166 



Professor G. V. Poore 



[April 24, 



BAI?LEy 



PROOOCC PER ACRE 



IH" 



While it is impossible to over-estimate the debt which agriculture 

 owes to chemistry, we have, nevertheless, learnt from the bacterio- 

 logist that there are biological problems underlying the question of 

 fertility, and that a mere chemical estimation of the constituents of 

 organic manure is insufficient, by itself, to fix its manurial value. 

 It is by the agency of bacteria that organic matter is changed into 

 nitrates and other soluble salts, which are absorbed by the roots of 

 plants and serve to nourish them. This change only takes place 

 provided the temperature and moisture are suitable and the ground 

 be properly tilled. Drought and frost arrest the change, and excess 

 of moisture, by closing the pores of the soil, does the same thing. 



Organic manures are economical in the long run, because if the 

 weather is adverse they bide their time until the advent of " fine, 

 growing weather." If one season prove unfavourable a large amount 

 of the organic matter remains in the soil to nourish the next crop. 

 This is not the case when soluble chemical manures are used. 



That it is necessary to put dung uj)on the ground if we are to 

 maintain the fertility of the soil, has been the experience of all 

 peoples in every age. 



I will now display a diagram which represents by a curve the 



yearly produce of barley in bushels 

 per acre, grown continuously on the 

 same jDlots of ground for forty years, 

 but with this difierence, that one plot 

 (represented by the upper curve) 

 received 14 tons per annum per acre 

 of farmyard manure, while the other, 

 represented by the lower curve, has 

 been unmanured continuously (Fig. 1). 

 This diagram has been constructed 

 from figures given by Sir John Lawes 

 and Sir Henry Gilbert in the ' Trans- 

 actions of the Highland and Agricul- 

 tural Society of Scotland' for 1895. 

 I have replaced fractions by the 

 nearest whole figure. The fluctua- 

 tions of both these curves are very 

 great, and it will be noticed that 

 they are exactly parallel to each 

 other. This teaches us that weather 

 is the most important factor in agri- 

 cultural success, and shows the ex- 

 treme danger to the farmer of "placing 

 all his eggs in one basket," as has 

 been done by the so-called farmers of 

 the far West, who have attempted to grow wheat only by the process 

 of scratching the prairie without returning any dung to the soil, and 

 many of whom have been financially swamped by the first bad season. 



Fig. I. 



