Scientific Research and Invention 137

industry, subject to the tyranny of the law of
“decreasing returns.” At a given stage of the science
 and art of agriculture, additional bushels of
wheat or of any other crop could be wrested from
the soil only with a disproportionately increased
expenditure of labor and capital. If there were no
changes in the methods of agriculture, foodstuffs
and other raw materials and products of the farm
must continuously advance in price as population
increases and the demand for farm products grows.
But this, which was the logic of Ricardo, Malthus
and their followers, implies that practices and appliances
 remain unchanged. Under such assumptions
the theory is correct. But economists cannot reckon
without taking account of the scientific researchers
and inventors who have revolutionized agriculture
half a dozen times since the eighteenth century,
until today scientific farming has been transformed
almost into a manufacturing industry.
Subsoil plowing, better fertilizers, better breeds
of farm animals, new and improved crops, utilization
 of waste products, and, last and most important,
improved means of transportation have increased
manifold the area and productivity of economic
land since Ricardo laid down his famous law of rent,
based upon the “permanent and indestructible qualities
 of the soil.”
Agricultural chemists long ago taught the farmer
the value of soil analysis for showing what lands
are suited to particular crops, what kinds of fertilizer
 to use. These chemists have found hundreds