92 
Artificial Manures for Swedes. 
widely from each other in composition, and consequently 
possessinfi^ totally different specific actions on vegetable life, are 
tried against each other ; or powerful fertilisers occasionally are 
employed in quantities, or in a mode in which they injure instead 
of benefiting the plants ; and a variety of other mistakes not 
seldom are committed, and other circumstances of importance 
overlooked, which all tend to affect the result of the trial. Thus 
for instance, experiments with different fertilisers occasionally are 
tried on land which is in so excellent a condition that the best 
manure hardly makes any impression on the yield of the crop. 
It is forgotten that the agricultural capabilities of soils cannot be 
increased ad libitum to any extent, and that consequently the 
addition of the most valuable fertiliser to land which has almost 
reached its maximum state of fertility, which it either possesses 
naturally, or into which it has been brought by long cultivation, 
will produce no more effect than the most worthless manuring 
mixture. Land in such a high state of fertility can be compared 
to the replenished stomach of a well fattened animal ; the one is 
as little benefited by the best manure, as the other is by the 
choicest food. On the contrary, the most powerful fertilisers 
applied under such conditions are exactly those which may and do 
occasionally even produce undesirable effects on vegetation, just 
as the richest food is more apt to spoil a satiated stomach than a 
plainer dish. 
Hence it is that statements to the effect that such or such a 
manure has produced as great an effect as the best Peruvian guano, 
or any other manure of well-known fertilising power, or lias even 
surpassed the best manures in its effects, find their way into the 
hands of dealers in trashy manures, or to say the best of the 
manures of a very inferior description. For this reason the 
printed testimonials which accompany the offer for sale of 
artificial manures do not always possess that value which many 
attach to them, not even when they are the genuine emanations 
of well-known and strictly honest agriculturists ; for as I have 
said already, trustworthy inferences from the results of experi- 
mental trials can only be drawn, if a vast variety of circumstances 
are taken into account, the recognition of which requires much 
experience, and I am almost inclined to believe, a special training 
for this branch of experimental inquiry. Comparatively speaking, 
lew men accustomed to practical pursuits during the greater part 
of their life, and dependent for the support of their families upon 
their business, are in a position to execute and direct field ex- 
periments with sufficient accuracy for the results to confer any 
permanent benefit on the farming community. It is indeed an 
unjust accusation which is sometimes made against the practical 
