PREHAR\"EST APPLE DROP 



B. Chemical 



Since differences in root distribution due to dift'erences in soil 

 profile were not found definitely to cause the difference in behavior of 

 these trees with respect to dropping fruit, the probability of differ- 

 ences in soil pH and content of mineral elements was investigated. 



Acidity. Although the soil tended generally to be slightly more 

 acid under heavy-dropping trees, the differences do not seem large 

 enough to account for observed differences in drop (Table 6). It is 

 of interest to note that in the A and B zones the pH of the soil under 

 trees 58 and 88 was only 3.9 to 4.0. 



Table 6. pH of Soil 



L Light-dropping trees 



H Heavy-dropping trees 



Zones not present 



Chemical Elements. The available elements determined were: 

 nitrate nitrogen, ammonia nitrogen, phosphorus, aluminum, magne- 

 sium, potassium, and calcium. Table 7 shows that available nitrate 

 nitrogen was highest in the A zone and generally lacking in the D and 

 E zones. Ammonia nitrogen, on the other hand, was more evenly 

 distributed throughout the soil. The very slight difference in nitro- 

 gen content of the soil under light-and heavy-dropping trees did not 

 seem sufficient to account for the difference in apple drop. 



Table 7. Amount of Available Nutrients Present in Soil 



