284 EXPEFJMENTS OX POTATOES AVITH DIFFEEENT MA^'URES. 



namely, the Champion — so as to avoid as much as possible com- 

 plications which would arise whea a portion of the crop was lost 

 through disease, and thus enable the effect of ammoniacal 

 manure on the increase of the crop to be tried undisturbed as 

 far as possible, as, with non-disease-resisting varieties, it is 

 well known that ammoniacal dressings increase the tendency to 

 disease. 



Three sources of phosphoric acid have been employed so as to 

 test in which it is most available for the potato. Thus, so-called 

 bone superphosphate — made to all appearance half with boues 

 and half with ground coprolite — was tried against coprolite 

 superphosphates and also against ground coprolites, each in 

 such quantity that the dressing contained between 88 lbs. and 

 89 lbs. of phosphoric acid per acre. As there was a small 

 quantity of undecomposed nitrogenous compounds in the bone 

 superphosphates, an equal quantity of nitrogen in the form of 

 sulphate of ammonia (35 lbs. per acre) was added, so that the 

 bone superphosphate should have no advantage on account of 

 its nitrogen over the other two. This constitutes the first series, 

 which may be called for convenience the " unaided phosphates," 

 though there can be no doubt that even this small quantity of 

 nitrogen has had a material effect. 



The second series consists of Xo. 1 series, plus an addition at 

 the rate of 2 cwts. per acre of sulphate of ammonia to each of 

 the three. 



The third series consists of No. 2 series, plus 2 cwts. of kainit. 



The fourth series consists of No. 2, plus 56 lbs. of potashes 

 substituted in place of the kainit. 



Thus, it will be observed, the three phosphates are tested 

 against one another under four varying conditions — alone ; in 

 conjunction with sulphate of ammonia; in conjunction with sul- 

 phate of ammonia, plus kainit; and in conjunction with sulphate 

 of ammonia, plus potashes. 



The effect of sulpihate of ammonia is tested by comparing the 

 results of the three unaided phosphates with the same plus sul- 

 phate of ammonia. The effect of kainit is tested three times 

 over by comparing members of the second series with the corre- 

 sponding members of the third series. That of potashes by com- 

 paring members of the fourth series with members of the second 

 series ; and by comparing the fourth with the third series the 

 two forms of potash are compared with one another three 

 separate times. Besides this, each manurial application is tried 

 in triplicate, so that the phosphates are tested against one 

 another twelve times, and the sulphate of ammonia nine times, 

 kainit nine times, potashes nine times. 



The field chosen is perhaps the best potato soil of any on the 

 farm. The experimental piece is slightly too heavy rather tlian 



