1042 Summary of Agricultural Experiments, [march, 



trials at Ridgmont show that the value of the fruit obtained from dwarf 

 apple-trees grown in grass was only 7 per cent, of that obtained from 

 trees grown in cultivated ground exactly similar in all other respects. 

 It is, however, pointed out that the majority of the trials were so 

 planned that the effect of the grass would be exercised to a maximum 

 extent — the trees were young, and the grass did not spread gradually 

 over the ground, but seed was sown (or turf replaced) immediately 

 after the tree had been planted. Where the grassing over proceeds 

 gradually, the trees apparently accommodate themselves to the altering 

 conditions, and suffer much less than when the grass is actually sown 

 over their roots. The fact that a tree has become well established 

 in the ground before the land is grassed does not, however, prevent 

 it suffering. 



Standards on the free stock and dwarfs on the paradise were almost 

 equally affected, though some varieties of apple were less affected than 

 others, owing, doubtless, to their vigour of growth. Pears, plums, 

 and cherries were also affected, though in the case of these trees the 

 standards suffered less than the dwarfs. 



One of the most striking facts is that the action became noticeable 

 as soon as any of the roots of the tree had entered a grassed area, 

 no matter how small was the proportion of such roots to the whole 

 root system of the tree. 



It is suggested that in some soils, where the effect produced is not 

 great, grass might be advantageous from a commercial point of view, 

 for the check given to growth tends to increase the cropping, and 

 grass affects the colouring matter of all parts of the tree, generally 

 resulting in a high colouring of the fruit. 



Forest trees appeared to be affected by grass in the same way as 

 fruit trees when grass was sown immediately after planting, though 

 in the case of conifers on a light soil the effect was much less than 

 with other trees, and some recovery gradually took place. 



Explanation of the Effect. — The most commonly accepted explana- 

 tion is that the tree roots suffer from the competition of the strong and 

 widely searching grass roots, in obtaining moisture and plant food, 

 particularly the former. The writers of the report are, however, 

 unable to accept this solution, and give full accounts of experiments 

 designed to test it. 



Their findings and arguments may be summarised as follows : — 

 1. The effect of grass is pronounced in wet seasons as well as in 

 dry ones. 



2. Trees which are affected show none of the characteristic signs 

 of suffering from drought; and, in fact, in a time of drought the 

 grass shows the effect much sooner than the trees. 



3. The difference between the foliage of trees grown on cultivated 

 soils and that of those grown on grass is most marked in autumn 

 and spring, when there is plenty of moisture in the soil. 



4. Determinations of the water content of soils, in which trees 

 were suffering from the effect of grass, did not show lack of moisture 

 as compared with cultivated soils ; in fact, rather the reverse. 



5. Affected trees artificially watered still continued to show the 

 effect of the grass, even when the grass roots were prevented from coming 

 into contact with those of the tree. 



