122 AGRICULTURE OF MAINE. 



{b) Experiments in Orchards of Early Bearing Age. 



The results in this group of experiments are somewhat less 

 clear and less uniform in their trend than those in the other 

 orchards. In general, however, the following points have been 

 fairly well demonstrated : 



(7) In the group of early-bearing or "adolescent" orchards, 

 the treatment involving sod alone has resulted uniformly in the 

 least growth and the most highly colored fruit of any of the 

 treatments. It also has usually exerted some stimulating influ- 

 ence on the yields. The latter effect is apparently secured pri- 

 marily as a result of mild injury while the former is probably 

 chiefly due to the hastening of maturity. The growth of gtass 

 directly over tree roots is usually objectionable because it offers 

 an undesirable competition for soil nitrates and moisture. 



(8) This competition can be satisfactorily eliminated by 

 means of a good mulch, — one involving about three tons of veg- 

 etation per acre annually, or once in two or three years on the 

 younger trees. The addition of such a mulch to the ordinary 

 sod treatment has increased the average yields by about 20 to 

 35 bushels per acre annually in the younger orchards, and it has 

 given a maximum annual gain of 76 bushels in one of the older 

 orchards. i 



(9) Assuming that the above gains represent the approxi- 

 mate crop value of a three-ton mulch, it is evident that relatively 

 cheap materials must be available, if the mulch is to show a 

 definite profit. A rye cover crop grown between the rows will 

 usually give a very satisfactory initial mulch around the trees, 

 and this can then be maintained for a considerable period by 

 growing leguminous or other less active permanent covers in 

 the unmulched areas. 



(10) In the "adolescent" orchards, the addition of fertiliza- 

 tion, with manure especially, has generally resulted in smaller 

 increases on the mulched areas than on the other treatments. 

 This condition is reversed in the older orchards, however, thus 

 indicating that the apparent interference in the younger or- 

 chards may be due to too thick a mulch. In general the mulch 

 treatment has compared very favorably with the other treat- 

 ments in nearly every point considered, but ample protection 

 again.st mice must be provided, wherever this treatment is used. 



