Furthermore, luxuriant foliage protects the soil from erosion better than does sparse foliage. Water is consumed more or less per area, and higher yields distill away little more water and leave little more residue of salt than do low yields. Seed is planted per plot, and choosing a higher yielding variety has no effect on the surroundings. If the improved variety resists pests, farmers who had controlled pests with chemicals will apply less, and farmers who had suffered depredations will lose less. On the other hand, high yields require more of certain activities than do low ones.
Fertilizer exemplifies factors that farmers use abundantly to raise yields.
I assume that less fertilizer to produce a given yield means less fallout of fertilizer into the environment or surroundings of a field. Although the price of fertilizer and the return on it have guided past decisions, ways of adding sufficient fertilizer for abundant yields with less fallout into the environment have long been known. In 1895, G. Liebscher, and in 1924, E. A. Mitscherlich offered amendments to Liebig's law. All three hypotheses concern a factor that limits yield and can be increased to raise yield. All state that eventually a maximum yield set by other factors places a ceiling on the increases that the limiting factor can cause.