8 MASS. EXPERIMENT STATION BULLETIN 450 



correlation coefficient between February sunshine and the Massachusetts crop 

 is evidence in support of these conclusions. Although the coefficient of .2211 

 ± .0916 is not very impressive, it actually represents a strong correlation ob- 

 scured by the fact that excessiA'e sunshine in February can contribute little to 

 the preparaiion of the crop; but scanty sunshine in this month will reduce the 

 crop by forcing the vines to draw upon their reserves of carbohydrates. Since 

 1893, a large crop has never followed a February in which the hours of sunshine 

 were 150 or less. 



Table 4 shows in detail the relation of the sunshine of the five significant 

 months mentioned above lo the size of Massachusetts Cranberry crops. 



Management Considerations 



It is a difficult matter to decide on the best procedure for any one bog. No 

 definite recommendations based on ihese weather studies are in order, the follow- 

 ing remarks being suggestions only. 



In May, when the vines are actively growing, it seems inadvisable to flood the 

 bog for a long period. Flooding waters greatly reduce the intensity of the sun- 

 shine reaching the vines and seriously restrict the amount of oxygen available 

 for respirction. Similar considerations are applicable to August, September, and 

 November, when sunshine is important to the building-up of reserves for winter 

 and the coming year. Though flooding in September and October is an important 

 cultural practice, the flooding period should be no longer than necessary. 



The obvious conclusion to be drawn from the February correlation is that the 

 flood should be withdrawn from under the ice during this month if heavy snow 

 cover or lack of normal sunlight reduces the oxygen content of the wati r. Before 

 this is done, the grower should consider the following: (1) the possibility of re- 

 placing the flood when the snow and ice cover melts; (?) the possible increase in 

 fruitworm infestation; and (3) the probable lessening of the spring frost hazard, 

 since vines exposed to low temperatures in the winter develop more slowly in 

 spring than vines that are protected by flooding waters all winter. Over 3500 

 acres of flooded bogs in Massachusetts had the flood withdrawn during January, 

 1948. 



Temperature and the Size of Massachusetts Cranberry Crops 



* 



Franklin^2 has set forth the more important temperature relations. He has 

 shown that low temperatures in March, Jul}', .September, and October of the 

 year of the crop favor the size of the crop. In relating temperatures in May to 

 the keeping quality of the coming crop, he has observed that high temperatures 

 in that month apparently tend to increase the size of the crop. 



May temperature of the crop year shows a correlation of -f- .2494 + .0903 with 

 size of crop, thus confirming Franklin's observation. This is the only month of 

 the crop year with a positive and significant temperature coefficienc. The rela- 

 tion of the mean temperature ot various groups of months in the crop year to the 

 size of the crop is set forth in Table 5. 



The correlation coefficient for March, — .2557 ± .0900, is slightly greater than 

 that for May, -f .2494 ± .0903. However, it is clear from Table 5 that the 

 addition of March temperatures to those of any other month or months lowers 

 the correlation coefficient of those months, while the addition of May tempera- 

 tures to those of any other month or months raises the coefficient. It would 

 appear, therefore, that May temperatures are more directly related to the size 

 of the crop than those of March. 



'2 Mass. Agr. Expt. Sta. Bui. 433, 1946. 



