- 9 



Conclusion . Mixing lime with the soil used in the planting hole 

 for apple trees enhanced Ca levels for 2 years. Although the pH 

 of this soil was high and/or lime was incorporated in the soil, 

 leaf Ca was still relatively low, further emphasing the difficulty 

 of increasing the amount of this element in apple trees. 



The effect of soil applications of 3 sources of nitrogen on leaf 

 nitrogen (N), potassium (K), calcium (Ca) and magnesium (Mg) of 

 Sturdy Spur Delicious trees. 



Year Treatment Element (% of the dried weight) 

 N K Ca Mg 



1972 Potassium nitrate 2.32a^ 0.98a 0.97a 0.40a 

 Ammonium nitrate 2.34a 1.01a 1.02a 0.39a 

 Calcium nitrate 2.33a 0.93a 1.07a 0.41a 



1973 Potassium nitrate 2.48a 1.63b 0.74a 0.26a 

 Ammonium nitrate 2.49a 1.76a 0.79a 0.25ab 

 Calcium nitrate 2.52a 1.71ab 0.77a 0.24b 



^Means for an individual year, within a column, followed by a dif- 

 ferent letter are significantly different at the 5% level. 



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POMOLOGICAL PARAGRAPH 



Elimination of Sod with Herbicides . At our New England Fruit Meet- 

 ings, the panel on size-control rootstocks expressed concern about 

 complete elimination of sod under fruit trees with herbicides. 

 With no snow cover, a soil free of grass and weeds might expose 

 fruit trees to a deep soil freeze and root injury. Our experience 

 using paraquat plus simazine, dalapon alone or in combination with 

 simazine has shown that complete control of perennial grasses and 

 broadleaf weeds is unlikely when herbicides are applied at recom- 

 mended rates. In addition, annual grassy and broadleaf weeds gen- 

 erally invade the herbicide-treated areas, and by late summer the 

 weed population frequently is as dense as under trees that had been 

 cultivated until early July. At our Horticultural Research Center, 

 when we purposely applied excessive amounts of herbicides, not only 

 was the soil free of weeds, but soil erosion occurred which exposed 

 tree roots. Under these conditions, increased winter injury might 

 well occur. 



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