HORTICULTURAL RESEARCH 



III. THE ACTION OF GRASS ON TREES 



By SPENCER PICKERING, F.R.S. 



Conspicuous among the results obtained at the Woburn Experi- 

 mental Fruit Farm are those relating to the effects produced by 

 growing grass above the roots of fruit trees. From the economic 

 point of view the question is naturally one of considerable 

 importance to the fruit grower but it presents a still more 

 important aspect in its bearing on the fundamental problems 

 of soil-fertility and the effect which one crop has on another. 

 The mere fact that if grass be grown above the roots of fruit 

 trees it has a deleterious effect seems to have been acknowledged 

 previously by some growers, though it was denied, indeed, 

 is still denied, by others. The chief reason for this divergence 

 of opinion lies, no doubt, in the fact that the effect produced by 

 grass varies greatly according to the nature of the soil and, 

 in some few cases, may even be negligible : in practice also the 

 grassing of land under fruit is generally carried out gradually, 

 a form of treatment which materially reduces the evil effects ; 

 moreover, grassing is hardly ever practised in such a way that 

 the grower has an opportunity of estimating by compara- 

 tive trials what the effect has really been. 



In the case of many soils, when the grassing is done so as to 

 secure the maximum effect — for instance, when young trees are 

 planted either in land already grassed or in land which is laid 

 down to grass at once after the planting — the effect is practi- 

 cally always a fatal one. Fig. i shows two rows of standard 

 apple trees which were strictly similar at the time of planting ; 

 the one was grown in ground which was kept tilled, the other 

 in ground which was sown with grass after the trees were 

 planted and kept under grass. As will be seen, the result of 

 this difference in treatment has been to arrest practically all 

 growth. Another illustration is given in fig. 2 of similar dwarf 

 apple trees treated in the same way; the photographs in this 

 case were taken six years after the trees had been planted. The 



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