The most approachable man! Xu Zhengyi, the "soil librarian", went all over Taiwan to dig the earth, digging deep into the soil and diagnosing the meaning of agriculture.

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Others circle the island to challenge themselves, while Hsu Cheng-Yi circles the island to get to know the soil of the whole of Taiwan. This professor of agrochemistry at National Taiwan University, who has studied soil investigation all his life, recently took over the soil museums that preserve soil all over Taiwan from his predecessors, hoping to enable more people to really understand Taiwan's "land."

Xu Zhengyi, who has traveled all over Taiwan and all over the world for more than 20 years, can be called the most approachable man. Hsu Cheng-Yi says that soil not only provides crop growth, but is also closely related to human life. From food to utensils, cosmetic care products, and so on, there is knowledge of soil everywhere, and soil constitutes human civilization. It also gives places a unique "soil."

Xu Zhengyi (Photography / Lin Yijun), a professor in the Department of Agricultural Chemistry of National Taiwan University, took over the third generation of soil Museum curator and guarded the previous research achievements.

The gentle Xu Zhengyi is the son of a peasant family in Zhenggang. His hometown is in Meishan, Chiayi. In the soil science class, the students can always hear about his childhood with oranges. "I have been very close to the soil since I was a child, but the key to my decision is my mentor." The teacher he calls his mentor is Chen Zunxian, a professor in the department of agrochemistry at National Taiwan University who retired in 2017.

Hsu Cheng-Yi University studied in the department of agrochemistry at National Taiwan University. at that time, the department of agrochemistry was divided into two groups, namely: soil fertilizer and agricultural manufacturing, and he studied in the soil fertilizer group. University began to study with Professor Chen Zunxian at 04:00. "I didn't have any great ideas at that time, just because the teacher said that few people were doing soil survey, and it was a blue sea, so I decided to go this way."

The decision made him one of the few soil surveyors in the country. Walking into the recently reorganized soil museum, Hsu Cheng-Yi says that this museum is the result of soil investigation handed down from generation to generation. Master Zhang Zhongmin passed it on to his mentor Chen Zun-hsien, and he took over from Chen Zun-hsien and became the "owner" of the third-generation museum.

The investigation around the island took great pains, carrying heavy soil samples on foot.

Soil samples from all over Taiwan can be seen in the museum, from estuarine alluvial plains and tropical platforms to high-altitude mountain areas, and some soil samples have even been preserved from the Japanese occupation period. There are many on-the-spot photos of soil investigations in the past on the wall. "this is me when I was in college. I went to do soil survey with teacher Chen Zunxian." He in the picture, and now he, his exuberant appearance has not changed.

Soil survey is quite hard work. Hsu Cheng-Yi says that the soil survey in Taiwan began after 1960. Up to now, although the tools are slightly different, the survey method has always been the same. "some places are so remote that you have to use a four-wheeled car and walk to get there." He recalled that when he went to investigate South Dawu Mountain, he took the ancient flooded camp road with an annual rainfall of more than 4000 millimeters. it was muddy all the way. He left at two o'clock in the afternoon and walked for four hours before it was dark.

"it's easy to go up the mountain, but it's even more tiring to go down." Xu Zhengyi said with a smile that he had to bring soil samples with him on his way back. If he was going back on foot, he would not dare to sit down even if he was tired, "because he had to stand up with more than ten or twenty kilograms of luggage and soil samples on his back after the rest." It's harder, so when you're tired, you look for trees or rocks to lean on.

In 1992, Xu Zhengyi (1 from right) and his mentor Chen Zunxian (2 from right) conducted a soil survey (photo courtesy of Xu Zhengyi). There were so many soil survey tools that the excavation depth was up to 2 meters.

If you want to do good work, you must first sharpen its tools. Soil investigation must bring all kinds of "furniture", including shovels or spades for digging, wooden frames for making section specimens, surface glue, and so on, of which the most conspicuous is a soil drill. T-shaped soil drills can be drilled into the soil to dig out soil samples of different depths, and the soil drills can also be lengthened as needed, up to 2 meters.

The first question encountered in soil investigation is: "where are we going to dig?" Hsu Cheng-Yi explains that soil is a natural body occupying volume on the surface, and it will change over time due to the remains of animals and plants and the effect of climate. "even if they are all in the same town, the soil quality may be different in the east, south, west and west."

Therefore, where the soil should be collected depends on the purpose of the investigation. If it is a census, it should be intensive sampling in the same area and carried out in multiple areas; if it is a specific area survey, only part of the soil samples in that area can be taken. The researchers drew the results of past surveys into a soil map of Taiwan, which is divided into 11 colors, representing 11 soil classes, from south to north and west to east.

Soil cross-sectional sampling requires digging from the soil surface to the rock layer (photo provided / Yang Jiayu) soil classification should not only grasp a handful of soil, but also evaluate the surface layer to the rock layer.

What is meant by "soil class"? Xu Zhengyi said that the soil class is the basic way of soil classification, just like the genera and species of the family Phylloidea in biological classification. At present, the common classification method in the world is the 12 soil class classification of the United States. To be classified into which soil class, there are many quantitative criteria, such as color, texture, pH value and so on.

"as soon as someone hears that I am studying soil, they will grab a handful of soil in front of me and ask me, but in fact, it is very difficult to answer," Xu Zhengyi said with a smile, because most people only come into contact with the surface of the soil, and their hands grasp only a very small part of the soil. This is why soil samples need to be dug deep, sometimes as deep as several meters. "A handful of sandy soil is not classified systematically. it has to be classified from the soil surface to the parent rock."

Xu Zhengyi took out the photos of past soil samples to show that there are six layers of soil under the soil surface, which are OAEBCR layer, upper three layers, litter layer, humus layer and E layer. Further down the B layer is the deposition layer, the C layer is the weathering layer, and the lowest R layer is the rock layer. "this kind of stratification is like the human head, chest, waist, abdomen and feet, just as people have to look at the overall condition before they can make a diagnosis or analysis, and so is the soil."

What are the criteria for classification? Do you watch it or touch it? Xu Zhengyi said that color, texture, particle size, water content, pH and so on are all important indicators. Touch with your hands can feel whether it is sand, loam or clay, the most intuitive is to see the color, can be divided into red soil, loess and black soil. Only the black soil is very general. Under the black soil, it depends on its texture and composition. For example, the black soil in Yangmingshan is volcanic ash, and the organic black soil bought by the florist is peat soil accumulated by biological residues. "