A Comparison of Yields. 505 



diagrams are given for these three factors for each of the species 

 chosen. Averaging these results by regions, the diameter growth 

 in 50 years is shown to be 112 per cent, greater in the southeast. 

 In height growth there is only a difference of 21% in favor of 

 the southeast. In number of trees, however, the northeast leads 

 by 164%. 



For corroborative evidence that the average yields in a given 

 time are greater in the northeast than in the southeast, the census 

 figures for the yields of agricultural crops were co^isulted. 

 These showed that the average yield per acre for corn in the 

 northeast was 186% greater, for wheat 97% greater, for pota- 

 toes 92% greater and 29% greater for hay. A comparison of 

 the yields in apples and peaches could not be made on an acreage 

 basis but was made on a basis of bearing trees. The figures 

 obtained in this way are subject to two interpretations. They 

 may indicate that the tree bearing the most fruit has reached 

 the greatest individual development in wood, leaf and fruit pro- 

 duction, or that the tree wnth the heaviest crop has come nearer 

 the optimum balance between wood and leaf production and fruit 

 which would seem to be caused by the same factors that produce 

 heavy yields in field crops. It is a well known fact that the big- 

 gest and fullest crowned fruit tree does not always produce the 

 most fruit and therefore the latter assumption seems the more 

 reasonable. Hence the yield of fruit per tree is cited along with 

 the other data on an acreage basis even though it is open to 

 question. The census figures showed that the yield per bearing 

 tree is 66% greater in the northeast for apples and 100% greater 

 for peaches. 



While it may be urged that the climatic factors are not the only 

 ones responsible for these differences in yields, the evidence fur- 

 nished by these data may fairly be taken as corroborative of the 

 conclusions reached from the study of tree growth. While it is 

 impossible to analyze the factors of yield in the case of agricul- 

 tural crops with the same nicety that can be done with tree crops 

 it is evident that the main difference lies not in the size of the 

 individual plants but in the density per acre and the amount of 

 fruit which each plant yieds. Probably the most striking example 

 of this which can be cited is the difference in practice in corn 

 planting in the two different regions. In the northeast the corn 

 is relatively short but several stalks are grown in each hill, while 



