MAKING LIMING PAY BETTER ought to have more attention now that we are using this soil treatment to feed calcium to plants rather than to fight soil acidity. This shift in purpose of liming points to possibilities in reducing the labor and financial load. Serving the single year needs of a crop for lime to make it better feed for livestock ought to be more encouraging than trying to remove completely a soil condition arising from many years of soil neglect.
Better feeding values in forages and healthier animals on soils treated with lime are recognized now that we have learned more about the services of calcium, or lime, to plants. In evaluating feeds as they supply proteins, carbohydrates, minerals, and vitamins one might not readily comprehend how calcium is connected with any of these items except, possibly, the minerals. But we know that calcium goes right along with nitrogen, the key item in protein. More nitrogen goes into plant protein only as more calcium is supplied by the soil. Then, too, phosphorus, which like nitrogen is also a part of the protein, is moved into the crop through addition of lime to the soil. This helps us to understand how calcium makes protein, even if it doesn’t come through as a chemical part of this nutrient complex. Lime in legumes is the force that moves phosphorus from the soil and nitrogen from the air, so the plant can run not only its protein and mineral factories, but also can be a better factory for possibly other complexes, such as vitamins, which make the big differences in the feed from limed soils when its full value is reflected in the animals that eat it.
We are so accustomed to thinking of legumes taking nitrogen from the air that we can scarcely imagine that they could fail in this process. Careful chemical studies show that unless they get lime liberally they don’t use air nitrogen. Can you imagine that soybeans could grow to be almost two feet high without taking nitrogen from the air? Would you believe that even some of the nitrogen and minerals in the seed were lost back to the soil by this crop? Under such soil conditions the resulting legume forage crop has less minerals and less protein in it than was in the seed at planting time. This has happened on soil too low in lime. Only when liberal lime allotment was offered by the soil and taken by the crop were the minerals from the soil and the nitrogen from the air moved into the crop to make it a real feed in place of so much woody packing for the poor animal’s paunch. Lime must get into the plant and serve there as a tool in fabricating the complex substances the plants make out of nitrogen, phosphorus and other plant nutrients.
Thus, legumes can be feeds, not merely because their pedigree labels them as such. Rather they are nutritious according as they have calcium within their plant tissue to help carry out their plant functions, and not necessarily because the lime application has corrected soil acidity. Feeding plants lime makes it possible for them to feed the animals with forage of nutritious value.
Young plants must get lime early in their life. This was demonstrated in studies by Dr. H. F. Rhoades, now at the University of Nebraska. When soybeans were started ten days in limed sand and transplanted to soil, they grew much more successfully than those transplanted from unlimed sand. Young plants without lime often die and look as if they had been hit by a fungus to make them “damp off.” Raising the delivery of calcium to the plant removed this “disease,” so when plants are “taken” by fungus disease it may not be so much the epidemic as it is a lack of vigor.
Have we been thinking enough of the health of the plant as it depends on our supplying its needs in soil fertility, of which calcium is the foremost item? Good feeding of the plants enables them to resist disease. Haven’t we possibly been throwing seed away, complaining about the failure of plants to fight off disease; haven’t we been purchasing disease-combating chemicals in place of recognizing this situation as indicating a fertility so low, first in lime, then in phosphorus and even other nutrients, that the soil delivery of those nutrients is too slow in the spring? In such cases the seed supply presumed to carry the plant into the warmer part of the growing season becomes exhausted before the soil delivery of nutrients is in higher gear. In place of taking up a fight against plant disease, perhaps we might well look to lime for help in “eliminating” weak plants by making them healthy and thus “immune” to disease because they are well fed.