MANURES 105 



soil, but of a temporary character only; and, since much of the 

 material accumulated in the leaves is derived from the lower 

 depths, it will enrich the surface soil, providing an easily available 

 supply of mineral food (as well as of organic matter) for further 

 growth. 



There is, where the ground is tilled, another circumstance which 

 operates in the same way; this is the growth of weeds. In a 

 soil like that at Ridgmont, where six or seven hoeings of the 

 ground during the season are necessary to keep it clean, the 

 amount of food-material which is thereby brought to the surface 

 will be considerable, and such ground may be considered as 

 being continually under green manurial treatment, with the 

 beneficial results attendant thereon. 



As to the practical conclusions which are to be drawn from 

 these results : since it is certain that the absence of any effect 

 of manures on fruit trees at Ridgmont is not due to any excep- 

 tional fertility of the soil, it is evident that similar results must 

 be expected elsewhere under like conditions, and that, in such 

 cases, all money spent in manuring the land would be thrown 

 away, just as it has been at Ridgmont. But before interpreting 

 this as a general conclusion that manuring is unnecessary, we 

 must carefully consider what the conditions at Ridgmont really 

 were. In the first place, the soil is heavy and fairly fertile, and 

 not deficient in any one of the elements essential to plant-growth ; 

 where the soil is poor, either in one or all food constituents, and 

 especially where it is light, and where such nourishment as it 

 contains is easily washed down beyond the reach of the roots, 

 manuring is essential, as was clearly shown by the results at 

 Millbrook. In the second place, the crops at Ridgmont were 

 light, owing to circumstances independent of the soil ; thus 

 the records refer to the first 22 years of the life of the planta- 

 tion, not to 22 years of its existence after it had attained full 

 maturity, whilst the natural cropping of the trees was much 

 reduced by the destructive action of spring frosts. Under other 

 circumstances, the average cropping might have been three or 

 four times as great as it was, and probably in such a case the 

 soil could not have borne the drain on its resources without the 

 addition of manure. Observations made at Harpenden, however, 

 seem to point to the contrary, and it must be remembered 

 that the drain caused by increased cropping is always dis- 

 counted to a certain extent by diminished growth, and that 

 there is, consequently, not so much difference as might at first 



