- 12 



Occasionally, leaf analysis indicates that trees are low or deficient 

 in magnesium (Mg) (Table 1). The first indication of deficiency is a light 

 yellowing between veins of the leaf. When Mg deficiency is severe, browning 

 of the yellowed areas occurs. Usually, the more basal leaves are affected 

 first. For long-term correction of low or deficient Mg levels, apply dolo- 

 mitic limestone at the rate indicated by a soil test. For a more immediate 

 correction of Mg deficiency, a foliar spray of magnesium sulfate (Epsom 

 salts) is suggested in some peach growing ar.^as. The suggested rate is 10 

 pounds of Epsom salts per 100 gallons of water. 



Peach trees sre more sensitive to excessive applications of B than 

 apple trees, thus this element should be applied only in small amounts if 

 needed. Peach tree symptoms of excessive B are characterized by withering 

 and dying-back of terminal shoots during the growing season, the development 

 of cankers and gumming along the shoots, rough bark, prominent lenticels, 

 and excessive development of lateral shoots. To avoid B toxicity, Ernest G. 

 Christ, former Extension Specialist of Pomology at Rutgers University, is 

 very cautious about recommending the use of this element when fertilizing 

 peach trees. He states that. . . "fertilizer with 5 pounds of borax per ton 

 is usually OK for peaches. No additional B is ever needed or added. Also, 

 keep pH of soil 6 - 6.5." We suggest that peach growers in Massachusetts 

 follow the recommendations of Ernest Christ concerning use of B. 



***** 



UNDERSTANDING EFFECTS OF WEATHER ON APPLE YIELDS 



Wil 1 iam J. Bramlage 

 Department of Plant and Soil Sciences 



Year-to-year variations in fruit yield from an orchard are usually 

 accepted as a fact of life, but what are their underlying causes? J.E. 

 •Jackson and P.J.C. Hamer of the East Mailing Research Station, Kent, England 

 compared estimated yields of English 'Cox's Orange Pippin' apples with 

 weather records from 1949 to 1975 and came up with some interesting results 

 ( Journal of Horticultural Science s 55 : 1 49 - 1 56 ) . 



Over this time there was a steady increase in yield amounting to about 

 0.25 ton per hectare (about 7 bushels per acre). This steady increase was 

 attributed to technological changes in production practices, in particular 

 the use of better rootstocks and closer spacing of trees. This "technologi- 

 cal advancement" would amount to an extra yield of 180 bushels of apples per 

 acre in 1975 above the average yield in 1949. 



In addition to this steady increase in yield, 3 weather factors were 

 closely related to year-to-year variations. They were: (a) relatively high 

 temperature in February, March, and April; (b) relatively high temperature 

 immediately after full bloom (typically mid-Hay); and (c) relatively cold 

 weather in June. 



