The Importance of Foliar Application
There is a major reason why I can so strongly emphasize the necessity of foliar application: I have conducted actual experiments using radioisotopes to compare the behavior of various fertilizer elements absorbed through roots and through leaves. People sometimes ask, “What are radioisotopes?”—this is something you learn in high school chemistry and physics, so I encourage readers to look it up. After the war, research using radioisotopes finally began at Japanese universities. The most advanced work at that time was being carried out in the laboratory of Professor Zenzaburo Kasai at Kyoto University. I voluntarily applied to join this laboratory, passed the entrance examination for the master’s program, and was admitted. Even many Kyoto University students failed this examination (this is a fact), but I decided to take the exam during the latter half of my sophomore year at Hyogo Prefectural College of Agriculture in Tamba-Sasayama (now the Faculty of Agriculture, Kobe University), studied intensively, and eventually passed. This was a laboratory with a long tradition, and at that time, Professor Yasuyuki Yamada—who later received the Order of Culture in 2012 (Heisei 24) and is now Professor Emeritus at Kyoto University and the Nara Institute of Science and Technology—was still young and was conducting experiments on foliar mineral absorption using radioisotopes in Professor Kasai’s laboratory.
At the Hyogo Prefectural Agricultural Experiment Station, I served as the chief supervisor for the handling of unsealed radioisotopes. This required passing a national examination, and the laboratory was subject to on-site inspections once a year, while maintenance costs were also substantial. In fact, after my retirement, since there were no longer any researchers using radioisotopes, the laboratory was quickly shut down, and today there are no radioisotope laboratories remaining in Hyogo Prefecture.
At that time, the radioisotope laboratory belonged to the biotechnology research division, which was very popular at that time. The institute was newly established and initially had a relatively generous budget, which made my research life there particularly favorable. That biotechnology institute has since been abolished. As an aside, the former Chemistry Division, where I later became department head, was subsequently merged with plant pathology and entomology laboratories to form a large Environmental Division. Although the Chemistry Division had been the core of this group, today only three staff members and a laboratory remain. After my retirement, the name “Chemistry Division” disappeared from the organizational structure, and the crucial three-element fertilization trials have now been suspended.
Development of a Rapid Nutrient Testing Method
This project is the work for which I received the highest praise from my superiors during my career as a staff member of the Hyogo Prefectural Agriculture, Forestry and Fisheries Technology Center. Specifically, when I was promoted from Researcher Grade 2 to Grade 1, my supervisor, the late Mr. Shoji Kusaka, then Director of the Chemistry Division, went to the Personnel Division carrying a single set of reagents, analytical samples (plant tissues and soil), test tubes, and a small amount of distilled water. He reportedly said with a laugh, “If I demonstrate how easily fertilizer elements in plants and soils can be analyzed like this and explain that Mr. Kazuhiko Watanabe has developed research that benefits agriculture in Hyogo Prefecture, that will be more than enough to pass.”
Of course, even though it has now been twenty years since my retirement, younger staff members continue to manage the reagents, and this method is still explained every year in training sessions for agricultural extension officers. Although the information can also be found online, it is described in detail in the “Guidelines for Reducing Chemical Fertilizer Use,” published by the Hyogo Prefectural Department of Agriculture, Forestry and Fisheries in February 2023 (Reiwa 5): specifically, on page 15, “4. Determination of Appropriate Fertilizer Application Rates Based on Soil Diagnosis, (3) u. Measurement Using the Rapid Nutrient Testing Method,” and on page 21, “(3) e. Diagnostic Criteria for Measurement Results.” In addition to these written guidelines, hands-on training workshops are reportedly held once a year. The analytical reagents are prepared by researchers in charge of soil and fertilizer studies, and they are distributed to those who bring empty containers to the laboratory.
About ten years ago, in the laboratory of Professor Chikahiro Miyake, Department of Applied Functional Biology, Plant Nutrition, Graduate School and Faculty of Agriculture, Kobe University, students were also instructed to prepare rapid nutrient testing reagents and perform various measurements. I was once invited to give a lecture explaining the rapid nutrient testing method to the students, and Professor Miyake himself was surprised by its simplicity. Farmers in Hyogo Prefecture can visit their local agricultural extension centers, where extension officers will analyze samples on the spot. Because nitrogen, phosphate, potassium, and other nutrients can be measured so easily, I believe farmers in Hyogo are truly fortunate.
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
