**3. The conflict between Oyaizu and Daikuhara on biochar fertilizer: ca. 1890–1912**

The conflict between Oyaizu and the scientists began in about 1890. A year after Oyaizu published a leaflet on methods to produce fertilizer by heating soil [22], Dr. Oskar Kellner, a German agricultural chemist who had been invited to teach agricultural chemistry at the Komaba School of Agriculture (the predecessor of Faculty of Agriculture at the University of Tokyo) reported that production of such fertilizer was worthless [23]. His comments were based on an analysis by Dr. Max Fesca, a German agronomist who also taught agronomy at the Komaba School of Agriculture.

From the 1900s to the 1930s, the ammonium sulfate market in Japan shifted from importation to domestic production. In 1902, sales of commercial fertilizers was largest for soybean meal (28% of the total amount), which was followed by fish meal of herring and sardine (27%), chemical fertilizers (14%) and rapeseed oil cake (13%) [19]. Chemical fertilizers included superphosphate, ammonium sulfate and sodium nitrate, but the percentage of their sales to

In the 1910s, the Haber-Bosch process of ammonia synthesis was invented in Germany. The rapid German commercialization of the Haber-Bosch process, however, was not followed by a similarly rapid conquest of the world fertilizer market [20]. In 1913, Chile, possessing huge deposits of sodium nitrate, was the largest producer of nitrogen in the world (56.5%) and Germany was the second (15.6%) [21]. At that time, Japan accounted for only 0.5% of world production. As shown in **Figure 2**, production increased rapidly thereafter. By 1934, Japan accounted for 10.5% of world production and had become the third largest producer in the

**Figure 2.** Annual production of ammonium sulfate and superphosphate in Japan during the Taisho (1912–1926), Showa (1926–1989) and Heisei (1989–present) periods. The values were derived from data in several fertilizer hand‐

**3. The conflict between Oyaizu and Daikuhara on biochar fertilizer: ca.**

The conflict between Oyaizu and the scientists began in about 1890. A year after Oyaizu published a leaflet on methods to produce fertilizer by heating soil [22], Dr. Oskar Kellner, a German agricultural chemist who had been invited to teach agricultural chemistry at the Komaba School of Agriculture (the predecessor of Faculty of Agriculture at the University of Tokyo) reported that production of such fertilizer was worthless [23]. His comments were

the total amount was slightly more than 10%.

206 Organic Fertilizers - From Basic Concepts to Applied Outcomes

world after Germany (23.5%) and the United States (13.0%).

books published by the Association of Agriculture and Forestry Statistics, Tokyo.

**1890–1912**

The article appeared in 1887 began by noting that heated soil fertilizer had already been reported as having a number of merits in *Nogyo Moukun* (agricultural textbook) published by Shosaku Itoh in 1840. Kellner said, "Someone appeared recently who engages in the production and extension of heated soil fertilizer, but the outcome is not always satisfactory". By "some‐ one" Kellner clearly meant Oyaizu, although his name was not used. Kellner pointed out that, in order to evaluate the benefits of heated soil fertilizer, it is necessary to examine the effect of heating treatments on the content of fertilizer elements in the soil. Analytical results were provided by Fesca. A soil sample was treated with heat followed by addition of an ammonia solution. The soil samples (untreated soil, heated soil and heated soil treated with an ammonia solution) were subjected to extraction with about 10 mol L–1 hydrochloric acid, and the concentration of fertilizer elements in the extracts was determined. The concentration of nitrogen in the heated soil was less than half of that in the original soil. Volatilization of ammonia during the heating and watering treatments was indicated. The concentrations of phosphorus and potassium were not different among the samples. It was concluded from these results that the use of heated soil fertilizer was neither effective nor economical.

Years later, Oyaizu recalled this event [2] and wrote, "Mr. Fesca, a German specialist employed by the Ministry of Agriculture and Commerce, reported that heated soil fertilizer is of no value. My business suffered a setback."

Some of the Japanese agronomists who were taught by Kellner and Fesca also criticized the leaflet written by Oyaizu [3]. It is likely that Daikuhara was also influenced by these German teachers. From 1897 to 1990, Daikuhara carried out an extensive survey on heated soil fertilizer at the Kinai Branch of the Imperial Agricultural Experiment Station in Osaka Prefecture [7].

In a report entitled "Studies on heated soil fertilizer" [24] and published in 1901, Daikuhara wrote, "The effects of heated soil fertilizer have been experienced by local farmers and recorded in old books." He reported that heated soil fertilizer was still being produced in 10 of Japan's 47 prefectures and that it was frequently used in Hyogo, Hiroshima, Oita and Tottori Prefec‐ tures. Unlike some of his colleagues, however, Daikuhara did not completely agree with the conclusions of Kellner and Fesca. He wrote, "Mr. Fesca used strong hydrochloric acid for extracting soil samples. This method is not suitable to evaluate the content of soil nutrients available to crops. I agree with his comment on the loss of nitrogen by volatilization. For the other elements, however, the content of plant-available fraction must have been influenced by the heating treatments. This could be revealed by extracting samples with dilute acid solutions instead of strong hydrochloric acid."

Daikuhara prepared heated soil samples by heating soil in a pan for 20 minutes. For the analyses, he used 1% solution of hydrochloric acid, oxalic acid and citric acid as well as strong hydrochloric acid solution. He also conducted plant growth experiments several times (**Figure 3**) and obtained new findings. Most importantly, he found that the contents of nitrogen, phosphorus and potassium extracted by dilute acid solutions were increased in the heated samples, whereas the whole contents of nitrogen and organic matter were decreased. In this way, he determined the fraction of soil nutrients available to plants and succeeded in obtaining soil analytical results which agreed with crop growth better than before.

**Figure 3.** Barley grown with heated soil fertilizer and/or chemical fertilizer (N, P and K) in Daikuhara's first prelimina‐ ry experiment [24]. The photo and the data are cited from a collection of his papers [11]. The photo was taken in the middle of April 1898 at the Kinai Branch of the Imperial Agricultural Experiment Station, Osaka Prefecture. The four treatments in the picture are heated soil without chemical fertilizer (H), heated soil with chemical fertilizer (HC), origi‐ nal soil without chemical fertilizer (O) and original soil with chemical fertilizer (OC). This preliminary experiment was carried out in the open system using an earthen pipe as a pot and a sandy soil as a growth medium. The growth and yield of barley in the OC treatment were better than those of the O treatment, indicating that the growth was limited by fertilizer elements. Furthermore, the growth and yield in the H and HC treatments were better than those of the OC treatment. If we assume that the growth of barley was limited by nitrogen, then the inhibition of nitrification by soil heating (for example, see [25]) and the prevention of downward leaching of very mobile nitrate in a sandy soil may be responsible for the better growth in the H and HC treatments in addition to the enhanced mineralization of soil organ‐ ic nitrogen by heating [26].

Daikuhara was the first Japanese scientist to use a dilute acid solution to extract nutrients from soil. According to his study [27], he had been impressed by pioneering work by Dr. Bernard S. Dyer published in 1894 [28]. Dyer was an agricultural chemist in the United Kingdom who proposed the use of a solution of 1% citric acid to determine whether a soil is in need of phosphate fertilizer. Dyer wrote in his paper, "It may be said to have been pretty widely recognized that some very much weaker solvent than strong mineral acid ought to be used in soil analyses, if these are to be of much use as indications of the proportion of available mineral plant food."

Although the overall results indicated that heated soil fertilizer can be valuable, at the end of the report, Daikuhara added the following supplementary note: "The heated soil fertilizer analyzed in this report is different from the so-called new fertilizer composed of a mixture of charred straw and human waste. Currently, someone is encouraging the use of this fertilizer. But its value is not worth describing at all." Again, this "someone" was Oyaizu, and the "new fertilizer" referred to biochar fertilizer.

way, he determined the fraction of soil nutrients available to plants and succeeded in obtaining

**Figure 3.** Barley grown with heated soil fertilizer and/or chemical fertilizer (N, P and K) in Daikuhara's first prelimina‐ ry experiment [24]. The photo and the data are cited from a collection of his papers [11]. The photo was taken in the middle of April 1898 at the Kinai Branch of the Imperial Agricultural Experiment Station, Osaka Prefecture. The four treatments in the picture are heated soil without chemical fertilizer (H), heated soil with chemical fertilizer (HC), origi‐ nal soil without chemical fertilizer (O) and original soil with chemical fertilizer (OC). This preliminary experiment was carried out in the open system using an earthen pipe as a pot and a sandy soil as a growth medium. The growth and yield of barley in the OC treatment were better than those of the O treatment, indicating that the growth was limited by fertilizer elements. Furthermore, the growth and yield in the H and HC treatments were better than those of the OC treatment. If we assume that the growth of barley was limited by nitrogen, then the inhibition of nitrification by soil heating (for example, see [25]) and the prevention of downward leaching of very mobile nitrate in a sandy soil may be responsible for the better growth in the H and HC treatments in addition to the enhanced mineralization of soil organ‐

Daikuhara was the first Japanese scientist to use a dilute acid solution to extract nutrients from soil. According to his study [27], he had been impressed by pioneering work by Dr. Bernard S. Dyer published in 1894 [28]. Dyer was an agricultural chemist in the United Kingdom who proposed the use of a solution of 1% citric acid to determine whether a soil is in need of phosphate fertilizer. Dyer wrote in his paper, "It may be said to have been pretty widely recognized that some very much weaker solvent than strong mineral acid ought to be used in soil analyses, if these are to be of much use as indications of the proportion of available mineral

Although the overall results indicated that heated soil fertilizer can be valuable, at the end of the report, Daikuhara added the following supplementary note: "The heated soil fertilizer analyzed in this report is different from the so-called new fertilizer composed of a mixture of charred straw and human waste. Currently, someone is encouraging the use of this fertilizer.

ic nitrogen by heating [26].

plant food."

soil analytical results which agreed with crop growth better than before.

208 Organic Fertilizers - From Basic Concepts to Applied Outcomes

What was the difference between heated soil fertilizer and biochar fertilizer? Both fertilizers are prepared by smoldering organic matter. In the case of heated soil fertilizer prepared in the fields, plant residues such as tree branches, mulberry branches and rice husks are covered with soil, and a mound of soil is prepared. After setting fire to plant residues in the mound, the surrounding soil is treated with heat for several days (**Figure 4**). The product thus prepared is a mixture of heated soil, ash and charred materials. The heated soil fertilizer that Oyaizu recommended in the leaflet [22] was produced in a similar way but in a kiln. The main ingredient was rice stubble and soil together with rice straw as a fuel. After smoldering these materials, other ingredients (sulfur, human waste, salt and fish meal) were added to harmonize the composition of fertilizer.

**Figure 4.** A mound of soil smoldered for the production of heated soil fertilizer. The picture is reprinted from a leaflet of an Okuno-type apparatus to prepare heated soil, which was produced and sold by Marukome Shokai. The date of photograph is unknown, but it is probably from about 1935. Although buried and unseen in the picture, this apparatus made of iron was the most popular type before the Pacific War (1941–1945). The production of the apparatus was re‐ stricted severely by the shortage of iron during the war [29].

To prepare biochar fertilizer, Oyaizu recommended preparing a hole with a depth of about 1.4 m and a diameter of 1.8 m [2]. A bundle of rice straw is then set on fire and thrown into the bottom of the hole. Subsequently, additional plant residues of any kind are thrown into the hole several times until white smoke emerges without a flame. After a few hours of smoldering, diluted human waste is poured onto the charred materials. The last step can be omitted when green grasses are used as an ingredient.

Because heated soil fertilizer contains heavy soil and biochar fertilizer does not, these materials are expected to be different in terms of the weight per unit volume. However, what Daikuhara wanted to say in the above note was not such a scientific matter but his opinion that biochar fertilizer cannot become as valuable as heated soil fertilizer.

Oyaizu was angry at the reaction by scientists, and wrote [2], "In 1900, I submitted the outcomes from experiments to the Ministry of Agriculture and Commerce, so that biochar fertilizer would be produced widely. As a result of the analysis by the authorities concerned, however, the biochar fertilizer was regarded as valueless in the same way as the heated soil fertilizer I proposed before. The authorities and scientists rejected all of my results. This event disappointed me very much." The Imperial Agricultural Experiment Station was the "author‐ ities concerned" to which Daikuhara belonged at that time.

In such circumstances, Oyaizu was supported by Mr. Masayoshi Inoue, a bachelor of agricul‐ ture who had made efforts to support the use of biochar fertilizer. Inoue wrote [30], "So-called agronomists did not pay any attention to biochar fertilizer on the grounds that it contained little nitrogen, phosphorus and potassium." Inoue also referred to Daikuhara's report on heated soil fertilizer and complained, "On heated soil fertilizer, a certain doctor at the Imperial Agricultural Experiment Station in Tokyo published a report. But he focused on the effect of soil heating only. Charred materials present in the heated soil fertilizer were not described at all." The "certain doctor" is Daikuhara. He had moved from Osaka to Tokyo in 1903 [7]. As noted above, he prepared a heated soil sample in a manner different from local farmers, and there was no biochar in his samples.

Why did Oyaizu believe in biochar fertilizer, despite the criticism from the agronomists? This is probably because he had conducted field trials by himself and with many farmers and found empirically that the application of biochar fertilizer improved crop productivity (**Figure 5**). In his book [2], he wrote, "In order to support the growth of living crops, it is necessary to apply a living body to them." and "Biochar fertilizer is a living body which provides the following functions; 1) absorption and preservation of heat, 2) absorption of moisture, 3) absorption of nitrogen, 4) effects on sterilization, and 5) effects on soil quality." According to the traditional classification of fertilizers by Nobuhiro Sato in the Edo period, "a living body" is a type of fertilizers originating from living creatures (mainly animals) such as human waste, horse dung and fish meal. Although Oyaizu had written that he was impressed by the thoughts of Sato and the biochar fertilizer he proposed did contain human waste, it is not clear whether Oyaizu followed the traditional definition precisely. The term "a living body" was omitted by his son, when the book was revised and enlarged in 1915 [31]. We can at least safely say that Oyaizu considered that the effect of biochar fertilizer was not limited to the contents of fertilizer elements, but it extended to its capacity to absorb heat, water and nitrogen.

hole several times until white smoke emerges without a flame. After a few hours of smoldering, diluted human waste is poured onto the charred materials. The last step can be omitted when

Because heated soil fertilizer contains heavy soil and biochar fertilizer does not, these materials are expected to be different in terms of the weight per unit volume. However, what Daikuhara wanted to say in the above note was not such a scientific matter but his opinion that biochar

Oyaizu was angry at the reaction by scientists, and wrote [2], "In 1900, I submitted the outcomes from experiments to the Ministry of Agriculture and Commerce, so that biochar fertilizer would be produced widely. As a result of the analysis by the authorities concerned, however, the biochar fertilizer was regarded as valueless in the same way as the heated soil fertilizer I proposed before. The authorities and scientists rejected all of my results. This event disappointed me very much." The Imperial Agricultural Experiment Station was the "author‐

In such circumstances, Oyaizu was supported by Mr. Masayoshi Inoue, a bachelor of agricul‐ ture who had made efforts to support the use of biochar fertilizer. Inoue wrote [30], "So-called agronomists did not pay any attention to biochar fertilizer on the grounds that it contained little nitrogen, phosphorus and potassium." Inoue also referred to Daikuhara's report on heated soil fertilizer and complained, "On heated soil fertilizer, a certain doctor at the Imperial Agricultural Experiment Station in Tokyo published a report. But he focused on the effect of soil heating only. Charred materials present in the heated soil fertilizer were not described at all." The "certain doctor" is Daikuhara. He had moved from Osaka to Tokyo in 1903 [7]. As noted above, he prepared a heated soil sample in a manner different from local farmers, and

Why did Oyaizu believe in biochar fertilizer, despite the criticism from the agronomists? This is probably because he had conducted field trials by himself and with many farmers and found empirically that the application of biochar fertilizer improved crop productivity (**Figure 5**). In his book [2], he wrote, "In order to support the growth of living crops, it is necessary to apply a living body to them." and "Biochar fertilizer is a living body which provides the following functions; 1) absorption and preservation of heat, 2) absorption of moisture, 3) absorption of nitrogen, 4) effects on sterilization, and 5) effects on soil quality." According to the traditional classification of fertilizers by Nobuhiro Sato in the Edo period, "a living body" is a type of fertilizers originating from living creatures (mainly animals) such as human waste, horse dung and fish meal. Although Oyaizu had written that he was impressed by the thoughts of Sato and the biochar fertilizer he proposed did contain human waste, it is not clear whether Oyaizu followed the traditional definition precisely. The term "a living body" was omitted by his son, when the book was revised and enlarged in 1915 [31]. We can at least safely say that Oyaizu considered that the effect of biochar fertilizer was not limited to the contents of fertilizer

elements, but it extended to its capacity to absorb heat, water and nitrogen.

green grasses are used as an ingredient.

210 Organic Fertilizers - From Basic Concepts to Applied Outcomes

there was no biochar in his samples.

fertilizer cannot become as valuable as heated soil fertilizer.

ities concerned" to which Daikuhara belonged at that time.

**Figure 5.** *Mugi* (probably barley) grown at the Imperial Agricultural Experiment Station (Nishigahara, Tokyo) in 1912, with an aid of a political party "*Dai-Nippon Koudou Kai*" to Oyaizu. *Mugi* is a general Japanese term including wheat and barley. The picture is reprinted from the book revised by Oyaizu's son [31]. Plants on the right were grown with the application of biochar fertilizer, whereas plants on the left were grown by the conventional method. The Oyaizu group and the Experiment Station began collaborating on the cultivation of *mugi* with biochar fertilizer in 1910, but few quantitative results were reported by the station [2].

In the first chapter of his book [2], Oyaizu expressed his viewpoint as follows, "It is evident that Western science, however progressive it is, is not a universal truth. I cannot understand why so-called scientists in our country are eager to copy it. Originality is most important, because we, Japanese, have traditional knowledge of agriculture." A year after the book was published, Oyaizu passed away. Following the wishes he expressed, the coffin was filled with biochar fertilizer [3].

It should be noted that we have interpreted Oyaizu's words as we understand them. His intended meaning might have been different from our interpretation. Although we had trouble in understanding parts of it, his book starts with the theory of Yin and Yang, the Chinese philosophy that has influenced the development of science in Asia, including Japan (the socalled Eastern science) (**Figure 6**). Harmonization of fertilizer according to the Yin and Yang theory was regarded as critically important in *Nogyo Zensho* by Miyazaki; for example, *yakigoe* (burned fertilizer) should be used in combination with *mizu-goe*(liquid fertilizer containing human waste) for the harmonization of Yin and Yang in order to support the growth and ripening of crops by the power of Yin and Yang, respectively [32]. Therefore, it is not an exaggeration to say that the conflict between Oyaizu and Daikuhara was representative of the larger struggle between the two established philosophies, one from the East and the other from the West.

**Figure 6.** A circular crop calendar proposed by Oyaizu and printed in 1917 after his death (left). In the circle, summer and winter are depicted in red and blue colors, respectively, and the seasons rotate clockwise. Field management is described in the inner peripheral part. This calendar is designed to inform farmers on the suitable seasons for each field management practice in the double cropping of rice and *mugi*. It is a part of the schematic diagram called "Har‐ monization of Yin and Yang" with the length and width of 105 cm and 39 cm, respectively (right). The contents of the calendar are also explained in Oyaizu [31].
