 40 or 60 lbs. a year. If 

 we are to restore that amount of nitrogen at a cost of 25c, there is 

 a value of $10.00 per acre that must be replaced. In cropping 

 methods or types of farming where the crop is worth a great deal, 

 $10.00 per acre would not mean very much, but even at that 

 it is likely to be an important item. We know from experiments 

 that have been carried on in most states, that the addition of nitro- 

 gen in cover crops may amount to as much as 100, 125 or 150 lbs. 

 per acre. By selecting a cover crop of the right quality we can dis- 



