ORCHARD SOIL MANAGEMENT METHODS 



33 



nearly 4 per cent, difference in the respective subsoils. When it is con- 

 sidered that a part of the water in each case is unavailable for tree growth 

 because needed to supply the hygroscopic requirements of the soil, it is 

 evident that the tilled ground may contain many times as much available 

 moisture as the land in sod and that the difference between the two 

 methods of culture in respect to the available water is actually much 

 greater than the figures would suggest at first glance, The Pennsylvania 

 data presented in Table 19 show clearly that artificial mulching may be 

 and indeed usually is, a most efficient means of reducing evaporation. 

 They also throw some light on the effect of intercrops and cover crops 

 upon the water content of the soil, though no information is available as 

 to the season in which the determinations were made. Incidentally, 

 Table 19 shows how the soil-water supply influences the growth and the 

 yield of apple trees, though it should not be inferred that all the differences 

 in growth and yield are due directly to the variations in water supply. 

 It is significant, however, that there is a close correlation between the two. 



Table 18. — Soil-moisture Determinations in a Mature Apple Orchard in 



New York^^ 

 (Under different methods of soil management) 



