Gardening When It Counts: Growing Food in Hard Times (Mother Earth News Wiser Living Series Book 5)

by Steve Solomon

the mineral nutrition of plants is more straightforward. Agronomists are confident about which minerals are required, and in what proportions. As an example, most plants use a lot of calcium, but for every six to eight measures of calcium, they’ll also need one measure of magnesium, maybe a sixteenth measure of sulfur, and one ten-thousandth measure of boron. If they have heaps of calcium but are short of magnesium, then they won’t be able to grow any more than the amount allowed by the quantity of magnesium they’ve got. If they have adequate calcium, magnesium, and sulfur, all in the right proportions for ideal growth, but are desperately short of boron, then they will grow as poorly as though they were short of calcium and magnesium and sulfur. Figure 2.1: Each stave in the barrel represents a different plant nutrient in soil. The ones at their full height are in full supply. The barrel at the left illustrates a soil in which the greatest deficiency is of nitrogen; plants will grow no better than the level of nitrogen. The barrel on the right shows that soil after nitrogen has been added. Now the most limiting deficient nutrient is potassium. The plants will grow no better than the level of potassium permits. According to Dr.William Albrecht, chairman of the soils department of the University of Missouri during the 1940s and 1950s, the broadest differences in soils are caused by climate. Albrecht repeatedly pointed out that where it rains just barely enough for agricultu...