79 



interference would hinder the proper development and prevent the 

 proper work of roots. The muffler of mulch which forms a part 

 of this system of orchard management would of course intensify the 

 deleterious effects of the sod in the above respect. 



Fourth. The soil temperature is lower in the sod-mulch plots 

 than in the tilled plots. It is possible that the harmful action of 

 grass on trees may be accounted for in part by the influence of the 

 sod on the temperature of the soil. During the summer of 1907 

 the soil temperatures were taken in the tilled and mulched plots 

 twice a day for 41 days at the depth of six and twelve inches and 

 under as nearly comparable conditions as circumstances would per- 

 mit. At both depths the difference was in favor of the tilled plot. 

 At six inches the difference was slight, being only one-third of a 

 degree but for the greater depth, twelve inches, the average in 

 favor of the tilled plot was degrees. It is not an assumption 

 to say that the higher temperature is most favorable to the growth 

 of the apple tree, for plant physiologists, soil physicists and bacter- 

 iologists agree that an increase in soil temperature is favorable to 

 plant growth. As one of them puts it, "The soil is a great factory 

 that has its production vastly increased as the temperature rises." 



Fifth. There are probably differences in the biological or 

 *'germ life" activities taking place in the soil. This is a matter upon 

 which I am not qualified to speak with certainty. But I know that 

 the men who are studying soils find that there are various kinds of 

 micro-organisms inhabiting the soil which have much to do with 

 the proper functioning of the roots that grow therein. The soil is 

 teeming with countless millions of living organisms which bring 

 about necessary changes of one kind and another in that soil ; with- 

 out them higher vegetation would not grow. Now the activities of 

 these beneficient organisms are dependent on soil conditions and 

 King tells us, in the quotation given above, that tillage induces a 

 strong growth of soil micro-organisms ; that it improves tilth so that 

 soil organisms may spread readily and widely ; and that it converts 

 the root zone into a commodious and sanitary living-place for the 

 soil organisms." 



Sixth. The grass may have a toxic or poisonous effect on apple 

 trees. At the Fifthieth Annual Meeting of the Western New York- 

 Horticultural Society the speaker gave an account of a series of pot 

 experiments which seemed to show that grass roots in some wav 

 poisoned peach trees s^rowing. The United States Department of 

 Agriculture has published a number of observations and experi- 

 ments to show that different plants growing in the same soil may 

 poison each other. 



I am able to give also the results of a most excellent series of 

 experiments planned and carried out on the Woburn Experimental 

 Farm in England. These experiments were planned to show the 

 effects of growing trees in grass, the latter to be used as a mulch. 

 The following gives the gist of the results of the experiments in 

 question : 



"As to the general effect produced by grass on young apple trees, 

 the results of the last few years have brought forward nothing 



