168 POMOLOGY 



They also report that, "The terminal twig growth has 

 been measured and found to correlate satisfactorily with 

 girth increase." 



At the Pennsylvania Experiment Station, a series of cul- 

 tural experiments was conducted in various parts of the 

 state, thus including various soil types. Table XLVI gives 

 the results of the treatment on the growth of the trees only, 

 as the effect on the yield is considered later. In two cases 

 the sod mulch system gave decidedly the best results in 

 growth, with tillage and cover-crops ranking second, tillage 

 (clean cultivation) third, and sod poorest. In the other 

 ten, the order of the first two is reversed and tillage and 

 cover-crops gave the best results by a very decided margin. It 

 seems that the younger trees respond best to the mulch sys- 

 tem and the older ones to tillage methods, while sod gives 

 poor results on all trees. 



The New Hampshire experiments again show the superi- 

 ority of tillage over sod. After ten years' work in renovat- 

 ing a declining Baldwin orchard, it was found that the 

 trees growing in sod made such inferior growth most sea- 

 sons as to make them less able to withstand the destructive 

 influences of weather and parasites. On the other hand, 

 tillage every other year resulted in a decided benefit to the 

 trees, but better results were obtained when tillage was 

 followed annually, amounting to 43 per cent greater than 

 when trees were grown in sod. However, the results of this 

 work are significant as they point to the conclusion that this 

 system (clean culture) could not be continued over a long 

 period of time on the soil involved, since at the end of ten 

 years the trees were not making so good an average growth 

 as at the end of the first five-year period, which is inter- 

 preted as a decline. 



When cover-crops were plowed in annually, there was an 

 additional 18 per cent increase in growth. However, under 



