Mechanism of Humic Acid and Fulvic Acid
When compost is applied, crop roots tend to grow more vigorously. Because we agricultural researchers routinely observe actual root development in crops, we can state with confidence that “the primary effect of compost is to promote root growth.” However, until recently, I had no understanding at all of the mechanism by which roots elongate.
I have several colleagues in the research community. One of the most notable is Mr. Noboru Uesugi, former president of Zen-Pi Shoren: the Japan Fertilizer Dealers Association. Mr. Uesugi has been serving as an advisor to the company of Mr. Yasushi Kojima, whom he introduced to me several years ago, and together they have reportedly collected around 400 research papers on humic and fulvic acids.
At last, Mr. Uesugi provided me with a paper that clearly explained the mechanism by which humic and fulvic acids promote root elongation. We immediately discussed this paper at our monthly English academic paper reading group held by my nonprofit organization, the Institute for Food and Agricultural Health, together with Ms. Satoko Nishino and others who have assisted us with translations. This paper is introduced in Section 11 of this chapter. Around the same time, we also decided to hold a study session on humic substances at my home together with Mr. Uesugi’s study group.
Humic acid binds with auxin inside the root, activates ATPase in the cell membrane, and converts ATP into ADP, releasing protons (H⁺) into the cell wall and thereby acidifying it. This activates low-pH-sensitive enzymes, promoting cell wall loosening and root elongation growth. By also utilizing the electrical gradient, the uptake of various nutrients increases, further enhancing root growth.
Most importantly, because ATP is decomposed and inorganic phosphate (Pi) is released, it became clear that even in the plots without phosphorus application of the three-element fertilizer trials mentioned earlier, compost-treated plots are not in a state of complete phosphorus deficiency. Solving this difficult question was refreshing, and I believe readers will feel the same sense of clarity. Compost releases inorganic phosphate within the roots!
Effects of Sulfur and Salt
In this chapter, I would like to explain the roles of sulfur (S) and chlorine (Cl), which are essential elements, yet whose functions are not well known to many people. From my own experience, at the time when the chemistry division of the agricultural experiment station began to focus seriously on sulfur-related pollution issues, a new researcher, Ms. Fumiyuki Asakawa, was assigned to this topic. At that time, she was investigating the damage caused by sulfur dioxide gas resulting from the smoke pollution in Yokkaichi. Since I was in charge of radioisotope research, she asked for my cooperation in studying what happens when sulfur dioxide gas comes into contact with crops.
We immediately exposed potted tomato plants to sulfur dioxide gas labeled with the radioisotope ³⁵S inside a vinyl-sealed chamber. The autoradiogram on the left of Photo 1 (page 160) shows that the sulfur from the sulfur dioxide gas accumulated mainly at the tips of the leaves. The image on the right shows the distribution of ³⁵S in the plant seven days later, clearly indicating translocation toward the basal parts of the plant. This demonstrated that tomatoes absorb sulfur from sulfur dioxide gas through their leaves and translocate and utilize it as a nutrient.
Later, at the 1994 meeting of the Japanese Society of Soil Science and Plant Nutrition, Professor Jiro Sekiya of Kyoto University gave a lecture stating, “In Europe, bread that does not rise properly has become a problem. In recent years, bread wheat contains less methionine due to sulfur deficiency caused by reduced air pollution, resulting in bread that fails to rise sufficiently.” I had been completely unaware of this, and it left a strong impression on me. Even hydrogen sulfide from air pollution had played a beneficial role. Of course, after that, the problem was solved by applying sulfur-containing fertilizers.
Next, let us consider chlorine. I was invited by Mr. Hiroshi Kinoshita of Hyponex Japan Co., Ltd. to join him at the annual “OFA Short Course,” held at Ohio State University for floriculture growers. As he mentioned that the program included lectures on soil and fertilizer science, I accompanied him there on two occasions. The lectures were designed for flower growers and were easy to understand, and they were very informative for me as well. What surprised me most was that flower growers were being advised to apply salt as a means of pest and disease control, because “salt is effective in controlling many plant diseases and pests” (see Table 2 on page 166).
Related Posts to New Common Knowledge About Nutrients
Health Benefits of Nitrate Ions／Correcting Zinc Deficiency
Boron Is Essential for Both Plants and Animals / Silicic Acid Is a Valuable Substance
