128 



TABLE III. 



Influence of Covercrops on Tree Growth 



(Average Increases in Trunk-girth, 1908-13, the first 6 yrs. 



Expt. 333) 



Here again the mulched and untilled trees of the alfalfa 

 plat are distinctly in the lead. In fact their actual increases 

 are the greatest of any trees in the entire experimental 

 orchard of 33 acres. And this is accomplished without the 

 addition of any outside materials whatever and by means 

 of a plant that has been widely stated to be injurious to 

 apple trees. The latter might possibly be the case where 

 the roots are allowed to compete too freely, but where this 

 is prevented as in the present case, the results are all that 

 could be desired. 



Among the annual covers the vetch has given the best 

 per cent of gain. It is a leguminous plant, of very low 

 moisture draft owing to its hairy or woolly covering, and of 

 a spreading and matted habit of growth which largely pre- 

 vents direct evaporation from the soil. It is therefore not 

 surprising that its trees should show an exceptional growth. 

 Incidentally this plant is likely to be one of the best for a 

 permanent cover and as a basis for a mulch where it does 

 not winterkill too badly. Although naturally an annual, 

 it is being kept satisfactorily without re-sowing by means of 

 a thorough discing along in August or whenever a sufficient 

 amount of its own seeds have formed. This plan is now 

 working very well both in Virginia and in Southern Penn- 

 sylvania, and it is well worth trying farther north, especial- 

 ly on the lighter or sandier soils. 



