J. H. Gilbert— Points in connection with Vegetation. 27 



In the case of wheat and barley it was seen that a mixed 

 mineral manure increased the yield of nitrogen to a verv small 

 degree only. Not so in the case of the leguminous crop! 1 .cans. 

 During the first twelve years a complex mineral manure, <'<>n- 

 taining a large amount of potass — 1 call attention to this fact 

 because we have abundant evidence that it is the potass chielly 

 that is effective — uave I) bo lbs. of nitrogen p. r acre per annum 

 against 4S 1 lbs. obtained over the same period without manure. 

 During the next twelve years, the potass manure uavc 2!>vi lbs. 

 against scarcely half as 'much, or 14-6 lbs. without the potass 

 manure. And finally, during the whole period of twenty-lour 

 years, the potass manure has given 45 - 5 lbs. of nitrogen per 

 acre, per annum, against 81 3 lbs., or only about two thirds as 

 much, without manure; and we have more than twice as much 

 yielded by a potass manure over a period of twenty four rears 

 with bean's than with either wheat or barley. 



Before calling attention to the figures relating to another 

 leguminous crop — red clover— it should be mentioned that 

 leguminous crops generally are. and clover in particular is, 

 extremely sensitive to adverse climatal circumstances; but 

 clover is pre eminently sensitive to soil conditions also. Indeed, 

 it is a fact well recognized in agriculture, that few soils can be 

 relied upon to grow a good crop of clover oftener than once in 

 about eight years; and many soils will not yield it so fre- 

 quently. It will not excite surprise, therefore, that in attempt- 

 ing to grow clover year after year on the same land, we have 

 only succeeded in getting any crops, and some of those poor 

 ones, in six years over a period of twenty- two. Indeed, the 



spring succeeding the sowing of the seed ; when, in some cases 

 a crop of wheat or barley was taken, and in others the land was 

 left fallow. Hence, over a period of twenty-two years we have 

 had only six years of clover, one of wheat, three of barley, 

 and twelve of "fallow. Still, the annual yield of nitrogen over 

 the twenty-two years was 305 lbs. without any manure, and 



• 

 tural point of view, still it is seen that the influence of the inter- 

 polation of this leguminous crop bssg I the yield 

 of nitrogen comparer 1 in either wheat or 

 barley grown continuously; and that, unlike the result with 

 those crops, a potass manure has here again, as with beans, 



Without attempting for the moment to discuss the probable 

 source or sources of this wreath eased vi 1 , litrogen by 



leguminous as cornpaifd with n rain in w i - I ill sini| \ 

 here remark in passing that we have no evidence leading to the 



