Ji:ne, 1940] Experiments With Potatoes 37 



Double-strength fertilizer caused a significant increase in yield over 

 single strength on Lane farm, when equal amounts of plant food were 

 used. On the Lane farm banding the fertilizer along the sides of the row 

 gave a slight increase over broadcasting the fertilizer. 



Magnesium did not affect yields appreciably in either test. 



A limited amount of data with boron on Jackson farm does not seem 

 to warrant the use of this element at present on a soil with the history 

 of that of the Jackson farm field. 



Other Crops in Rotation 



Li these tests a three-year rotation of potatoes, oats, and mixed hay 

 w^as practiced on Jackson farm with a rotation of potatoes, oats, and clover 

 on Lane farm. In both rotations all the fertilizer was applied to the po- 

 tato crop. Yields of oat hay on Jackson farm follow fertilizer treatments, 

 the omission of an element causing a decrease, and the increase of an 

 element resulting in an increased yield. Liming affected oat yields favor- 

 ably. Hay yields were influenced very slightly by residual fertilizers but 

 more markedly influenced by liming. Data on oats and clover from Lane 

 farm are not included due to variable stands on different sections of the 

 field. 



Data on potato measurements show a tendency toward a shorter, 

 blockier potato for those grown under high potash, while high phosphorus 

 reverses this trend, a trend which is accentuated by omitting the potash 

 altogether. 



Lime on Potatoes 



On both Jackson and Lane farms the use of lime had very little effect 

 on potato yields. Fertilizers which left a strong residual acid reaction on 

 Jackson farm, however, failed to perform well in increasing or maintaining 

 yields, and the potato foliage exhibited symptoms typical of magnesium 

 hunger which would indicate that this soil is now or may soon be at the 

 critical point for soil acidity. 



Data from an experiment on L-eland farm, Greenland, show an in- 

 crease in potato yields on limed plots when the previous crop was utilized 

 as green manure. 



The influence of lime on potato scab is noted as well as the use of 

 acidulating substances to increase acidity and reduce scab effects. Of the 

 acidulating substances used, equal amounts of akuninum sulphate were 

 slightly more effective than sulphur in reducing scab and changing the soil 

 reaction. The use of these substances to change soil reaction and reduce 

 potato scab should scarcely be considered under farming conditions, but 

 it is felt that plowing under green manures or applying sulphate of am- 

 monia broadcast as a source of a part or all of the nitrogen in the potato 

 fertilizer would result in more economy to the potato grower as a remedy 

 for overliming. 



Organic Matter 



The three-year rotations practiced on both Jackson and Lane farms, 

 without organic manures, failed to maintain the organic matter level which 

 existed at the beginning of the trials. Jackson farm plots wdiich received 



