288 



THE YEAR-BOOK OF AGRICULTURE. 



way ; seed planted whole. Hoed twice ; last time slightly hilled. We have made selections 

 from the principal results, and embodied them in the following table, which shows the pro- 

 duce of the three varieties without any manure, and the effect of the various fertilizers applied 

 in the hill at the time of planting. 



There is a striking difference in the yield of the three varieties the Mercer, in every case, 

 producing less than the Irish lunkers and the Carters. They have, however, as a general 

 thing, fewer unsound potatoes. The Carters appear to be exceedingly liable to disease. In 

 one instance, No. 4, with compost, more than half, or eighty-three and a half bushels out of 

 one hundred and fifty-two and a half, were unsound. 



The hog-manure in the second, as in the first experiments, gives the greatest increase with 

 each variety. The Carters, with this manure, gave two hundred and eighty-two bushels in 

 the aggregate, or two hundred and sixty bushels of sound potatoes, per acre. In these days 

 of potato degeneracy, this is a good crop. Long, unfermented manure gives a compara- 

 tively poor crop with all the varieties. Poudrette, wheat-bran, hen-manure, and ashes have 

 but a slight beneficial effect. Lime gave no increase, and gypsum would seem to have done 

 more harm than good, since, with the Irish lunkers, the plot receiving a tablespoonful of 

 plaster in the hill actually yields ten and a half bushels per acre less than that with no ma- 

 nure. This confirms the common opinion that plaster has little or no effect on low, moist soil ; 

 while on dry upland it usually proves beneficial. In the first year's experiments, on 

 " gravelly loam," plaster applied when the potatoes were up gave an increase of twenty-six 

 bushels per acre, and, applied in the hill at the time of planting, an increase of thirty-two 

 bushels per acre. 



The comparative value of superphosphate of lime and guano for potatoes is a matter of 

 discussion just now, and we were in hopes that these experiments would have thrown some 

 light on the subject. Unfortunately, however, the guano was applied in the hill with the 

 potato, and, of course, the " seed was injured" and the crop lessened. Under these circum- 

 stances, it is hardly surprising that the guano, except in one instance, gives a less in- 

 crease than the superphosphate. Our own experiments and observations on this point lead 

 us to the conclusion that good Peruvian guano is a far superior manure for potatoes than 

 superphosphate of lime. And, indeed, Mr. E. found, in another experiment with Irish 

 lunkers, that guano, applied on the top of the hill at the time of planting, produces a better 

 crop than superphosphate of lime similarly applied. Thus the unmanured plot gave per 

 acre seventy-eight and a half bushels ; the superphosphate, one hundred and ten and two- 

 thirds bushels ; and the guano, one hundred and fifty-six bushels. It is said, too, that in this 

 case also the seed was injured, though doubtless less so than where the guano was in actual 

 contact with the tubers. It is seen that the guano doubles the crop, and gives forty-five 

 bushels per acre more than the superphosphate of lime. A tablespoonful of saltpetre (ni- 

 trate of potash) applied in the hill gave seventy-five and two-thirds bushels per acre, or three 

 bushels less than where nothing was applied. This is in accordance with the previous year's 



