36 Experiment Station Bulletin 367 



FRUIT 



Leaf Scorch in Deciduous Fruit Plantings 



Large branches of Mcintosh trees susceptible to leaf scorch were in- 

 jected with magnesium nitrate. One gallon of a dilute solution was ab- 

 sorbed very quickly and resulted in burning the edges of the leaves. In 

 another block, known as the 35 Orchard, trees which had suffered annual- 

 ly from severe leaf scorch were selected for spraying tests. Certain 

 branches were sprayed whereas others were left as controls. Magnesium 

 nitrate and calcium nitrate were thus compared with relation to their ef- 

 fect on leaf scorch. Four sprays were given during the season. Ten per 

 cent solutions each of calcium nitrate and of magnesium nitrate caused 

 edge burning on the leaves, but 5 per cent solution sprayed on the 

 branches increased leaf scorch. 



The trees have been mulched for four years with either hay, dust, 

 or seaweed. The mulches have not as yet reduced leaf scorch, nor is 

 there any evidence that leaf scorch has been increased by such treat- 

 ments. 



Chemical analysis of leaves from the sprayed trees showed that 

 leaves of healthy trees were higher in both calcium and magnesium than 

 those of scorch-susceptible trees. After leaf scorch had appeared there 

 was no difference in the calcium content between non-scorched and 

 scorched leaves of the same trees, but the magnesium content of non- 

 scorched leaves was twice that of scorched leaves on the same tree. With 

 both healthy and scorched trees the calcium content of leaves rose 

 throughout the season until by October 1 the percentage of calcium in 

 these leaves was nearly twice the calcium content on the first of June. 

 The magnesium content of good leaves on both healthy and susceptible 

 trees remained practically constant throughout the growing season. 



Two crops of oats were grown on soil which was obtained beneath 

 scorch-susceptible Mcintosh trees. Neither lime nor magnesium in- 

 creased the growth or total weight of plants harvested over the control 

 plot which contained no lime and very little magnesium. Oats have re- 

 sponded differently from corn and turnips tried previously. 



L. P. Latimer, G. P. Percival 



Radioactive Phosphorus for the Study of Plant Nutrition 



A paper giving the results of previous work on the movement of 

 radioactive phosphorus during the winter has been prepared. Data 

 were collected by taking samples from plants fed radioactive phosphorus, 

 having them ashed by the Engineering Experiment Station at the Univer- 

 sity of New Hampshire, and the radioactivity determined by the Physics 

 Department of the Massachusetts Institute of Technology. An attempt 

 to use a portable Geiger-counter to determine when radioactive phos- 

 phorus had started to move up the tree has not given satisfactory results. 

 The concentration of radioactive phosphorus in the plants, when nutri- 

 tive solution of the proper dilution is used, is too small to be detected 

 with certainty by the direct application of the counter to tree trunks. 



