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<\/small><\/p>\nFigure 1. <\/span>National soil map and distribution as a proportion of area (%)<\/span><\/strong>In the Japan Soil Inventory, one can view a soil map covering the whole of Japan, which was drawn up using the latest soil classification system (Comprehensive Soil Classification System of Japan: First Approximation). One can see that Andosols, which account for 31% of Japan’s total land area, are commonly located in the southern Hokkaido, northern Tohoku, Kanto, and Kyushu regions.<\/p>\n<\/div>\n The soil map that formed its basis was compiled via a survey program launched by the Ministry of Agriculture and Forestry (now the Ministry of Agriculture, Forestry and Fisheries) in the 1950s. Over a period of almost 20 years, from 1959 to 1978, the ministry conducted the Fundamental Soil Survey for Soil Fertility Conservation, with the aim of efficiently ensuring soil productivity and conserving soil fertility. Surveyors dug holes to a depth of 1 m every 500 m on agricultural land across the country and identified the properties of the soil. The survey data was then compiled and incorporated into maps. However, there were few opportunities for farmers to actually view the completed paper maps. They were not usually made available to the public, and producers could only get to see them if they went to the trouble of inquiring with the prefectural agriculture promotion agencies, so the reality was that farmers had no idea what kind of soil their land had. In addition, as the distribution of agricultural land has changed significantly since the survey was conducted, agricultural land is now also located in areas that were not surveyed at the time. Accordingly, the current database was produced after updating the data to include around 400,000 locations that were not surveyed at the time, on the basis of expert knowledge.<\/p>\n As can be surmised from the fact that the initiative was originally launched by the Ministry of Agriculture and Forestry, soil is a resource from which food production originates. For each type of soil, there are crops suited to its properties. The six main factors of soil formation are climate, vegetation, topography, parent rock (the rock from which the soil originates), time, and human activity. We can contribute to agriculture by conducting research to ascertain how these factors operate and thereby shed light on soil properties. I have heard that many of the users of the Japan Soil Inventory are agricultural promotion agencies, Japan Agricultural Co-operatives, and producers. There are actually cases in which, even when a crop is cultivated in the same way in neighboring fields, one field will yield a plentiful harvest, while the other yields nothing at all. This is because the soils are completely different, despite the fields’ proximity. There is tremendous significance in the fact that it has become easy to access the information needed to check soil conditions.<\/p>\n The soils shown in blue on the Japan Soil Inventory soil map indicate Lowland soils (Figure 2). As can be gathered from the fact that they are mainly distributed around rivers, the principal parent material of Lowland soils includes sediment deposited by river flooding. Lowland soils are classified into five subgroups and are generally known to be fertile soils, because the repeated addition of sediment from river floods keeps the parent material in a fresh state at all times, and they are also generally rich in nutrients. One can see that such soils are common in the major rice-producing areas of Niigata Prefecture, Akita Prefecture, and Yamagata Prefecture. Although the total area of Japan accounted for by Lowland soils is only around 14%, they account for about 70% of land used for paddy fields in Japan. This is because they are the optimal soils for rice cultivation—which requires the soil to be covered with water—as Lowland soils tend to be clay-rich and poorly drained, due to their high water table.<\/p>\n Figure 2. <\/span>Lowland soil (Collected in Takamatsu City, Kagawa Prefecture)<\/span><\/strong>Lowland soils are classified into five groups, one of which is Gray Lowland soils. There is a layer of iron mottling (soil with a reddish-brown mottled appearance resulting from the buildup of iron due to fluctuations in the water table) within 50 cm of the surface.<\/p>\n<\/div>\n The ability of a soil to nurture agricultural crops is called soil fertility, and this depends on how good or bad the soil is at retaining water and retaining nutrients (i.e. drainage, permeability, and nutrient retention capacity). The appropriate crops to produce differ according to the properties of the soil. For example, the reason why attempts to cultivate soybeans on land suited to paddy fields fail is that soybeans dislike water. If a farmer wishes to stop growing rice and use the land that was used for paddy fields as upland fields, they must first improve its drainage. Paddy fields with Lowland soil that have been covered in water often have a bluish color. This is because there is no oxygen in Lowland soil when it is covered in water, so the iron in the soil contains a high proportion of ferrous (divalent iron) ions (Fe2+<\/sup>). As Fe2+<\/sup> is pale green in color in an aqueous solution, paddy field soil is often bluish. As it dries out, oxygen spreads throughout the soil, turning the Fe2+<\/sup> ions into ferric (trivalent iron) ions (Fe3+<\/sup>), so the soil takes on a brown color.<\/p>\n So, what kind of soil is suitable for upland fields? In fact, Japan has a great deal of a type of soil that is rare worldwide: Andosols (Figure 3). Andosols account for as much as 31% of Japan’s total land area (the areas shown in bright brown on the soil map). Looking at all land on Earth, Andosols account for just 0.6%. As such, they truly are a soil characteristic of Japan.<\/p>\n Figure 3. <\/span>Andosol (Collected in Aya Town, Miyazaki Prefecture)<\/span><\/strong>Andosols are classified into six groups, one of which is Allophanic Andosols. Poorly crystalline clay minerals (allophane and imogolite) and humus have built up on a matrix of volcanic ejecta.<\/p>\n<\/div>\n It is precisely these Andosols that are suited to upland field cultivation. While they account for 31% of Japan’s total land area, that figure rises to around 47% when considered solely as a proportion of upland fields (ordinary fields, pastureland, and land under permanent crops). As they have good moisture retention capacity and permeability, the soil is soft and easy to plow.<\/p>\n But why do Andosols account for more than 30% of Japanese land area, when they make up less than 1% of all land on Earth? The reason lies in active volcanoes—that is to say, volcanoes that have erupted within the last 10,000 years and volcanoes that currently have active fumarolic activity. Andosols are soils formed from the deposition of volcanic ash. There are currently around 1,500 active volcanoes worldwide, as many as 111 of which are concentrated in Japan. The Japanese archipelago is located at a point where four oceanic and continental plates—the Pacific plate, the Philippine Sea plate, the Eurasian plate, and the North American plate—collide. Magma is formed when an oceanic plate sinks below a continental plate. The presence of so many active volcanoes is the reason why so much of Japan’s soil is made up of Andosols.<\/p>\n Japan’s Andosols are mainly located in the southern Hokkaido, northern Tohoku, Kanto, and Kyushu regions. It would be fair to say that this reflects the distribution of active volcanoes. The Japan Soil Inventory soil map shows that Andosols are located to the east of active volcanoes. This can be explained by the fact that volcanic ash emitted as a result of large-scale volcanic eruptions (eruptions in which the plume of ash reaches an altitude of 10,000 m) mainly travels and is deposited to the east of the volcano, due to the influence of winds called the westerlies. For example, the Andosols that make up a great deal of the soil surface in Tokyo, Kanagawa Prefecture, and other parts of the southern Kanto region were formed by the deposition of volcanic ash ejected during volcanic activity by Mount Fuji, Mount Hakone, and Mount Asama, among others.<\/p>\n As Andosols have many pores (holes or traces of plant roots) that formed during the process of the gradual deposition of volcanic ash, they drain very well. Another characteristic of soils derived from volcanic ash is their high content of active aluminum. Magma ejected by a volcanic eruption rapidly cools and decompresses, releasing the gas within the magma, which then forms volcanic ash and pumice containing a lot of bubbles. Rainwater flows into the bubbles in the volcanic ash after it reaches the ground, causing a great deal of aluminum—which does not normally dissolve very much—to leach out and bond with plant-derived organic matter in the soil. As a result, the soil gradually turns black in color.<\/p>\n The Japanese term for Andosol is kurobokudo<\/i>, which translates as “crumbly black soil.” It was in the wake of World War II that the English name was coined. When staff from the General Headquarters of the Supreme Commander for the Allied Powers carried out resource exploration and soil surveys of Japan’s territory, they were astonished to discover a type of black soil they had never seen before. Upon asking Japanese people what it was, they were told it was ando<\/i> (dark soil). Accordingly, they combined the Japanese word ando<\/i> with the suffix “sol,” which is derived from the Latin word solum<\/i>, meaning soil.<\/p>\n Whereas Andosols can now be described as fertile soils suited to upland field cultivation, they were once barren soils ill-suited to farming. This was because the active aluminum in which Andosols abound has a very powerful ability to absorb phosphate. Moreover, in humid climatic conditions such as those found in Japan, calcium and other minerals are lost from the soil when it rains, acidifying the soil. Phosphate ranks alongside nitrogen and potassium as one of the three macronutrients for crops. As it absorbs very strongly to active aluminum in the soil when it is in this acidic state, it cannot be absorbed by plant roots. As a result, crops do not thrive. On the Omiya Plateau during the Edo period (1603–1868), for example, farmers sought to overcome this problem by transporting rich, non-Andosol soil from riverbanks to improve the soil in their fields. They also supplemented the deficient phosphates by applying large quantities of organic fertilizer.<\/p>\n While both are black soils, this is something that differentiates Andosols from the Chernozems found across the huge wheat-producing area of Ukraine, where “Chernozem” means “black soil” in Russian. A byword for fertile soil, Chernozems are calcium-rich, neutral to mildly alkaline soils. As calcium forms loose bonds with plant-derived organic matter and builds up, the soil turns black. As calcium is a crop nutrient in its own right, it keeps the soil at a neutral pH level and provides an efficient supply of nutrients to crops.<\/p>\n Unlike Chernozems, acidic Andosols were barren soils. They were the bane of many producers’ lives. As many people will know from his poem Be Not Defeated by the Rain, poet and author of children’s stories Kenji Miyazawa provided agricultural guidance to farmers while cultivating his own fields. At Morioka Imperial College of Agriculture and Forestry (now the Faculty of Agriculture, Iwate University), he undertook soil research under the tutelage of Professor Toyotaro Seki. Professor Seki was one of the leading soil scientists in academic circles at the time, and served as the first president of the Japanese Society of Soil Science and Plant Nutrition. Most of the diluvial terraces in Iwate Prefecture are covered in Andosols, making the land acidic and barren. Accordingly, Kenji Miyazawa undertook research into a technique called acidity correction, to reduce the soil’s acidity. In his graduation thesis, entitled “The Value of Inorganic Elements in the Humus for Plants,” he reached the conclusion that soil-burning methods were means of turning Iwate’s Andosols into fertile soil. This shows how unsuitable Andosols were for agriculture back then, and how much improvement such soils required. It was after the war that the situation changed significantly. This is because phosphate-based chemical fertilizers in the form of calcium superphosphate and fused phosphate fertilizers became readily available.<\/p>\n Once chemical fertilizers entered widespread use, Andosols were increasingly used for upland field cultivation. As these soils are formed from volcanic ash, they do not contain any stones. They are also well-drained, making them suitable for growing root vegetables. The fact that wheat and soybeans are produced in the Andosols that stretch across the Tokachi Plain in Hokkaido can also be attributed to not only the climate conditions, but also the fact that wheat and soybeans do not require much water. In southern Kyushu, centered on Kumamoto Prefecture, production of the root vegetables such as sweet potato and daikon radish is flourishing in the area’s Andosol fields.<\/p>\n The first thing to assess when thinking about a nation’s food security is its soil resources. Japan was early in drawing up soil maps. The Meiji government invited German pedologist Dr. Max Fesca to Japan in 1882, and the Agronomic Map of the Kai-Province<\/i> was completed under his guidance three years later. Charting the soils of Kai Province (modern-day Yamanashi Prefecture), this was Japan’s first soil map to be drawn up from a scientific viewpoint. In addition, a preliminary soil map of Japan was exhibited at the 1889 International Exposition in Paris to tremendous acclaim.<\/p>\n It is thanks to the efforts of such pioneers that we were able to complete the Japan Soil Inventory, and we have supplied the soil map data in the Inventory to other websites. For example, there is a website that calculates how much CO2<\/sub> is stored in soil. Soil carbon storage, in which carbon absorbed from the atmosphere is locked in the earth in the form of soil organic matter, plays a major role in measures against global warming. Our data is used by this website, as well. Japan Soil Inventory data is also used to calculate the optimal quantity of fertilizer. The amount of fertilizer leached is determined by soil temperature and moisture content. There are a number of websites that calculate the appropriate quantity of fertilizer, which use our soil property data as well as data for moisture content and soil temperature estimated from air temperature and the like. We ourselves have created an app for visualizing element supply from various organic amendments, which is used by agricultural promotion agencies, among others. In around 70 cases where this app has been used to manage fertilizer use over the last three years, the effective use of manure and other organic soil amendments has succeeded in roughly halving chemical fertilizer use. As well as cutting costs, this is reducing the burden on the environment.<\/p>\n However, soil does change in response to such factors as land use and natural disasters. In some places the layer of black soil that was as much as 80 cm deep 50 years ago has been washed away, exposing the next layer down. In other words, more than 1.5 cm of soil has been lost per year in those places. In recent years, the whole of Japan has experienced torrential rain due to climate change, so the soil has likely changed quite a lot as well. While we have scaled down our work, we are still gathering the latest soil data from 1,000–2,000 sites per year (Figure 4). In addition, today we are able to use supercomputers and AI to estimate the process of changes in soil properties, which could not be assessed using older technologies. Making full use of these new technologies to analyze the latest survey results, we are continuing our efforts to further increase the accuracy of the Japan Soil Inventory soil map.<\/p>\n Figure 4. <\/span>Conducting a soil survey<\/span><\/strong>Soil is surveyed by digging a hole to a depth of 1 m. Part of the process involves creating a solidified specimen (soil monolith) of the cross-section of soil in its natural state. NARO’s Natural Resources Inventory Museum exhibits around 100 soil monoliths, which are around 20 cm wide and 1 m tall.<\/p>\n<\/div>\n What kinds of soil exist in which locations? A website called the Japan Soil Inventory provides answers to questions just like these. It is a digitized version of the Soil Information Web Viewer developed by the National Agriculture and Food Research Organization, which covers the whole of Japan, and it provides users with an at-a-glance understanding of the distribution of soil across the country, which has 381 different types of soil when soil on non-agricultural land is also included. As soil has a major influence on agricultural crop production, understanding which soils are suitable for cultivation is absolutely crucial. Ensuring the stable availability of soil resources is an issue that should also be top of mind from the perspective of a nation’s food security.<\/p>\n","protected":false},"author":2,"featured_media":2657,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[18],"tags":[],"class_list":["post-2661","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-nature"],"acf":{"author":"composition by Takeaki Kikuchi","intro":" What kinds of soil exist in which locations? A website called the Japan Soil Inventory provides answers to questions just like these. It is a digitized version of the Soil Information Web Viewer developed by the National Agriculture and Food Research Organization, which covers the whole of Japan, and it provides users with an at-a-glance understanding of the distribution of soil across the country, which has 381 different types of soil when soil on non-agricultural land is also included. As soil has a major influence on agricultural crop production, understanding which soils are suitable for cultivation is absolutely crucial. Ensuring the stable availability of soil resources is an issue that should also be top of mind from the perspective of a nation’s food security.<\/p>","person":[{"acf_fc_layout":"personcontent","personimg":2656,"personsholder":"Senior Researcher, National Agriculture and Food Research Organization (NARO)","personname":"Yusuke Takata","persondetail":"Graduated from Obihiro University of Agriculture and Veterinary Medicine in 2001. In 2007, he successfully completed a doctoral program at Kyoto University’s Graduate School of Agriculture. After holding a Research Fellowship for Young Scientists at the National Institute for Agro-Environmental Sciences and then serving as a senior researcher at the same institution, he took up his current post in 2016. That same year, he received the Japan Award for Young Agricultural Researchers from the Ministry of Agriculture, Forestry and Fisheries for compiling a digital soil map and a distribution map showing the concentration of radioactive materials in agricultural land."}],"issue":2638,"custom_css":""},"_links":{"self":[{"href":"https:\/\/healthist.net\/en\/wp-json\/wp\/v2\/posts\/2661","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/healthist.net\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/healthist.net\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/healthist.net\/en\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/healthist.net\/en\/wp-json\/wp\/v2\/comments?post=2661"}],"version-history":[{"count":0,"href":"https:\/\/healthist.net\/en\/wp-json\/wp\/v2\/posts\/2661\/revisions"}],"acf:post":[{"embeddable":true,"href":"https:\/\/healthist.net\/en\/wp-json\/wp\/v2\/issue\/2638"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/healthist.net\/en\/wp-json\/wp\/v2\/media\/2657"}],"wp:attachment":[{"href":"https:\/\/healthist.net\/en\/wp-json\/wp\/v2\/media?parent=2661"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/healthist.net\/en\/wp-json\/wp\/v2\/categories?post=2661"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/healthist.net\/en\/wp-json\/wp\/v2\/tags?post=2661"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}Updating the distribution in around 400,000 unsurveyed areas<\/h2>\n
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<\/small><\/p>\nThe appropriate crops differ according to the properties of the soil<\/h2>\n
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<\/small><\/p>\nAndosols formed from volcanic ash have good drainage<\/h2>\n
Chemical fertilizer use roughly halved in some cases<\/h2>\n
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<\/small><\/p>\n