EXPERIME^^TS ON POTATOES WITH DIFFEKEXT MANURES. 297 



12), 29-31 per cent. ; (plots 3, 8, 13), 28*63 per cent. ; and (plots 

 33, 38, 43), 29-37 per cent. All of them are above plot 24 

 (unmanurecl), 28*03 per cent., and plot A, 28*5 per cent. It is 

 clear, then, that the addition of any soluble manure has been 

 productive of good effects, when considering only the solid 

 matter. Fittbogen (who introduced the manure into the soil 

 three weeks before placing his " sets ") found that the " super " 

 lowered the dry matter, and that kainit, with or without super- 

 phosphate, produced tubers containing the smallest amount of 

 dry matter. Eeference to any of the plots (except 28, 12, 13), and 

 comparison with 24 and A and B, will show that our results are 

 very different ; but I find that ammonia and superphosphate alone 

 have given better results than when kainit has been added. 

 The effect of potashes has been good when considering the 

 average amount, but the maximum amount is considerably below 

 the maximum of the other plots. 



Sttmmary. '—V>OTiQ superphosphate has produced in all cases the 

 most valuable tuber, whether the phosphate was used alone 

 (which was the most satisfactory) or when mixed with ammonia 

 or potash, or with both, the starch being generally in the largest 

 quantity, and the water in least. The addition of ammonia 

 slightly detracts from the percentage of starch, and adds a little 

 to the water ; but, on the other hand, the nitrogenous matter is 

 distinctly increased, — however, in a form of no value as regards 

 feeding. (See Table V.) 



Insoluble phosj^hate does not appear to advantage as regards 

 .starch, with but one exception (43), and it seems generally to 

 have increased the albuminous matter, and to have decreased the 

 ash and the fibre when in conjunction with other manures ; but 

 seeing that these two last are very subordinate constituents of a 

 potato, its use could not be especially recommended in further 

 trials. That bone superphosphate should have produced the best 

 results is somewhat remarkable, as like quantities of nitrogen 

 were present -in both superphosphate applications ; and in the 

 case of the " mineral superphosphate " it was in a mure advanced 

 stage for assimilation by the plants, and according to Marcker 

 (Bied. Centr., 1880, 409) ammonia, to produce its effects, must 

 first be converted into nitric acid ; hence it was to be expected 

 that the nitrogen in the Ijone superphosi)hate would act more 

 slowly and produce its effects more tardily than the nitrogen in 

 the added sulphate of ammonia. Whether the sulphuric acid 

 present has had a retarding inthience is a matter yet to be deter- 

 mined.* 



* Althouf^h Plot B has been frequently quoted in tliis report, it nnist be dis- 

 tinctly understood that no <(reat importance can bo attached to the results 

 obtained, as no special care was taken in its [>ri'i)aration, it bciuf? (juite an after- 

 thought, was made at a later date, and was not intendcil to have been introduced 

 into this report. Tlie analyses of its protbiee nrp, however, of value. 



