54 



On the average, the seven plots dressed with sulphate of 

 ammonia produced about a ton per acre more roots than 

 the nitrate plots ; and the rape dust plots were about equal 

 to the latter. Looking at the results of the individual 

 plots, we see that in only two cases out of the seven did 

 nitrate give a higher yield than sulphate. Of these one 

 was the plot receiving superphosphate, which confirms 

 what we have already noticed ; and the other was the basic 

 slag plot, where possibly some of the nitrogen of the 

 sulphate of ammonia may have been lost through the 

 action of the lime of the slag. The high produce of 

 sulphate of ammonia with dissolved bones, compared with 

 nitrate is worth noticing ; for the results of many experi- 

 ments seem to show that the use of dissolved bones with 

 sulphate of ammonia gives particularly good returns. 



In ordinary farm practice, the use of sulphate of am- 

 monia adds very much to the weight of the crop, and to 

 the extent of about i cwt. per acre may be relied on to 

 repay its cost and leave a profit. As we have seen with 

 other crops, potash manuring seems peculiarly helpful to 

 its action. The sulphate should be applied at the. time of 

 sowing, and will generally be found to give particularly 

 good results in seasons in which growth goes on late in the 

 year. It has been noted by many experimenters that 

 turnips grown with sulphate of ammonia are more healthy, 

 and keep better, than those grown with nitrate. This is 

 to be expected from what we have already said as to the 

 effect of the manures on the rankness of growth of all crops. 



POTATOES. 



The Rothamsted experiments naturally claim first atten- 

 tion with this, as with the other crops we have dealt with. 

 For the first twelve years of experiment in the continuous 

 growth of potatoes on the same land, the following were 

 the average weights of potatoes of different qualities per 

 acre per annum, and the percentage of diseased tubers 

 produced by various manurings.* 



TABLE XXXIII. 



* "Agricultural Students Gazette," New Scries, IV., 2. 



