SOIL MOISTURE 



59 



presumably more or less common. In this case plowing and cultivating 

 to a depth of 6 inches would have destroyed a little less than one-tenth 

 of the conducting roots. The percentage of the very small absorbing 

 and feeding roots would not necessarily be the same. Over 19,000 of 

 the total of 29,547 feet of conducting roots, in other words about 65 per 

 cent., lie beyond the spread of its branches. Probably the proportion 

 of feeding roots is still greater. Irrigation water and fertilizers should be 

 distributed accordingly; the treatment of the small area of soil immediately 

 surrounding a large bearing tree which is difficult of access with the tools 

 of cultivation would seem to be of small importance so far as either water 

 or nutrient supply is concerned. 



120 



iJ GO 

 +i 50 



I 2 3 4 5 e 1 8 9 10 II l^ \3 14 15 16 n 

 Dis+ance from Tree,feet 



Fig. 6. — Distribution of apple roots in surface six inches and second six inches in a 

 soil section one foot wide in rather heavy loam. Solid line shows surface layer; broken 

 line shows second layer. {After JonesJ^) 



In a Thin Gravelly Loam, Underlaid hy Rock, in Maine. — The data 

 given in Table 31 represent extreme conditions. They are for an under- 

 sized, stunted seedling apple tree probably 40 years old, on level ground 

 at the top of a hill thinly covered with a rocky, gravelly clay loam The 

 soil was less than a foot deep and was underlaid by rock or ledge or with a 

 heavy clay mixed with gravel. For many years the orchard had been in 

 pasture and the trees, having received practically no care, had experienced 

 a hard struggle for existence and many had died. 



Without doubt, limited nutrient as well as limited moisture supply had 

 been an important factor in forcing this tree to extend its root system so 

 far and wide in order to hold on in its struggle for existence. Whatever 

 may have been the exact combination of factors leading to this develop- 

 ment it shows a marked power of adaptation on the part of the plant. It 

 also carries the suggestion that in soils where deep rooting is impossible 

 the spacing of trees and other fruit plants should be much wider than 

 under more favorable conditions. 



