EXPERIMENT STATION BULLETINS. 



223 



to be but little diff ereuce betAveen the rows with coverings of 1 and 2 inches, 

 the corrected total yield l)eing slightly larger for the 2 inch, and the cor- 

 rected marketable yield for the 1 inch" covering. Where the coverings are 

 3, 4 and 5 inches the yield is considerably less. 



AVith an open well drained soil we have obtained best results by planting 

 in trenches 5 inches deep and covering 2 inches. The trenches can be 

 gradually filled when cultivating, after the plants are up, or better yet by 

 dragging the field across the rows with a smoothing harrow as soon as the 

 sprouts appear. This will level the land and destroy all weeds. A second 

 harrowing and frequent working with a Planet Jr. or other cultivator, with 

 level cultui-e, will give satisfactory results. 



Total Yield. 



Planted different depths. 



Covered 1 inch. 



Covered 2 inches. 



Covered 3 inches. 



Covered 4 inches. . 



Covered 5 inches- 



440 

 47S.2 



432 



540 



380 

 500 



Marketable. 



- 3 



No. of I Weight of No. of ' Weight i>f No. of I Weight of = 



Tubers. Tubers. Tubers. Tubers. Tubers. Tubers. o 



Unmarketable. 



54.5 I 86 lbs. 5 oz. 



5.92.3 I 93 



13 



410 76 lbs. 9 oz. 

 512.5 95 " ii " 



362 

 393.4 



78 lbs. 183 



84 •' 13 oz. 198.9 



236 1 65 lbs. 1 oz.l 174 



295 I 81 •■ 5 " I 217.5 



79 lbs. 12 oz. 280 66 lbs. 8 oz 

 86 " 11 " 304.4 \ 72 ■• 4 " 



73 lbs. 8oz. 244 

 91 " 14 " ' 305 



60 lbs. 



78 " 14 OZ. 



262 

 344.7 



59 lbs. 13 oz. 



74 ■■ 12 " 



51 lbs. 10 oz. 

 67 '• 14 '• 



160 



173.8 



188 

 235 



118 

 155.3 



8 lbs. 5 oz.l 46 



9 " 1 '• \ 50 



11 lbs. 8 oz. 

 14 " 6 " 



13 lbs. 4 oz. 



14 " 7 " 



13 lbs. 11 oz. 

 17 " 2 " 



40 

 50 



46 

 50 



40 

 50 



8 lbs. 6 oz. 38 

 11 "■ \ 50 



POTATO SCAB. 



It is now generally admitted that the scabs and cracks on potatoes are 

 caused by some injury, mechanical or otherwise, to the tuber. They first 

 appear at the so-called lenticels, which are .small pimples on the surface of 

 the potatoes and serve as breathing spots. If the cells at this point are 

 injured, an attempt is made to repair the injury, and layers of corky cells 

 are formed which jDroduce the so-called scab. These spots often spread, 

 and running together form large blotches. The cause of the injury to the 

 lenticels has not been ascertained. It has frequently been attributed to 

 insects and fungi. Wire worms are sometimes found feeding on scabby 

 potatoes, and although we have no evidence that they attack perfect tubers, 

 they may do so, and in that case, scab would undoubtedly be produced. 

 Scab, however, is very prevalent in fields where wire worms cannot be 

 found, and it must there be attributed to some other cause. It is not 

 believed that fungi are in any way the cause of scab, although they are 

 sometimes found on potatoes where scab has already developed. 



Among the other causes that have been mentioned are, continued 

 drought, excessive moisture, or a drought followed by heavy rains, and the 

 presence of various corrosive substances in the soil, as lime, iron, or 

 ammonia. From our present knowledge of the scab, any of these or more 



