We cannot then call one piece of land more fertile than another until we know something about the skill and enterprise of its cultivators, and the amount of capital and labour at their disposal; and till we know whether the demand for produce is such as to make intensive cultivation profitable with the resources at their disposal.If it is, those lands will be the most fertile which give the highest average returns to a large expenditure of capital and labour; but if not, those will be the most fertile which give the best returns to the first few doses.The term fertility has no meaning except with reference to the special circumstances of a particular time and place.
But even when so limited there is some uncertainty as to the usage of the term.Sometimes attention is directed chiefly to the power which land has of giving adequate returns to intensive cultivation and so bearing a large total produce per acre; and sometimes to its power of yielding a large surplus produce or rent, even though its gross produce is not very large: thus in England now rich arable land is very fertile in the former sense, rich meadow in the latter.For many purposes it does not matter which of these senses of the term is understood: in the few cases in which it does matter, an interpretation clause must be supplied in the context.(11*)4.But further, the order of fertility of different soils is liable to be changed by changes in the methods of cultivation and in the relative values of different crops.Thus when at the end of last century Mr Coke showed how to grow wheat well on light soils by preparing the way with clover, they rose relatively to clay soils; and now though they are still sometimes called from old custom "poor", some of them have a higher value, and are really more fertile, than much of the land that used to be carefully cultivated while they were left in a state of nature.
Again, the increasing demand in central Europe for wood to be used as fuel and for building purposes, has raised the value of the pine-covered mountain slopes relatively to almost every other kind of land.But in England this rise has been prevented by the substitution of coal for wood as fuel, and of iron for wood as a material for ship-building, and lastly by England's special facilities for importing wood.Again, the cultivation of rice and jute often gives a very high value to lands that are too much covered with water to bear most other crops.And again, since the repeal of the Corn Laws the prices of meat and dairy produce have risen in England relatively to that of corn.Those arable soils that would grow rich forage crops in rotation with corn, rose relatively to the cold clay soils; and permanent pasture recovered part of that great fall in value relatively to arable land, which had resulted from the growth of population.(12*)Independently of any change in the suitability of the prevailing crops and methods of cultivation for special soils, there is a constant tendency towards equality in the value of different soils.In the absence of any special cause to the contrary, the growth of population and wealth will make the poorer soils gain on the richer.Land that was at one time entirely neglected is made by much labour to raise rich crops;its annual income of light and heat and air, is probably as good as those of richer soils: while its faults can be much lessened by labour.(13*)As there is no absolute standard for fertility, so there is none of good cultivation.The best cultivation in the richest parts of the Channel Islands, for instance, involves a lavish expenditure of capital and labour on each acre: for they are near good markets and have a monopoly of an equable and early climate.
If left to nature the land would not be very fertile, for though it has many virtues, it has two weak links (being deficient in phosphoric acid and potash).But, partly by the aid of the abundant seaweed on its shores, these links can be strengthened, and the chain thus becomes exceptionally strong.Intense, or as it is ordinarily called in England "good" cultivation, will thus raise ?00 worth of early potatoes from a single acre.But an equal expenditure per acre by the farmer in Western America would ruin him; relatively to his circumstances it would not be good, but bad cultivation.
