70 The Principles of Fruit-growing 



water-supply, (2) decreasing some elements in the food- 

 supply, (3) reducing the amount of humus, (4) lowering 

 the temperature of the soil, (5) diminishing the supply of 

 air, (6) affecting deleteriously the beneficial micro-flora, 

 (7) forming a toxic compound that affects the trees. 



"General statements are: Sod is less harmful in deep 

 than in shallow soils; there is nothing in this experiment 

 to show that apples ever become adapted to grass; sod 

 may occasionally be used in making more fruitful an 

 orchard growing too luxuriantly; other fruits than the 

 apple are probably harmed quite as much or more by sod; 

 the effects of grass occur regardless of variety, age of tree, 

 or cultural treatment, and are felt whether the trees are on 

 dwarf or standard stocks; because of their shallow root- 

 systems, dwarf trees are even more liable to injury from 

 grass than standards; hogs, sheep or cattle pastured on' 

 sodded orchards do not overcome the bad effects of the 

 grass; owners of sodded orchards often do not discover the 

 evil effects of the grass because they have no tilled trees 

 with which to make comparisons; it is only under highest 

 tillage that apple trees succeed in nurseries, and all the 

 evidence shows that they do not behave differently when 

 transplanted; grass left as a mulch in an orchard is bad 

 enough ; grass without the mulch is all but fatal it makes 

 the trees sterile and paralyzes their growth, and it is the 

 chief cause of unprofitable orchards hi New York." 



In New Hampshire, Gourley reports (Bull. No. 168) 

 that "The five-year average shows all methods of treat- 

 ment to be superior to growing trees in sod as regards 

 yield and size of fruit, and growth of tree. Cultivation 

 annually every two weeks until September 1 has given 

 results on yield and growth superior to cultivation every 

 other year, including a cover-crop the alternate years of 



