in cans between sprinklers in the field, appears to be adequate for a minimum 

 temperature of 20°F. 



Most of the rotary irrigation sprinklers used in Michigan, especially 

 those with two or more nozzles, usually apply more water than is needed for 

 frost protection. Some growers plug one nozzle and use only the nozzle with 

 the "kicker arm"; by use of this procedure, usually about half the normal 

 amount of water is applied. It may also be necessary to use a smaller-size 

 sprinkler nozzle to further reduce the application rate. Increasing the pres- 

 sure at the sprinkler will increase the wetted area and may create finer 

 water droplets, both of which are desirable. Your irrigation equipment 

 dealer can help you select the proper size nozzle and adjust the sprinkler 

 spacing. 



The turning and speed of the sprinklers can be an important factor in 

 the effectiveness of irrigation for frost protection. Small, one-nozzle 

 sprinklers turning one revolution in 12-20 seconds have given very satisfac- 

 tory results; whereas somewhat larger sprinklers with one nozzle plugged, 

 turning one revolution in 90 seconds or more, did not adequately protect a 

 tomato crop against a 24 degree frost. Until further research evidence is 

 available, definite recommendations regarding the turning speed of sprinklers 

 cannot be made. The rotation speed of some sprinklers can be increased by 

 increasing the spring tension or by making other adjustments." 



W. J. Lord 



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TIPS ON DETECTING MINER.\L DEFICIENCIES OF APPLE TREES 



Magnesium and potassium deficiencies are of frequent occurrence in 

 Massachusetts orchards. Both deficiencies are expressed by a scorching of 

 the foliage. Interveinal scorching of the foliage is generally associated 

 with magnesium deficiency while marginal scorching is characteristic of 

 potassium deficiency. However, in many cases interveinal scorching may 

 extend to the margin of the leaf making positive identification of the 

 deficiency difficult or impossible. 



A history of the fertilizer program used in the orchard where foliage 

 scorch appears will often aid in determining whether the scorch is due to 

 magnesium or potassium deficiency. For example, if scorched foliage occurs 

 in a block which has not been limed for several years and it has been fertil- 

 ized with a mixed fertilizer such as 10-10-10 you can be almost certain that 

 the scorched foliage is due to magnesium deficiency. On the otherhand, a 

 block which has been well limed and fertilized v^ith only a nitrogen carrying 

 fertilizer the scorched foliage will be an expression of potassium deficiency. 

 These observations have been verified by chemical analysis data which we have 

 obtained from growers orchards over the past several years. 



W. D. Weeks 



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