New York AGRICULTURAL I.XPERIMENT STATION. ATE 
WHY TILLAGE IS BETTER THAN SOD FOR THE APPLE. 
The greater value of tillage in the Auchter orchard is con- 
clusively proved by the data given in the preceding pages. The 
question now arises. Why? What are the causes of the differ- 
ences that have been noted between the trees in sod and under 
tillage? These causes may be divided into two general groups: 
The beneficial effects of tillage; and the injurious effects of 
grass. It would be conducive to clearness if the causes might 
be discussed under the above heads but in few cases can the 
positive effects of tillage and the negative effects of grass be 
separated. Thus there is more moisture for the trees in the 
soil of the tilled plat because the tillage has conserved mois- 
ture and because the grass has removed that which would other- 
wise have gone to the trees in the sod plat. So, in general, the 
differences between the two plats in favor of tillage have been 
brought about by a good effect from tillage plus a bad effect 
from the grass. 
The tilled trees are better watered.—Liebig’s “law of the 
minimum,” according to which the yield of a given crop will 
be limited by the amount of one constituent of food, is now 
very generally applied to all of the factors atfecting the growth 
of plants. If applied to the possible factors that have pro- 
duced the results in this orchard it shows that one alone is 
quite sufficient to account for the differences noted—namely, 
the supply of water. 
The results of 120 moisture determinations in the Auchter 
orchard in 1907 and 1908 are shown in Table VIII. The 
weight per acre-foot, 48,560 square feet one foot deep, for a 
sandy loam, according to Hilgard,’ is approximately 1,800 tons. 
The average amounts of water in the soil at any time during 
‘the period of investigation are shown in Table IX. | 
Soils. By E. W. Hilgard, New York: 1906. p. 107. 
