63 



THE EFFECT OF GRASS ON TREES. 



The effect of grass on trees is probably intimately connected with 

 that fundamental question in agriculture to which no comprehensive 

 answer has yet been obtained, 'namely, the fertility of the soil. The 

 casual observer may dismiss the subject by stating that it is simply 

 due to the grass robbing the tree of its nourishment or its moisture, 

 but such a statement can only be based on ignorance of the facts, and 

 of all the work which has been done in the matter. The subject has 

 been under investigation at the Woburn Experimental Fruit Farm 

 for the last 15 years: one report (the third) dealing with it was 

 published in 1903, and it is hoped that another will be issued before 

 very long. 



Although no final solution of the problem has yet been obtained, 

 considerable progress has been made in the matter, and various 

 possible explanations have been definitely negatived. Foremost 

 amongst these is the theory that the action is due to the grass 

 absorbing all the food and water from the soil. The original experi- 

 ments are, perhaps, the most striking, though not the most precise, 

 on this point. A large number of Apple trees were planted in rows, 

 II feet apart, in 1904 : the ground in one row was kept tilled, and that 

 in the other row laid down to grass ; the grass, when cut, is left to rot 

 on the ground, and the same amount of manure is given to both rows 

 of trees. Those in the tilled soil are now such large trees that half of 

 them have had to be removed, their spread being some 15 to 16 feet ; 

 those in grass did not grow at all for several years, and only began 

 to make growth when their roots extended beyond the grassed area ; 

 they are still miserable specimens of trees, about one-sixth the size 

 of the others, and the crops borne by them have only been about one- 

 tenth of that of their neighbours. Yet the grassed soil is actually 

 richer than the tilled soil. In the 15 years it has had removed from 

 it only one crop of grass (that actually growing at any given moment) 

 and the small amount of material required for the stunted growth of 

 the trees ; whereas from the tilled soil there has been removed mate- 

 rial for an annual crop of fruit, and also for the vigorous growtK of 

 the trees. Analysis also shows that the grassed soil is the richer of 

 the two, and it also shows that, in this particular case, there is prac- 

 tically no difference between the water contents of the grassed 

 and open plots. 



Of the many other experiments on these points, the most 

 conclusive are, perhaps, those made with Apple trees grown in pots. 

 In some of these the grass roots were separated from the tree roots 

 by very fine wire gauze, through which the former could not pene- 

 trate ; the pots w^ere weighed and watered every two days, so as to 

 keep the water contents the same, and such water and food as 

 was added, was introduced from below, so that the tree should have 

 the first pull at it. Yet the trees still suffered badly from the grass, 

 although th e soil was actually moister and richer than in the case of 



