44 



FUNDAMENTALS OF FRUIT PRODUCTION 



believe that its importance in that connection has been overemphasized 

 often. 



Table 25. — Rate of Growth of Different Crops from Aug. 25 to Oct. 2" 

 (Height in inches) 



Aug. 25 



Sept. 3 



Sept. 15 



Sept. 23 Oct. 2 



Cowpeas 



Soy beans 



Crimson clover 

 Hairy vetch . . . 



Oats 



Canada peas. . 



Rye 



Rape 



Turnip 



Millet 



3.0 



10.0 

 8.0 

 3.0 

 4.5 



11.0 

 8.0 

 8.0 

 4.0 

 4.0 

 5.0 



12.0 

 13.0 



3.5 



5.0 

 16.0 

 13.0 



9.0 

 10.0 



7.0 

 11.0 



14.0 



14.5 



4.0 



5.5 



18.0 



20.0 



10.0 



14.0 



8.0 



12.0 



20.0 

 22.0 

 6.0 

 8.0 

 24.0 

 24.0 

 12.0 

 16.0 

 12.0 

 18.0 



Winter-killed and Winter-surviving Cover Crops. — Cover crops are 

 generally classed as leguminous and non-leguminous when considered 

 in relation to their influence upon soil productivity. Emerson suggests 

 that when they are being considered as they influence soil moisture a 

 better classification would be winter-killed and winter-surviving.**' The 

 degree of cold actually experienced in a particular section determines 

 whether a given crop is killed by or survives the winter. Hence, a crop 

 that belongs in the one class in one place may fall in the other in some 

 other section. Any cover crop that survives the winter and resumes 

 active growth draws upon the moisture supply of the soil in the spring 

 and will continue to do so until plowed under or until cultivation of some 

 kind is begun. Since it is generally considered inadvisable to -plow or 

 cultivate deeply while trees are in bloom or the fruit is setting and since 

 soil moisture conditions and the press of other work often make the 

 plowing of the orchard before blossoming impracticable, cultivation is of ten 

 not begun until late in May or early in June. This gives a winter-sur-' 

 viving cover crop an opportunity to make considerable growth in the 

 spring, often more than it was able to make the previous fall. The 

 general effect of this growth upon soil moisture is shown by the figures in 

 Table 26 and is presented graphically in Fig. 2. By June 3 the winter- 

 surviving cover crop had reduced the soil moisture to approximately 

 half the amount in the soil protected by a winter-killed crop. In fact it 

 had consumed practically all the available moisture, leaving the water 

 content of the soil but Httle above its wilting coefficient. In regions of 

 comparatively high rainfall during the spring months, this waiter loss due 

 to the growth of winter-surviving cover crops would be of secondary 

 importance and it would likewise be unimportant in sections with 



