Now We Know Lime is a Plant Food—Not Merely a Treatment for Acidity
FOR BOUNTIFUL PRODUCTION in agriculture we must always work with, not against, the stern laws of nature. Sciences are doing much to help in our understanding of nature’s ways in the growth of our crops, our livestock and ourselves. But this knowledge still is not complete enough to keep us free from occasional but significant errors.
Such errors most often come about when we try to move too quickly with programs designed to change the habits and thinking of large groups. If we allow time for individuals of the groups to learn and understand basic principles, such errors are not too likely to occur. Then, the new behavior will be the result of changes by each individual—not just because he joined the group. Campaigns dealing with farm production changes may suffer from lack of sufficient understanding at the outset of basic natural forces.
The campaign for liming the soil based on the slogan, “Fight soil acidity” is an illustration. We have added to our understanding of how the soil serves to nourish the plant via its roots. Thus, we ought to be rethinking the wisdom of the idea of fighting soil acidity to the point of getting rid of it—of making the soil “neutral.”
Serious disturbances, even disasters, in crop production, followed by irregularities in animal feeds on those crops grown on “neutralized” soils, indicate fighting soil acidity with carbonate of lime in limestone is not in accordance with natural facts of plant creation.
The cry, “Lime the soil for legumes,” was well received by the public, followed by such slogans as “Grow legumes to build up the soil.” Both of these farm slogans now are being reconsidered for the serious errors delaying activities for better food production. Soil exploitation rather than soil restoration was increased.
While legumes have the ability to fix nitrogen (they can take nitrogen from the free supply in the air as well as the limited supply in the soil) we find they do not necessarily carry out this philanthropic service to the soil. They are not always using atmospheric nitrogen merely because they are growing.
There have been no measurements of nitrogen fixation by legumes growing in the field that are accurate enough to tell us just how much nitrogen is taken from the air by a legume crop. Also, even if a legume takes nitrogen from the air to make plant growth, that nitrogen is made a part of the plant tissue, more in the tops than in the roots. This nitrogen is not made a part of the soil to any extent unless the entire crop is sacrificed on the spot and plowed under. We are now learning that acidity of the soil is not to be blamed when legumes fail to grow on those soils that have become highly acid from the forces of nature. Soils where the rainfall is high, particularly where virgin forests once grew but have been cleared, fail to grow these protein-producing, nitrogen-fixing legumes because these crops do not find enough fertility.
The missing soil nutrients were lost because acidity, or hydrogen, came in to replace them. Decaying or “souring” forest litter made much acid for that effect. The growing trees were setting free acidity or hydrogen from their leaching rainfall. These soils were growing only wood when the pioneers took them over. Shall we expect legumes planted there to make much more than woody tissue even if they grow there? Plants grow because they can put acid out of their roots thru respiration. Plant growth is possible because plants trade that acidity to the soil and take fertility in exchange. If there is acidity present along with plenty of fertility in the soil, then plants grow better than if that fertility is not accompanied by any acidity.
We now are coming to see that had we known more about how plants feed with their roots in the soil, there would have been no “war” on soil acidity. Instead, each of us would have undertaken our separate responsibilities to rebuild our soil first with calcium supplied with limestone. That work might well have started 25 years earlier. Perhaps we would have lime to supply magnesium, too. Had we looked upon increasing soil acidity as nothing more than decreasing soil fertility, we could have believed our soils are declining in supplies of all nutrients, including the trace minerals now so disturbing as to their possible needs.
Only as our understanding of the natural behaviors and natural laws of nature increases, will we farm more effectively on the soil that provides the creative potential for farming. For creation of farm products we need to supply the soil with the fertility for which plants trade their acidity.