144 EXPERIMENT STATION" EECOED. 



for Ohio conditions. The average girth of the trees in each of the remaining 

 plats and the average weight of apples secured are shown in the following table : 



The s/rotvth and yield of apple trees by different methods of culture. 



The table brings out the fact that the best results, as regards both growth and 

 yield of fruit, have been obtained by the sod-mulch method of culture. 



It has been claimed that in orchards receiving clean cultivation early in the 

 season, followed by a cover crop, the root system develops to a greater depth 

 and is consequently less injured by drought, heat, and cold than by the mulch 

 system. The authors examined numerous cubic-foot areas of soil from the dif- 

 ferent plats with reference to development of roots, examining first a 2-in. 

 layer, then the next 4 in., and finally tiie bottom G in., separately. " The main 

 root systems of apple trees, under the different methods of culture, were found 

 to be at a surprisingly uniform depth, the greater portion of the roots, both 

 large and minute, being removed with the upper 6 in. of soil." 



On the plat given clean culture, followed by cover crops, it was found that 

 thousands of feeding rootlets penetrate upward to the very surface of the soil, 

 where they actually come in contact with cultivator or harrow, while but very 

 few of these rootlets penetrate to the lower, more compact, colder soils. Each 

 season these feeding rootlets are cleanly pruned away by the plowshare, without 

 apparent injury to the trees or crops, since they have performed their function 

 and their places are occtipied the succeeding season by a new generation. 



A very dense network of feeding rootlets was also found on the surface of 

 the soil beneath the heavily mulched trees. These rootlets also penetrate the 

 lower layers of the mulch itself. There appeared to be, however, fully as many 

 feeding rootlets in the upper in. of the soil itself as was the case when the soil 

 was given clean cultivation throughout the early part of the season. It is held, 

 therefore, that since the main root system forms at as great a depth under the 

 mulch system as when the crop is given clean cultivation, and since the feeding 

 rootlets are just as numerous in the soil itself, the removal of the mulch, or 

 even a change from heavy mulching to the clean culture cover-crop plan, would 

 not be as disastrous as has been generally supposed. The destruction of the 

 surface rootlets and of those that penetrate the mulch, either by cold, drought, or 

 heat, is therefore no more serious a matter than is the destruction of the rootlets 

 in the clean cultivated soil l)y the plow. 



The authors state that " under the ' sod-mulch system ' of cultui'e the trees 

 have uniformly made a heavier, more vigorous growth than under any other 

 system of culture. This is no doubt due to the certainty and uniformity of 

 the generous store of fertility right at hand — the concentration of an abun- 

 dance of plant food where it is jnost available and the consequent presentation 

 of conditions, beneath the mulch of vegetable matter, especially favorable to a 

 healthy, unstinted, contimums nourishment of the ti-ees." 



Cover crops for young orchards, U. A. Emerson (Nchrasla t^ta. Bill. 92, pp. 

 1-23, pis. 2, figs. 8). — A sunnnary is here given of experiments which have been 

 carried on since 1899 in the use of cover crops in young orchards. Part of the 

 [lata here given have been previously noted (E. S. R., 14, p. 10G6). 



