Agriculture and Science 2020/5

Soil Survey of Traditional Vegetable (Taro) Production Areas in Yamagata and Miyagi

Miyagi University, School of Food Science and Industry
Hideyuki Saito

Introduction

　In recent years, the rediscovery and reuse of traditional vegetables (local native species) has been active in all regions of Japan. Although there is no clear definition of "traditional vegetables," they are considered to be vegetables that (1) have been cultivated in a certain region for generations, (2) are seeded and bred by the growers themselves, and (3) are used in specific dishes or for specific purposes (Yamagata Native Crops Study Group, 2010). They are not only valuable genetic resources of the region, but also cultural heritage that conveys the history of the region to the present. In addition, their flavors are said to be closely related to the soil conditions of the region. In other words, their unique flavor is said to be difficult to obtain when cultivated in other regions.

　On the other hand, in Yamagata and Miyagi prefectures, there are various local varieties of taro. In both prefectures, taro stew parties are often held on riversides in autumn, and have become an autumn tradition. For example, in inland Yamagata Prefecture, beef is usually used in the soy sauce flavor, while pork is usually used in the miso flavor in Miyagi Prefecture. Although individual differences in taste and perception of flavor are likely to be significant, the influence of soil physical and chemical properties on flavor is not insignificant. In this paper, we conducted a soil survey of taro (a local native variety) production areas in Yamagata and Miyagi prefectures as a clue to considering the relationship between soil physical and chemical properties and flavor.

2. Major local taro species in Yamagata and Miyagi Prefectures

　First, a bird's-eye view of the main local taro species in Yamagata and Miyagi prefectures is presented. All of them are well adapted to the soil and climate of their respective regions, but their exact origin is not always clear. The taro is often characterized by its "stickiness" or "stickiness. Some people also cite the taro's inherent sweetness and the rich earthy aroma that permeates the nose.

　It is especially produced in a sandy loam community (Kado) along the Sukawa River. It is characterized by the reddening of the petioles at the edge of the ground, and has a sticky and fluffy texture when eaten as taro stew (Yamagata Native Crops Research Association, 2010). Although it was in danger of extinction for a time (Saito et al., 2001), it has recently been revived and has become a representative traditional vegetable of Yamagata. The place name "bado" means "bad soil" or "akudo," and refers to fertile land (Murakizawa District Promotion Association, 1989). Located on a fan-shaped area (sandy loam) of the Sugawa River (a tributary of the Mogami River), the soil is acidic and rich in minerals because water flows from the hot springs area of Zao.

　Jingoemon taro: This is a local variety that has been passed down from generation to generation by the Sato family of Osawa, Mamurogawa-cho, northern Yamagata Prefecture, under the family name "Jingoemon". This taro is considered to belong to either the red-bud variety or the karaimo variety, and when cooked in taro stew, it is soft and sticky to the touch, but has a light texture on the palate. However, the yield is a little lower than that of economic varieties.

　It is a local variety native to the Saranuma district of Sagae City, located in the center of Yamagata Prefecture. It is characterized by its smooth, sticky texture and subtle sweetness. The Saranuma area was frequently flooded during the Edo period (1603-1867), and fertile sandy loam soil was formed there (Yamagata Native Crops Research Association, 2010). The cultivation of the area is based on "crop rotation" and "soil improvement with organic materials," and other vegetables are planted in three- to four-year cycles, and compost is actively applied.

　Zao Town in southern Miyagi Prefecture is a major producer of taro in the prefecture, and various strains exist, with the Shimobetsutou area being particularly famous. Because of its topography, the Shimobetsudo area is less prone to frost damage, and the soil is typical volcanic ash soil. The potatoes have a sticky texture, and it is said that this stickiness cannot be obtained if the potatoes are grown in other areas.

　Ibano sweet potato is a local species that has been handed down in the Kami-Ibano district of Sanbongi-cho, Osaki City, Miyagi Prefecture. According to "Comprehensive Guide to Local Vegetables by Prefecture" (2002, No Bunbun Kyokai), it is called "Dodaru" type. It is soft and sticky, and is suitable for various dishes. However, its yield is slightly lower than that of economic varieties. It is characterized by its reddish pattern. It is important to note that once a field is planted, it should not be planted again for three years.

3. soil survey in various locations

　Soil samples (5 to 10 cm deep) were collected and analyzed for the following varieties: Kohime sweetpotato, Zao-cho (Shimobetsudo) native sweetpotato, and Ibano sweetpotato. Soil samples were also collected from a field in the Yagyu district, Taihaku-ku, Sendai City, for reference. This is because taro (variety unknown) was growing very vigorously in this area, and the petiole length was over 1.5 m. All sampling was conducted in the Yagyu district, Taihaku-ku, Sendai City, Japan. All sampling was conducted from August to September 2018 (Table 1).

4. physical properties of field plots

　The results of the survey are shown in Table 1. The field plots in the Saranuma area of Sagae City (the field plots of sweet potato "Kohime" were classified as brownish lowland soil, and the soil texture was sandy. The area has been plagued by floods since the Edo period (1603-1868), and fertile sandy loam has been formed every time a flood occurs (Yamagata Native Crops Research Association, 2010).

　The field plots in the Shimobetsudo district (native to Zao Town) were classified as humid black-bok soil, and the soil texture was clayey. The soil is clayey. Because the area is located at the foot of Mt.
　The field plots in the Kami-Ibano area of Sanbongi-cho, Osaki City (Ibano potato) were classified as brown lowland soil, and the soil was clayey. The lowland is located along the Naruse River and is prone to flood damage (according to interviews with growers).
　The Yagyu area is located along the Natori River in Taihaku-ku, Sendai City, and the field plots were classified as brownish lowland soil with clayey to loamy texture.

5. the chemistry of the field plots

　The results of the chemical properties analysis are shown in Table 2.

　1) Saranuma area, Sagae City (Kohime potato); pH was almost neutral at 6.8. Nutrient relations were high with 270 mg/100g of effective phosphoric acid and 280 mg/100g of exchangeable potassium. Potassium saturation (26%) and base saturation (105%) were also conspicuously high. On the other hand, the Murakisawa bado district in Yamagata City has acidic soil. It is said that the texture of Kohime sweetpotato is "sticky and smooth" and that of Kadato sweetpotato is "soft and melting" (Yamagata Native Crops Research Association, 2010). It will be necessary to compare these differences in texture in the future in terms of varietal characteristics and soil differences.

　(2) Shimobeto area, Zao Town (native to Zao Town); 7% of humus was conspicuously high and the soil was "soft and fluffy". The phosphate absorption coefficient was high at 1590. The high phosphate absorption coefficient indicates that phosphate is easily adsorbed into the soil even if it is applied, and the soil was considered to have the chemistry of typical black soil. The low exchangeable calcium (210 mg/100 g) and magnesium (17 mg/100 g) were also notable in terms of nutrients.

　3) Ibano area, Sanbongi-cho, Osaki-shi (Ibano sweet potato); The soil was not fertile, but the low height and small size of the grass indicated that adequate nutrients were being supplied to the area.

　(4) Yagyu area, Taihaku-ku, Sendai City; pH was almost neutral at 6.7. The effective phosphate was slightly high at 92 mg/100 g, and the exchangeable magnesium was slightly low at 40 mg/100 g. The ammonium nitrogen was high at 6.7 mg/100 g, and the ammonium nitrogen was low at 6.7 mg/100 g. Ammonia nitrogen
The nitrate nitrogen and nitrate-form nitrogen were 0.2 mg/100 g and 0.4 mg/100 g, respectively, which was a little surprising considering the vigorous growth of taro in the area.

Summary

　In recent years, traditional vegetables have been attracting attention as genetic resources and as part of regional revitalization efforts (Matsumoto, 2012). Accordingly, it has become clear that many native species of taro remain in relatively fertile areas in river basins (Matsumoto, 2012).

　In an attempt to summarize the survey, the following is a summary of the results.
　(1) Soil pH suitable for growing taro is weakly acidic to neutral, ranging from 6.6 to 7.0 (Kuboi, 1978). Soil pH in the Yagyu district of Taihaku-ku, Sendai City and the Saranuma district of Sagae City were 6.7 and 6.8, respectively, which were suitable for growing taro, while those in the Shimobeto district of Zao Town and the Kami-Ibano district of Sanbongi, Osaki City were 5.6 and 6.0, respectively, which were considered slightly lower than the pH of the soil.

　(2) Humus (%) was high in the Shimobeto district of Zao Town and low in the other districts. According to Kono and Kurinami (1992), taro cultivated in humus-rich humid black box soil had higher fructose, glucose and sucrose contents.

　(3) Regarding soil type, taro grown in fine-grained strong gley soil is considered to have low content of each sugar and hydroxyproline. Hydroxyproline is a soluble sweet amino acid and is presumed to be related to eating quality (Kono and Kurinami, 1992). The soils in the Saranuma district of Sagae City, the Kami-Ibano district of Sanbongi in Osaki City, and the Yagyu district of Taihaku-ku in Sendai City are brownish lowland soils, not gley soil, so it is highly possible that the soil type affects the eating quality of the grapes.

　(3) Regarding soil chemistry, mineral richness was felt in the Saranuma district of Sagae City.

　As described above, although all of the taro varieties investigated in this study were renowned for their production area and reputation for excellent taste, no clear relationship was found between the soil properties of each taro production area and the taro varieties. This suggests that the effects of soil physical and chemical properties on the growth of taro and its flavor and taste may not necessarily be in sync with each other. Some producing regions have their own secrets in soil preparation, and some of the respondents said that it is a "trade secret" so to speak.

　According to Kono and Kurinami (1992), variety has the greatest effect on the sugar content of taro, followed by soil type. In addition, the classification of eating quality in taro can be broadly divided into "slimy type" and "hot and flaky type," which is a matter of individual preference (Matsumoto, 2012). Thus, the flavor and taste of taro are considered to be evaluated based on a complex interplay of various factors.

　It is highly likely that the physical and chemical properties of the soil affect the flavor and taste of taro, but since the sampling in this study was limited to a very small area in each production area, it was not possible to make a good relationship between the two. Further studies will clarify this aspect by increasing the number of samples, analyzing the components of the harvest, and carefully conducting sensory tests.

Acknowledgements

　Ms. Miona Takanai (from Yamagata Prefecture), a student of the Department of Food Resources Development in the Food Science and Technology Group of our university, gave us her opinions on the selection of the survey site and on the tastes and flavors of the taro. We would like to express our gratitude to her.

Bibliography

1) Yamagata Native Crops Study Group. 2010. talking fields: Yamagata's native crops are living cultural assets.
In the corner of a field in Kokoka II-. 84-85. 88-89. Yamagata University Press.
(2) Murakizawa Area Promotion Association. 1989. murakizawa Encyclopedia. 185. Yamagata City Murakizawa Community Center.
3) Saito H., Chisaka T., Oguro H., Takahashi N.　2001. Native species and useful genes in Miyagi Prefecture.
A Survey of the Sources. Journal of Miyagi Junior College of Agriculture. 49: 59-66.
4) Takii Seed Co. 2002. 2002.
5) Matsumoto, M. 2012. taro - From cultivation to storage and seed potato production. 36.42.
6) KUBOI, Ei. 1978. Effect of growing conditions on the growth of satoimo (Arachis hypogaea). Tropical Agriculture. 21(3);183-188.
7) Michiyoshi Kohno and Satoshi Kurinami, 1992. content of soluble sugars and hydroxyproline in taro tubers and their
Factors of its Variation. Japanese Journal of Soil and Fertilizer Science. 63 (3); 196-203.

Fertilizers and nutrients:
　Coated phosphorus ammonium nitrate (long, high control, Nutricote)
　Characteristics of (Part 1)

Shibata Professional Engineers Office
Masaru Shibata

(1) What is coated phosphorus nitrate ankari (long, high control, Nutricote)?

　Coated phosphorus-nitrite potassium is the generic name for fertilizers coated with nitrate-based compound fertilizers (phosphorus-nitrite potassium, NK compound) containing about 50% nitrate-form chisso in a polyolefin resin. Typical brands are listed in Table 1. ECOLONG's coatings are photo-disintegradable and microbially degradable.
　Many other brands containing trace elements and with elution periods exceeding 270 days are commercially available.

(2) Properties of thiessotropic fertilizers

　Soil particles have a cation exchange capacity (capacity to adsorb cations: CEC), which affects the movement of cation nutrients through the soil. On the other hand, the anion exchange capacity of soil is small. Ammonia-form nitrate (NH4+), which is produced by fertilization or by mineralization of organic nitrate, is adsorbed by soil particles, so there is little movement in the soil, but the anion nitrate moves (diffuses) in the soil water without being adsorbed by the soil. Urea is not an electrolyte like ammonium sulfate or ammonium nitrate, so it is not affected by soil CEC, but it is rapidly decomposed into ammonia and carbon dioxide by the urease enzyme urease present in the soil, resulting in the same behavior as ammonium nitrate (Table 2).

(3) Changes in the Form of Chisso in Soil

　On land, ammonia-form nitrogen is converted to nitrate-form nitrogen by the action of nitrifying bacteria, i.e., (1) nitrite-forming bacteria (Nitrosomonas), which oxidize ammonia-form nitrogen to nitrite, and (2) nitrate-forming bacteria (Nitrobacter), which oxidize nitrite to nitrate. These microorganisms take up ammonia- and nitrite-form nitrogen in their bodies and use the energy they acquire to grow, and are important microorganisms that supply nitrate-form nitrogen to field soils (Figure 1).

　Since most field crops are nitrate-loving plants, nitrification has a significant impact on crop production. When nitrification does not occur smoothly, crops do not grow well, and fertilized ammonium-form nitrogen accumulates in the soil as ammonium ions, making it easy for excess ammonia damage to occur.

　The degradation (mineralization) of urea occurs by the degrading enzyme urease, which is secreted by the microorganism outside the fungus, as in equation (1).
　①(NH2) 2CO + H2O → 2NH3 + CO2
Next, as shown in equation (2), the ammonia-form chisso generated undergoes nitrification by nitrifying bacteria and undergoes nitrite-form chisso to become nitrate-form chisso.
　2) 2NH3+3O2→2HNO2+2H2O
　　2HNO2+1/2 O2→2HNO3

　The rates of (1) urea mineralization and (2) nitrification in soil are often out of sync, with urea degradation rate > nitrification rate. External factors that affect (retard) the nitrification rate include soil temperature (low temperature) and soil disinfection, which reduce the activity of nitrifying bacteria (Figure 2). Therefore, when urea is applied, it is necessary to pay attention to the nitrification trend in the soil.

　The compound resulting from the decomposition of urea is thought to exist in the soil in the form of ammonium carbonate. Ammonium carbonate, which is inherently slightly alkaline, is easily autolysed into ammonia and carbon dioxide. If urea-derived ammonia is not nitrified quickly, it can easily cause ammonia-induced root burn symptoms and ammonia gas injury.

　This phenomenon does not occur with ammonium sulfate. Ammonium sulfate is a weakly acidic compound in which ammonium ions are combined with sulfate ions, so it does not form free ammonia. Urease is a unique enzyme that degrades urea in the pH range 6.5 to 7.5 and is active even in alkaline conditions. In this pH range, the activity of nitrifying bacteria decreases while that of urease does not, which is one of the reasons why the rates of urea degradation and nitrate formation are not synchronized.

　The registered name of chemical compound fertilizers made from urea has "urea" appended to it, for example, "urea sulfonated phosphorus ammonium 48," to distinguish it from "urea sulfonated phosphorus ammonium 0000," which does not use urea (Figure 3). This is also an indication to let users know that, in the field where alkaline materials such as bitter lime are often applied to correct acidity, they should take extra days before planting to avoid ammonia damage when using a chemical compound fertilizer containing urea.

　In humans, there have been cases of hyperammonemia due to urea decomposition in urine by bacteria that have infected the urinary tract and produced ammonia, resulting in consciousness disorders. Free ammonia is toxic to all living organisms.

(4) Nutricote, going into space!

(Photo 1)

　Photos of lettuce being grown on board a spacecraft and eaten by the crew can be found on the Internet.
　Growing vegetables in space is probably intended to ensure self-sufficiency of fresh vegetables for a long stay in space, but the healing effect cannot be overlooked. It is thought that this is one of the methods to regulate the increase of carbon dioxide concentration in the spacecraft by fixing a part of carbon dioxide gas, which is estimated to be generated from the breath of an adult male at about 0.7 kg/day/person, with plants, and the generated carbon dioxide gas is absorbed and separated, and released outside the spacecraft.

　The fertilizer applied to the medium is Nutricote 18-6-8 + ME (trace element) type 270 from Jaycam Agri Co. Since the in-vessel temperature was maintained at 21-25°C and the microbial activity of the medium was not high, nitrification of ammonia-form chisso was slow. In order to harvest well-grown lettuce, a compound coated fertilizer that contains and controls the supply of other fertilizer components and trace elements in addition to nitrate-form chisso, which lettuce prefers, is required. Nutricote was selected because of its superior leaching control performance in comparison with similar coated fertilizers made in the U.S.A. NASA is also conducting trials on other crops.

　This is due to the fact that vegetables cannot grow without nitrate nitrate, whether on earth or in space (Table 3). Sooner or later, Nutricote will go to Mars! may come.

(5) Signaling effects of nitrate ions

　Komatsuna (a nitrate-loving crop) can hardly utilize ammonium nitrate, but it shows dramatic growth when nitrate-form nitrate is added at about 11 TP3T (signaling action of nitrate ions). In addition to its role as a nutrient, nitrate plays a role in activating nitrate metabolism in plants, which utilize ammonia-form nitrate as a nutrient (Fig. 4).