**1. Introduction**

"Biochar" is a recently coined term used to denote a carbon-rich product obtained when biomass, such as wood, manure or leaves, is heated with little or no available air. It is similar to the term "biosolid," which is used to describe treated sewage sludge for agricultural use. The term biochar only applies to the material used as a soil amendment and is distinguished from charcoal used for fuel or as a reductant [1].

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In Japan, material containing biochar has long been used as a fertilizer to improve soil quality and to increase crop production. For example, it is described as *yaki-goe* (burned fertilizer) in *Nogyo Zensho* (an encyclopedia of agriculture), which is one of the earliest agricultural textbooks called *nosho* and was written by Yasusada Miyazaki and published in 1697 during the Edo period (1603–1868). After reading the book *Nibai Shukaku Tenri Nouhou (How to Double Crop Yield by Almighty Farming System)* published in 1912 [2], we also found that there were conflicting opinions between the author and scientists who doubted the benefits of the use of biochar as a fertilizer.

Mr. Katsugoro Oyaizu, an agricultural extension worker, wrote the book and strongly advocated the use of *kuntan hiryo* (biochar fertilizer) for various crops [3]. Oyaizu was born in 1847 in Aichi Prefecture. In about 1880, he began to conduct agricultural experiments and promoted the use of heated soil as a fertilizer. From 1887 to 1888, he served as an agricultural extension worker in Aichi Prefecture. Based on his knowledge of heated soil fertilizer, he proposed a method to produce biochar fertilizer to the government in 1900 and summarized it in his book, which became a bestseller.

Dr. Gintaro Daikuhara was one of the scientists who disagreed with Oyaizu on the effects of biochar fertilizer. Daikuhara was born in 1868 in Nagano Prefecture, and thus was about 20 years younger than Oyaizu. A year after graduating from the College of Agriculture, Tokyo Imperial University (the predecessor of the University of Tokyo) in 1894, he joined the staff of

**Figure 1.** Photographs of Katsugoro Oyaizu (left) and Gintaro Daikuhara (right). The photo of Oyaizu is reprinted from his book [2], and the photo of Daikuhara is reprinted from a collection of his papers [11]. The dates of photo‐ graphs are not known. Reproduced from our study [12] with permission from the Japanese Society of Soil Science and Plant Nutrition.

the Imperial Agricultural Experiment Station where he served as an agricultural chemist for 27 years [4]. His publications on soil acidity [5] and a new method of its determination [6] attracted worldwide attention [7]. He also wrote textbooks on soil science in Japanese [8, 9], which contributed to establishing the basis of modern soil science in Japan [10].

In Japan, material containing biochar has long been used as a fertilizer to improve soil quality and to increase crop production. For example, it is described as *yaki-goe* (burned fertilizer) in *Nogyo Zensho* (an encyclopedia of agriculture), which is one of the earliest agricultural textbooks called *nosho* and was written by Yasusada Miyazaki and published in 1697 during the Edo period (1603–1868). After reading the book *Nibai Shukaku Tenri Nouhou (How to Double Crop Yield by Almighty Farming System)* published in 1912 [2], we also found that there were conflicting opinions between the author and scientists who doubted the benefits of the use of

Mr. Katsugoro Oyaizu, an agricultural extension worker, wrote the book and strongly advocated the use of *kuntan hiryo* (biochar fertilizer) for various crops [3]. Oyaizu was born in 1847 in Aichi Prefecture. In about 1880, he began to conduct agricultural experiments and promoted the use of heated soil as a fertilizer. From 1887 to 1888, he served as an agricultural extension worker in Aichi Prefecture. Based on his knowledge of heated soil fertilizer, he proposed a method to produce biochar fertilizer to the government in 1900 and summarized

Dr. Gintaro Daikuhara was one of the scientists who disagreed with Oyaizu on the effects of biochar fertilizer. Daikuhara was born in 1868 in Nagano Prefecture, and thus was about 20 years younger than Oyaizu. A year after graduating from the College of Agriculture, Tokyo Imperial University (the predecessor of the University of Tokyo) in 1894, he joined the staff of

**Figure 1.** Photographs of Katsugoro Oyaizu (left) and Gintaro Daikuhara (right). The photo of Oyaizu is reprinted from his book [2], and the photo of Daikuhara is reprinted from a collection of his papers [11]. The dates of photo‐ graphs are not known. Reproduced from our study [12] with permission from the Japanese Society of Soil Science and

biochar as a fertilizer.

Plant Nutrition.

it in his book, which became a bestseller.

204 Organic Fertilizers - From Basic Concepts to Applied Outcomes

**Figure 1** shows the photographs of Oyaizu and Daikuhara. Both of them studied the effects of biochar fertilizer, but reached different conclusions. This episode has been written by several researchers, mainly by historical sociologists (for example, see [3, 12–14]). But these reports are available in Japanese only, and they are often written from a sociological viewpoint with limited insight to the experimental data.

In this chapter, we introduce these two agronomists and their thoughts on the use of biochar fertilizer with a parallel focus on the growth of modern soil science and fertilizer market in Japan. By referring to the publications of Oyaizu and Daikuhara et al, we attempt to unveil the conflict between traditional knowledge of biochar fertilizer and new concepts of soil science that had been imported from the Western countries in the early twentieth century. We also describe briefly the socioeconomic impacts on the use of biochar fertilizer in the later genera‐ tions.
