EXPEEIME^'TS OX POTATOES WITH DIEFEEEXT MAXUEES. 285 



too light, and though very even for the Oolitic* formations, there 

 is considerable variety in the same half-acre of land. It was 

 therefore determined to try every dressing as above stated in 

 triplicate, the different plots of each triplicate being carefully 

 distributed so as to counterbalance irregularities. The size of 

 the plots were Y12 ^^ ^^ acre, or 51'8 yards' run of one potato 

 drill. This plan of small plots in triplicate has been repeatedly 

 found to give the most accurate results, far more so than when 

 large plots of half an acre are tried singly. 



On April 21st the furrows on the whole piece having been 

 split open with the double mould board plough, the various 

 dressings were applied as on the main crop, with great care 

 down the central portion of the furrow. The sets were then 

 carefully planted so as to ensure perfect regularity, and at once 

 covered in. 



As the crop grew it was observable that those plots to which 

 the 2 cwts. of sulphate of ammonia had been applied looked the 

 most vigorous ; but as they ripened these same plots showed 

 most disease on the shaws. It may be mentioned that a crop of 

 Eegent potatoes which had been planted on the side of the pre- 

 vailing and dampest wind were very much diseased, and it is 

 probable that the accelerated ^spread of the disease amongst the 

 Champions was due to this, as they turned out more diseased 

 than was anticipated. The latter part of June and July was 

 remarkably wet, as also was September, and the disease mani- 

 fested itself in the Eegents at the end of July, so that the 

 disease was throughout all the potato crops over an average. 



The potatoes were dug and weighed on 18th October, and the 

 weights on each plot are seen in Table I., which also shows the 

 distribution of the plots and the weights of the manures per 

 acre. Table II. column 1, contains the average result of each 

 manuring obtained by adding together the weights of the three 

 triplicates, and then dividing the sum by three. This result is 

 stated in column 1, and it will be seen that the whole of the 

 bone superphosphate results are averaged, also those of the whole 

 of the coprolite superphosphates, and those of the whole of the 

 ground coprolites ; and from this it is seen that the yield from 

 bone superphosphates exceeds that from coprolite superphos- 

 phates by 13 cwts., and that from ground coprolite by 1 ton 

 18 cwts. It must be remembered that in each of these quantities, 

 •each tried in triplicate, the total quantity of nitrogen applied is 

 equal ; therefore, it is evident that the soluble phosphates pro- 

 duce the greatest crop, and of the two kinds the bone superphos- 

 phates surpasses the coprolite superphosphates when in conjunc- 

 tion with sulphate of annnonia. 



* The Oolitic formation is ii vnricty of limostono, consisting of minute 

 spherical grains. 



