MANURES. 221 



(oxygen) in the soil is necessary for the growth of 

 crops, and especially so during the earlier stages. Not 

 only is air necessary for the plants themselves but also 

 for the numerous chemical and bacteriological changes 

 which are continually taking place. In fact one of the 

 evil effects of stagnant water in the soil arises from the 

 exclusion of air, which results in changes injurious to the 

 health of the plant. Thus, we may conclude that while 

 manuring and fertility are closely connected, yet the latter 

 depends on conditions other than the presence of an abund- 

 ant supply of plant food. In fact it is quite possible to 

 conceive a soil amply provided with all the necessary 

 ingredients for plant life in a suitable form, and yet to be 

 quite unproductive. It is clear therefore, that what is 

 generally called the physical properties of the soil have a 

 most important bearing on fertility, and that the presence 

 of plant food alone should not be our only consideration. 

 This is a point on which it is well to dwell, for many 

 cultivators in attaching, and rightly, so much importance 

 to the question of manure supply have shown a tendency 

 to err in the direction of supposing that large applications 

 of manures are all that are necessary for the raising of 

 maximum, crops. This is not only erroneous, but we may, 

 on the other hand, state that the expenditure of large 

 sums for manure, necessitates a more careful observance 

 of the rules of successful husbandry in order that the 

 fullest advantage may be obtained from the investment. 

 There are many features to which attention could with 

 advantage be drawn, such as the importance of the pro- 

 duction of a suitable tilth, but these matters will receive 



