i9o6.] Manuring of Crops in Rotations. 



91 



fruits or carpels of Slierardia arvensis (field madder), one side 

 of which is rounded and the other flat and furrowed, some of 

 the seeds being covered with short white hairs, while the three 

 sharp hard points of the calyx leaves at the top are well defined. 

 The seeds of Geranmin dissectiim (cut-leaved geranium), are 

 also found, and are known by their oval shape, greyish-brown 

 colour, and pitted or net-marked surface. The purity of trefoil 

 at a fair price is, as a rule, high, and there is not any difficulty 

 in obtaining seeds having a purity of 98 per cent. or. 99 per cent. 

 The germination of seed of average price can also be depended 

 upon to equal 94 per cent, or 95 per cent. 



D. FiNLAYSON. 



The residual value of manures or the extent to which their 

 effects are felt in years subsequent to their application is a 

 subject of great agricultural interest, but 

 Manuring' of ^j^^ g^^^ ^^^^ ^^^^ of g^^^ difficulty, as 

 Crops in ' 

 Rotations. order to eliminate as far as possible 



separate factors, such as peculiarities of soil 

 and variations of climate, the experiments require to be con- 

 tinued for a series of years. This has been the case in a set of 

 rotation experiments which form the subject of an exhaustive ' 

 report by Professor Gilchrist, of Armstrong College, Newcastle- 

 on-Tyne. Here six separate centres were available, in two of 

 which the trials have extended over twelve years (three rota- 

 tions), and over ten years (two rotations) at two others, the 

 remainder representing one rotation each of four or five years. 

 The experiments are of too extensive a character to be sum- 

 marized here, but the general conclusions at which Professor 

 Gilchrist arrives can be understood without reference to the 

 experiments in detail. 



It is evident, for instance, that if soil is allowed to run down 

 in condition it takes a long time to bring it again into "good 

 heart." This is shown by the steady increases in the gains 

 during the twelve-year experiment. These increases are largely 

 the result of comparison with the unmanured plot, which has 

 been undergoing a gradual exhaustion. 



In the majority of cases the manures applied for swedes have 



