60 INFLUENCE OF THE SEASON OF THE YEAR 



Now, these experiments are far from being conclusive : they 

 are only suggestive of further inquiry, by more extended and 

 more carefully conducted experiments on different soils, and in 

 varied seasons and circumstances. But they seem to indicate 

 that the presence of a comparatively small quantity of saline 

 matter of common salt or sulphate of soda, for example in 

 the surface-soil, may entirely overcome and mask the natural 

 effect of such substances as rape-dust when applied in certain 

 proportions. If such an influence of saline matter be possible 

 in any but very dry seasons, it must in many soils be constantly 

 exercised, and is deserving of the careful consideration of those 

 who concern themselves with the deductions which may be fairly 

 drawn from experimental investigations in the field. 



Rape-dust and saline substances are both favoured by moist 

 seasons. To the latter, moisture is necessary in a greater degree 

 than to the former ; and if such evils as the above can follow 

 from their common presence in the soil, we should expect them 

 only or mainly in very dry seasons. But the subject deserves 

 to be investigated by careful experiment ; and in a future chapter 

 I shall suggest such field-trials as appear to me likely to throw 

 light upon it. 



4. Influence of the time, manner , and form of its application 

 on the apparent efftct'of a manure ; also of the period at which 

 a root-crop is lifted. 



1. The time. There are various points connected with the 

 time of the application of a fertilising substance which are 

 deserving of consideration. Thus, 



a At what season of the year it should be applied. It has been 

 found by experiment, that in the same season, and on the same 

 field, gypsum applied as a top-dressing to young clover produced 

 less effect when it was laid on in March than when it was spread 

 in April.* But the subject of the most economical period for 

 the application of different substances to different soils and crops 

 has not as yet been made a subject of careful experiment. 



The only series of experiments with which I am acquainted, 



* See my little book On the use of Lime in Agriculture, p. 207. 



