CHAPTER 29

Limestone Mobilizes Other Fertility Too—It’s The Soil That Feeds Us

PUTTING LIME ON THE SOILS of the humid region has been practiced under the belief that removal of the acidity of the soil was the benefit from such a treatment. We now know that liming an acid soil is helpful because of the nutritional value of the calcium and magnesium supplied to the crops, by it, and because it helps to mobilize other nutrient elements into the early plant’s growth.

Experiments, with a crop like soybeans, demonstrated the need by the young seedlings for calcium early in their life if they were to survive. Any forms of calcium salts showed their benefits. These benefits were the same regardless of whether these salts reduced the soil acidity or whether they increased it. If the soybean seedlings were planted in a lime-bearing sand for no longer time than 10 days and were taken up, washed, and transplanted into a soil, the plants were taller, grew better and gathered more nitrogen from both the soil and the air ever after, than when the first 10 days of their growth were in a lime-free sand. Additional trials with other seeds have demonstrated the earlier emergence and better stands of the crop when the seeds were coated with lime or when this plant nutrient was dusted into the soil along with the planting of the seeds. All of these demonstrations indicate that the calcium of the lime is beneficial by the entrance of the calcium early into the seedling stage of plant growth.

More refined experiments were required to demonstrate the fact that lime as calcium, not as carbonate, serves to mobilize or move other nutrients into the crop. Korean lespedeza, originally imported and claimed to be an “acid-soil crop,” showed very clearly its higher concentrations of nutrients other than calcium, when the soil was given this element in the soil treatment of liming. By growing test plants in a colloidal clay-sand mixture, it was shown that calcium was required to a relatively high degree of saturation on the clay if the plants were to grow. As this degree of saturation was increased, or as the amount of clay with any degree of calcium saturation put into the sand was larger—to give the plants more calcium—there was more potassium, more nitrogen, and more phosphorus taken into the plants. Lime was the leader, apparently, of the nutrients and was bringing them into the plants.

Here was ample reason for one to become “lawyer for the defense” of the unsuspecting cow that would be asked to consume a soybean “hay crop” grown on a lime-deficient soil. This would be the case on soils for which the early propagandists for this imported legume said “This is a hay crop if not able to be a seed crop.” Fed on hay from this crop grown on such soils, the cow would gain less nitrogen, and less phosphorus, for example, on eating the hay crop than if she had eaten the seed that was originally planted. That a plant may be growing and making vegetative bulk while it is losing nitrogen, or potassium from the planted seed back to the soil may still be doubted. But when some of our animals demonstrate their health disasters on much that is called “feed” because it is “plant growth,” we ought to suspect that some thing like nutrients going in the reverse directions might be taking place.