432 BULLETIN No. 127. [August, 



though not from the same stock, was perceptibly better on this 

 type of soil. In a test of Early Ohio potatoes on the heavy loam 

 soil, planting* to a depth of five inches gave potatoes of a much 

 better quality than potatoes which were planted to a depth of 

 three inches. The same was true of Carman No. 3 planted on a 

 light sandy soil, but potatoes planted three inches deep and ridged 

 at the last cultivation were of poorer quality than those unridged. 

 This coincides with Gilmore's extensive work where he found that 

 about five inches depth showed a more uniform temperature dur- 

 ing the season than did other depths. 



7. Season and climate. Season and climate are undoubtedly 

 factors in determining quality, though whether they have an in- 

 fluence beyond that of giving the plant greater or less chance for 

 producing healthy, mature tubers, it is impossible to say. As po- 

 tatoes are known to have a very great range of altitude and lati- 

 tude when conditions of soil are right, we are inclined to think 

 that the latter is the only influence. 



8. Influence of fertilizers. The influence of fertilizers seems 

 to be primarily if not solely due to their aid in producing a normal 

 development of tubers. That is, the fertilizer applied must correct 

 abnormality by furnishing an element of fertility which is lacking 

 in the soil. An application of ordinary quantities of an essential 

 element which is already present in the soil in amounts necessary 

 to a normally fertile soil, probably has no marked effect either 

 upon the crop or its quality. 



Some writers have maintained that the use of potassium sul- 

 fate gives potatoes of better quality than are produced with the 

 use of potassium chlorid, but this conclusion is opposed by other 

 experiments. There is probably no ill effect from the use of or- 

 dinary amounts (100 to 500 lb.*) of potassium chlorid, even if 

 excessive use of chlorids is detrimental. 



The following table shows the general effect of fertilizers upon 

 quality. In an experiment planned primarily an soil fertility, 

 sodium nitrate was sown at the rate of 250 lb. to the acre over 

 the whole plot and potassium and phosphorus supplied as shown 

 in the table. The numbers here shown are the estimates of qual- 

 ity of all of the tubers produced by all of the plants of one row 

 running across all the plots. The variety used was Green Moun- 

 tain. The land was very poor in fertility although in excellent 



*Potatoes of excellent quality have been tested, which were grown with this rate of potas 

 sium chlorid but no comparisons were made with like amounts ot potassium sulfate. 



