March, 1910,] 



203 



Miscellaneous' 



packed together tightly, as in pasture 

 land where the soil cannot be loos- 

 ened, there is comparatively little 

 space between the particles, and con- 

 sequently the amount of air in the soil 

 is but small. All grass land, as com- 

 pared with that under tillage, is in- 

 sufficiently aerated, and in most cases 

 the older the sod the less well ventilated 

 it is ; for, as time passes, the soil- 

 particles become more closely packed, 

 The ideal soil may be compared to a 

 sponge, not only because ot its capacity 

 for holding nutritive solutions, but 

 because of its permeability to air. There 

 can be no question that the high pro- 

 ductiveness of well-cultivated soils is 

 due largely to the greater amount of air 

 available for the roots. 



The presence of air ensures both 

 oxygen and carbonic acid in the soil. 

 Oxygen is essential to the growth and 

 well-being of the roots of plants, uo less 

 than to the serial parts. Carbonic acid 

 plays an important, though indirect, 

 part in ensuring soil fertility by bringing 

 inorganic materials into solution and 

 thus augmenting the supply of mineral 

 food-substances. 



Beneficial micro-organisms are found 

 in greater numbers and are better dis- 

 tributed in a cultivated soil than in 

 compact and uncultivated soils. These 

 lower forms of life, like the higher 

 forms, are profoundly affected, both as 

 to their individual well-being and as to 

 their multiplication, by such conditions 

 as food, air, moisture, and temperature, 

 all of which factors are better regulated 

 by cultivation. 



One of the objects of tillage is to 

 convert the soil into a suitable living 

 place for micro-organisms through the 

 increased humus, good drainage, ventil- 

 ation and higher temperature. It is not 

 unreasonable, therefore, to assume that 

 the greater number and better condition 

 of the micro-organisms in a tilled orchard 

 contributes to the well-being o*f the 

 fruit trees. 



There is evidence to show that all 

 plants, to a greater or less degree, so 

 change the soil in which they grow as to 

 make it wholly or partially unfit for a 

 succeeding crop of the same kind. 

 Different crops growing in the same soil 

 may injure each other, or the one the 

 other. Two theories are advanced to 

 explain these antagonisms of plants. 

 One is that plants excrete toxins ; the 

 other is that the injurious effect is the 

 result of bacterial activity. 



Mr. Spencer Pickering, of the Woburn 

 Experimental Fruit Farm, in account- 

 ing for the injurious effect of grass upon 

 young Apple trees, attributes the harm 

 done neither to competition between 



grass and treo for moisture and food 

 nor to a difference in temperature. He 

 holds that it is due, not to a lack of air 

 and oxygen, nor to excessive amounts of 

 carbonic acid, but to some " actively 

 malignant" effect on the trees, some 

 action on them akin to direct poisoning. 

 More recently, Mr. Pickering leaves the 

 question open as to whether the harmful 

 action is the effect of a poison (toxin) 

 excreted by the roots ,of the grass, or 

 whether it is the result of some change 

 in the activity or composition of the 

 miero-fl ji a brought about by the grass 

 sod. Beside these specific experiments 

 with Apple trees and grass there have 

 been recently several investigations 

 with other plants to show that vegetable 

 organisms have interdependences other 

 than those with their physical environ- 

 ment. For example, investigations with 

 Peach trees grown in pots with several 

 other plants show that the Peach does 

 not thrive if its roots are in close 

 proximity to those of certain other 

 plants. 



The well-being of nearly all plants 

 which miuister to the needs of man is 

 improved by tillage. Fruit trees not 

 only respond to high cultivation in the 

 nursery row, but they need good treat- 

 ment after transplantation to the 

 orchard. 



In experiments to determiue what are 

 the comparative effects of tillage and 

 grass sod on the Apple tree, it is found 

 that tillage is generally better than sod, 

 but it should not be expected, however, 

 that sod will be deleterious in the same 

 degree under all conditions. 



It is reasonable to suppose, for in- 

 stance, that in a deep soil, where the 

 Apple tree roots can escape from the 

 grass roots, or in one containing a great 

 amount of soil moisture, the harmful 

 effects of the grass will not be so marked 

 as in cases of an opposite nature. 

 Investigations do not show that the 

 Apples cannot be growu in sod. There 

 are many orchards which prove the 

 contrary. It is suggested, however, that 

 Apples thrive in sod, not because of the 

 sod, but in spite of it. The proof that 

 there are many thrifty orchards in grass 

 sod is not proof that these orchards 

 would not do better under tillage, 



The statement is often made that trees 

 will become adapted to grass. There is 

 nothing in the experiments conducted in 

 this country or in the Colonies to indi- 

 cate that such is the case. Trees planted 

 in sod begin to show ill-effects even in 

 the first year in which orchards are laid 

 down to grass, and each succeeding year 

 but adds to the injury. Trees can 

 hardly be expected to become adapted 

 to thirst, starvation, asphyxiation and 

 poisonous excretions. 



