Agriculture and Science 2020/12

Fertilization of Municipal Solid Waste Molten Slag and Application Development

Shizuoka University, Faculty of Agriculture
Department of Applied Life Sciences
　　　Associate Professor Takashi Ichiya

Introduction

　In 2006, JIS standard for molten slag was established, and quality control of molten slag is now in progress. In recent years, the majority of molten slag has been utilized as construction and civil engineering materials, mainly as aggregate for secondary concrete products, aggregate for asphalt mixtures, and aggregate for backfilling. On the other hand, molten slag is expected to be applied to other industries where high value-added and stable market scale can be expected, especially in the agricultural field. This is because the main component of molten slag is silicic acid, and its composition ratio is the same as that of "Silical" (lime silicate fertilizer) produced from blast furnace water-breaking slag, which is familiar as an agricultural material.

　Since 2013, our research group has been working with Shizuoka City and Nippon Steel & Sumikin Engineering Corporation (now Nippon Steel Engineering Co., Ltd.) to convert molten slag into fertilizer through a series of demonstration tests. As a result, on March 27, 2017, molten slag produced at the Nishigaya Cleaning Plant in Shizuoka City, Shizuoka Prefecture, was approved by the Ministry of Agriculture, Forestry and Fisheries as a fertilizer for the first time in Japan, and is now commercially available as SK Keikal by JA Shizuoka Keizairen (Figure 1). The characteristics and adaptability of molten slag as an agricultural material were evaluated through demonstration tests on rice plants that use silicic acid as a useful element.

2. effect of silicon on plants

　Silicon (Si) is an essential element for animals, but it is not recognized as an essential element for plants and is not necessarily required by all plants. However, silicon is considered a useful element for plants because the application of siliceous fertilizers improves or has a positive effect on the growth of many plants, especially grasses.

　The beneficial effects of silicon on plants are diverse. For example, the accumulation of large amounts of silicon in rice leaf blades improves mechanical strength and enhances photosynthesis by improving the photosensitive state of the leaves. In addition, the accumulation of silicon in the stem increases stem strength, which in turn improves resistance to overturning. This directly leads to a reduction in damage caused by typhoons during the harvest season.

　In addition, accumulation of silicon in the plant body is effective in improving resistance to various stresses. For example, in addition to reducing abiotic stresses such as rice blast, powdery mildew, and insect damage such as leafhoppers and fungus, silicon also contributes to the reduction of non-biotic stresses such as nutrient deficiencies, low temperature, high temperature, and drought stresses. These facts indicate that silicon has an effect on plants to reduce combined stresses, and as a result, contributes greatly to yield increase of crops.

3. demonstration test in rice paddies

　We conducted paddy rice cultivation tests using molten slag from the Nishigaya Cleaning Plant in Shizuoka City, Shizuoka Prefecture [treatment method: shaft furnace type (coke bed type) gasification and melting method] in accordance with the test areas shown in Table 1.

　Rice paddy cultivation trials were conducted in rice paddies at two locations with different cultivation histories: in 2013 and 2014 in rice paddies in the Faculty of Agriculture, Shizuoka University (Oya, Suruga-ku, Shizuoka City, Shizuoka Prefecture), and in 2017 in rice paddies in a field affiliated with Shizuoka University (Karijuku, Fujieda City, Shizuoka Prefecture). Rice seedlings were transplanted into the paddy field (30 cm between plants and 15 cm between rows). Base fertilizer and ear fertilizer were applied according to the Shizuoka Prefecture's fertilizer standard (Koshihikari on flat land) at rates of 2 kg, 3 kg, and 3 kg/ 10 a of nitrogen (N, ammonium chloride), phosphoric acid (P, superphosphate lime; P2O5), and potassium (K, potassium chloride; K2O), respectively. The first ear fertilizer was applied at 2 kg, 0 kg, and 2 kg/10 a. The second ear fertilizer was applied at 1 kg, 0 kg, and 1 kg/10 a of N, P, and K, respectively.

　Cultivation trials at Shizuoka University were conducted under constantly waterlogged conditions, while cultivation at the Fujieda field was conducted under medium-dry conditions for about two weeks. Throughout the growing period, each agronomic trait (culm length, ear length, number of ears, etc.) was surveyed (10 individuals were randomly selected from each block), and a yield survey was conducted by tsubo-harvesting. The traits were randomly divided into five blocks within each treatment, and the yield per 10a was calculated from the average of the yield per tsubo mowing. The silicic acid (Si) content in the hemp leaves and rice husks was calculated by the gravimetric method using wet ashing followed by drying. The amount of molten slag (soluble silica: 32%) applied was calculated from the standard amount of Silical (soluble silica: 34%) applied of 120 kg per 10 a. (All of these values were measured and analyzed before the test).

　Table 2 summarizes the results of the last three years' trials. Although there was not much difference in culm length and ear length due to slag or silica fertilizer application compared to the control, a significant increase in ear number was observed, especially in the 2013 trial. In addition, there was a significant increase in each yield trait with siliceous fertilizer application compared to the control. In particular, straw weight (biomass weight), hull weight, and weight of polished brown rice increased with the amount of siliceous fertilizer applied, with the highest increase observed in the area fertilized with twice the amount of slag. The highest increase was observed in the area with 2x slag fertilization. The increase effect was further enhanced by the continuous application of fertilizer in the second year.

　The paddy field in the Faculty of Agriculture, Shizuoka University, which was used for this study, had been completely neglected for many years and had not maintained its function as a paddy field until immediately before the test. Therefore, we stripped all of the surface soil of about 10 cm, along with weeds, just prior to the cultivation test, and began the test cultivation by plowing the field anew. This meant that there was no silicon supply to the paddy field and that a large amount of silicon was taken out from the paddy field. Therefore, the effect of siliceous fertilizer application was probably very pronounced in the first-year trial. On the other hand, the 2017 results from the Shizuoka University farm were conducted in paddy fields where rice was continuously cultivated, so the effect of silica fertilizer seems to be somewhat lower than in the Shizuoka University Faculty of Agriculture, but the yield increase of about 101 TP3T was still observed in the slag-added area.

　Overall, the above results indicate that the application of siliceous fertilizers has a positive effect on rice growth, and the effect is equal to or greater than that of conventional silical fertilizers. Although not mentioned in this report, the content of toxic metals such as cadmium, lead, and mercury in brown rice due to slag application were all below the standard values, indicating that there were no adverse effects of slag and its safety was confirmed.

4. Conclusion

　In modern human activities, we are constantly troubled by the problem of waste generation. Waste disposal is also one of the issues in disaster recovery. The shaft furnace type gasification and melting furnace, which melts rather than burns garbage, can safely process garbage of all kinds of materials and contributes greatly to the reduction of garbage volume. The conversion of molten slag derived from municipal solid waste into fertilizer, which we have demonstrated, can be called the ultimate in recycling. In September 2015, the United Nations General Assembly adopted the Sustainable Development Goals (SDGs) consisting of 17 goals and 169 targets as an action plan for people, the earth, and prosperity, and efforts to achieve the SDGs are being promoted by industry, academia, and government alike. The Sustainable Development Goals (SDGs) are a set of 17 goals and 169 targets.

　When considering the SDGs from the perspective of food, it is clear that many things are indeed relevant. The recent global environmental changes and the COVID-19 pandemic have had a tremendous impact on the economic and industrial worlds. However, while there is an urgent need to build a system for increasing crop yields that can withstand explosive population growth and dramatic global environmental changes, achieving this goal will be extremely difficult. In other words, the key is to break through the current status quo of agricultural production and build a sustainable agricultural system that can efficiently utilize the earth's finite resources. To achieve this, we need to establish efficient cultivation methods that require less water, and at the same time, provide tolerance to biotic and abiotic stresses so that healthy growth can be maintained even under adverse environmental conditions. Silicon is also a key nutrient for solving the above problems.

　We have demonstrated the effectiveness of molten slag as a siliceous fertilizer through cultivation trials since 2013. In order to further demonstrate the effectiveness of molten slag, we are currently testing its effect on the growth of various plants in addition to other grass species (e.g., water bamboo and sugarcane), with positive results obtained in all cases (Figure 2). In addition to fertilizers and biological residues, rainwater and irrigation water also supply nutrients to the paddy fields. Silicic acid, which has a negative nutrient balance in paddy fields, is an important element in rice cultivation and needs to be supplied continuously to maintain the health of rice plants.

　On the other hand, it has been reported that the silicate content in soil and the supply of silicate from water have been decreasing in Japan in recent years. This is related to various factors, but the main factor is considered to be the yearly decrease in the amount of siliceous fertilizers applied. Silicon is the only nutrient that does not cause plant damage due to excessive application, as is often observed with other nutrients. As mentioned above, the promotion of the use of siliceous fertilizers, including molten slag, will be key to maintaining stable quality and production in response to the poor growth of crops caused by abnormal weather conditions that are occurring on a global scale.

Labor-saving fertilization with slow-release fertilizers in potted flower cultivation

Jcam Agri Corporation Kyushu Branch
Korisakae Noriaki

Introduction

　Flowering plants are plants that enjoy their flowers and leaves, and are classified into cut flowers, bulbs, potted flowers (hereinafter referred to as "potted flowers"), and flower bedding plants. Among these, cut flowers such as kiku (Asteraceae) are widely produced, accounting for 81.31 TP3T of the total cultivated area of 17,440 ha in Japan. Potted flowers, on the other hand, are very popular as a luxury item to enjoy beautiful flowers and leaves indoors, but the cultivated area in FY 2008 was only 1,605 ha, less than 101 TP3T of the total (Table 1).

　Potted flower sales were probably flourishing around the height of the bubble economy, but since then, sales of potted flowers have been declining except for orchids such as the orchid. This is due to the decline in consumption due to the economic slowdown, as potted flowers themselves are a luxury item, but it is also thought to be due to the special characteristics of potted flower cultivation, such as the large number of products and varieties, the delay in basic research, and the fact that potted flowers are grown in pots rather than in the soil. In order to ensure healthy growth, it is a priority to provide a proper growing environment in pots, and in particular, sufficient attention must be paid to the physical strength of the pot to support the plant body, the nature of the culture medium that provides moisture and oxygen essential for growth, and fertilizer application that provides almost all the nutrients. The following are some of the most important factors to be considered
　Here, I would like to discuss the characteristics of the culture medium required for potted flower cultivation and labor-saving fertilization techniques using slow-release fertilizers.

2. conditions as culture medium for potted flowers

　Potted flower cultivation is one of the root-zone-restricted cultivation methods in which flowering plants are grown in a limited space inside a pot. In limited root zone cultivation, the amount of soil per potted flower is smaller than in soil cultivation, so the quality and growth of flowers are strongly influenced by the physical and chemical properties of the culture medium in the pot. There are approximately three conditions that must be met by the culture medium. The soil should have the following three conditions: a moderate degree of solids content to provide physical strength, a high porosity to provide sufficient water and air retention, and a high CEC to retain nutrients. In addition, the material must be lightweight, inexpensive, and readily available.

　Usually, inorganic soil materials such as akadama soil and kanuma-soil are mixed with organic materials such as peat moss and humus. The former inorganic materials provide adequate solids content and porosity, while the latter organic materials provide light weight, high porosity, and CEC. Table 2 shows the physical and chemical properties of commonly used soil materials.

　Here, attention should be paid to the pH of peat moss. Peat moss is a very commonly used soil material because of its light weight and excellent physical properties. However, the pH of peat moss is as low as 3.5 to 4.5, which may cause the pH of the culture medium to drop depending on the mixing ratio. The pH should be checked when using peat moss.

Effective fertilizer application for potted flower cultivation

　Even if appropriate soil materials are combined, the culture medium itself does not contain any nutrients, so the nutrients necessary for growth must be supplied by fertilization. The key point is to consider the different growth phases of each potted flower and apply nitrogen fertilizer accordingly.

　The growth phases of potted flowers have already been summarized by Hosoya1) (Figure 1). According to this, the growth phases of potted flowers can be classified into the long-term flowering type (e.g. cyclamen), the developmental phase conversion type (e.g. poncetia), the nutrient growth type (e.g. ornamental plants), the dormant type after flower bud differentiation (e.g. hydrangea), and the utilization type of accumulated nutrients (e.g. orchids). Among these types, potted flowers that exhibit long-term flowering, developmental phase transition, and nutrient growth types require a continuous nitrogen supply throughout their growth, regardless of the amount of fertilizer applied, depending on the type and the length of the growth period. On the other hand, for the dormant type after flower bud differentiation and the type that uses stored nutrients, it is necessary to consider a nitrogen supply that has a high nitrogen requirement in the early stage of growth but not so much after the flower bud differentiation and flowering periods.

　Thus, in the cultivation of potted flowers, any fertilizer can be selected as long as the nitrogen supply can be matched to the growth phase, but liquid fertilizers are currently the mainstream. This is because the required amount of fertilizer can be applied to the pot at the required time, whether as a primary or a secondary fertilizer, at the same time as irrigation, allowing precise application while checking the growth phase.
　However, for potted flowers such as cyclamen, which require continuous absorption of nutrients during the growing season, the use of liquid fertilizers for all fertilizer application is recognized as a management problem, as it increases the frequency of fertilizer application and leads to higher costs. For this reason, the use of slow-release fertilizers is being promoted to save labor.

Types and characteristics of slow-release fertilizers

　The slow-release fertilizers mainly used for labor-saving purposes in potted flower cultivation are our brand names: Long, a coated compound fertilizer, and IB Nitrogen, a slow-release nitrogenous fertilizer.
　Long is a coated fertilizer made by coating potassium phosphonitrite with polyolefin resin as a seed component, and is available in a variety of grades, including compound fertilizers with different ratios of nitrogen, phosphoric acid, and potassium, and those containing trace elements. When long is applied to the soil, water vapor penetrates into the coating, and phosphorus nitrate and potassium gradually leach out as an aqueous solution to produce the fertilizing effect (Figure 2).

　For this reason, it is important to mix it with soil to obtain a long and stable nitrogen fertilizing effect, and it is used exclusively as a primary fertilizer at the time of potting up or repotting. Nitrogen-leaching types are roughly classified into linear and sigmoidal types, and various brands are available with nitrogen-leaching periods ranging from 40 to 360 days. Currently, the long type has been converted to the Ecolong series, which has a coated film with enhanced photodisintegration properties.

　On the other hand, IB nitrogen is an organic compound consisting of urea bound to isobutyraldehyde, with a nitrogen content of 31%. The urea is gradually released through hydrolysis reaction, and the nitrogen fertilizing effect is expressed through the transformation of ammonia-form nitrogen to nitrate-form nitrogen (Figure 3). IB nitrogen is usually mixed with phosphoric acid and potassium and sold as IB Kasei (product name: IBS1), which is granulated to about 5 to 10 mm in size. IBS1 is often used as a fertilizer for flowers and vegetables, responding to growers' questions such as "How many grains should I apply per pot?
The following is a summary of the results of the survey.

Cultivation of potted flowers using slow-release fertilizers

　As mentioned above, slow-release fertilizers have been introduced to save labor, and several examples using long and IB chemical fertilizers are presented below.

　Cyclamen are the most frequently used potted flower. For example, in Gifu Prefecture, a combination system of long and liquid fertilizer is used in bottom-feeding cyclamen cultivation in a downspout using a string, with a linear long 424-140 type (2 g/5 pots) as the primary fertilizer and 150 ppm N liquid fertilizer added as necessary2) . In Tochigi Prefecture, a system of combining a sigmoidal long type 424-70 type fertilizer (1 g/5 pots) in April and a linear long type 424-70 type fertilizer (4 g/5 pots) in September, with additional liquid fertilizer as necessary according to nutritional diagnosis3) , and in Mie Prefecture, a system of combining a sigmoidal long type 424-70 type fertilizer (1 g/5 pots) in the bottom-feeding of mats (1 g/5 pots) with liquid fertilizer as needed. In Mie Prefecture, water is supplied from the bottom of a flume using a string.
The production of standardized products is reported to be possible by using a fertilizer system4) in which all fertilizer is applied at a rate of 7.5-10 g/pot (No. 5) with Long 424-180 type fertilizer. Although there are various long fertilization systems, they are all consistent in their ability to supply nutrients according to the growth phase. It is necessary to select the most suitable fertilizer system in consideration of the cyclamen variety, the cropping pattern, the type of culture medium, and the management aspects.

　Poncetia is a potted flower of the developmental phase-shifting type that requires a relatively high amount of fertilizer. As shown in Figure 4, in a bottom-watering cultivation in Tochigi Prefecture, the quality of poncezias was equivalent to that of conventional cultivation using mainly liquid fertilizer by applying Super Long 424-100 type 10 g/5 pots at planting time in early August, and the amount of fertilizer applied was reduced by up to 20% compared to conventional cultivation5) . The amount of fertilizer applied can be reduced by up to 20% compared to conventional cultivation5) .

　On the other hand, IBS1, an IB compound, is a compound fertilizer used not only for flowers but also for vegetables and other potted plants in general, but it is rarely applied alone in potted flower cultivation and is often used in combination with liquid fertilizer or long-acting fertilizer. In the case of a single application of IBS1, it was found that when IBS1 was applied at 8 g/pot in a No. 4 pot to cultivate potted daisies that bloomed in late November, the quality was equivalent to that of conventional fertilization using mainly organic fertilizers6) .

Summary

　Potted flowers are plants for indoor enjoyment of their flowers and foliage in pots filled with culture medium, and the nature of the culture medium and fertilization strongly affect their growth and quality.
　The desirable conditions of culture soil are adequate hardness, water retention and aeration, and high fertilizer retention. Usually, peat moss and humus are selected as organic soil materials, and red ball soil and kanuma-soil are selected as inorganic soil materials, and culture soils with properties suitable for the growth of each species are prepared and used.

　Liquid fertilizers are widely used because of their ease of use. However, slow-release fertilizers have been attracting attention from growers who want to reduce the number of fertilizer applications and lightening the workload for fertilizer addition, and labor-saving fertilizer application techniques have been developed, such as total fertilizer application using a coated composite fertilizer long and placement of large-grain IBS1.
　In order to promote the use of slow-release fertilizers in potted flower cultivation, it is necessary to understand the in-pot environment, which is affected by the nature of the culture medium, to clarify the effect of slow-release fertilizers on nitrogen fertilization, and to expand the fertilization standards that are currently set only for a limited number of crops to other crops.

References

(1) T. Hosoya, Nutritional physiology and fertilization of flowering plants, Noubunkyo, 1995.
(2) M. Sumii, Utilization of long fertilizers in bottom-feeding cultivation of cyclamen, Agriculture and Science, December, 1989.
3) T. Takahashi, Fertilization management technology for cyclamen using fertilizer with controlled fertilizer effect, Research results of Tochigi Prefectural Agricultural Experiment Station
　Fruit Collection 24, 2005.
4) Etsuzo Nishida, Nao Nakano and Masayuki Kamada, Studies on fertilizer application in bottom-feeding cyclamen cultivation.
　Mie Prefectural Agricultural Technology Center Research Report 22, 1994.
5) Asuka Sakamoto, Nutrient absorption of poinsettia and labor-saving fertilization management technology using fertilizer with controlled fertilizer effect, Agriculture
　and Science 3, April, 2010.
(6) T. Hosoya, Hachigiku, Compendium of Agricultural Technology, Soil Fertilization Edition, Noubunkyo, 1998.

　

General Index of Previous Editions of this Journal in 2020

<January issue
Toward the §2022 era
　　　　　　　　　Yoshiaki Ando, General Manager, Administration Division, Jcam Agri Co.
§In the Kagoshima Island Region
　　Actual physical and chemical properties of sugarcane cultivated soils
　　　　　　　　　Kagoshima Agricultural Development Center Toshiyuki Mochida
§ Earl's melon string cultivation
　Total basal fertilizer and water uptake and absorption patterns of fertilizer with regulated fertilizer
　　　　　　　　　Former Faculty of Agriculture, Okayama University Masaji Masuda Fumikazu Yamaoka
<February/March combined issue
§Japan Soil Inventory (e-Soil Map II)
　　Dissemination of soil information aimed at by
　　　　　　　　　Research Center for Agricultural Environmental Change, National Institute of Agro-Environmental Sciences
　　　　　　　　　Soil Resource Assessment Unit, Environmental Information Technology Research Field Yusuke Takada
§Fertilizer with regulated fertilizer in three major soils in Okinawa Prefecture.
　　Labor-saving fertilizer application for spring planting of okra using
　　　　　　　Senior Researcher, Nago Branch, Agricultural Research Center, Department of Agriculture, Forestry and Fisheries, Okinawa Prefecture Hiroki Tanaka
<April issue
§ Achieve high quality and stable production of hard wheat
　　　Development of labor-saving fertilization technology
　　　　　　　　　Research Scientist, Agricultural Research Division, Mie Prefectural Agricultural Research Institute
(Currently Senior Manager, Suzuka Extension Division, Yokkaichi Suzuka Regional Agricultural Improvement and Extension Center, Yokkaichi Agriculture and Forestry Office)
§Seedling boxes and pooled seedlings go hand in hand.
　　　　　　　　　Masao Ueno, Technical Advisor, Tohoku Branch, Jcam Agri Co.
<May issue
§Traditional vegetables of Yamagata and Miyagi (various kinds of taro)
　　　Soil survey in the production area
　　　　　　　　　Hideyuki Saito, School of Food Science and Industry, Miyagi University
§ Fertilizers and nutrients:
　Coated phosphorus ammonium nitrate (long, high control, and
　(Nutricote) characteristics (Part 1)
　　　　　　　　　Masaru Shibata Shibata Professional Engineers Office
<June issue
§ Fertilizers and nutrients:
　Coated phosphorus ammonium nitrate (long, high control, and
　(Nutricote) characteristics (Part 2)
　　　　　　　　　Masaru Shibata Shibata Professional Engineers Office
§ Soil and fertilizer management to improve soil fertility in tea plantation soils
　　　　　　　　　Noriaki Gunshi Kake Noriaki, Kyushu Branch, JCM Agri Co.
<July issue
§ Fertilizers and nutrients:
　Coated phosphorus ammonium nitrate (long, high control, and
　(Nutricote) characteristics (Part 3)
　　　　　　　　　Masaru Shibata Shibata Professional Engineers Office
§ Utilization of Soil Data in Aichi Prefecture
　　　　　　　　　Aichi Prefectural Agricultural Experiment Station Katsutoshi Taki
.
§ Slow-release fertilizer at sowing in dense seedlingⓇ.
Effects of the application of "Microlong Total 280-100
　　　　　　　　　Toshiaki Tsuji, Director, Watashima Agricultural Extension Center
§ Points to keep in mind for soil fertilizer management in Global GAP
　　　　　　　　　Hideyuki Saito, School of Food Science and Industry, Miyagi University
<Oct.
§Next generation using ICT technology
　　　Building high-yield technology for staple rice
　　　　　　　　　Farm Frontier Inc.
　　　　　　　　　Visiting Professor, Faculty of Agriculture, Yamagata University
§ In continuous-row cultivation of open-air vegetables
　　　Trial of labor-saving technology using whole cell seedling basal fertilizer
　　　　　　　　　Kagoshima Agricultural Development Center
　　　　　　　　　Production Environment Department Soil Environment Laboratory May Kajiya
<Nov.
§ Establishment of a one-shot application method for passion fruit basal fertilizer
　　　　　　　　　Gifu Prefectural Agricultural Technology Center Tetsuya Suzuki
§Labor saving in promotion cultivation of eggplant by total basal application of fertilizer
　　　　　　　　　Fukuoka Prefectural Agriculture and Forestry Experiment Station Shigeki Morita
<Dec.
§Municipal waste molten slag as fertilizer and application development
　　　　　　　　　Shizuoka University, Faculty of Agriculture
　　　　　　　　　Associate Professor Department of Applied Life Sciences
§ In the cultivation of potted flowering plants
　　　Labor-saving fertilization with slow-release fertilizers
　　　　　　　　　Noriaki Gunshi Kake Noriaki, Kyushu Branch, JCM Agri Co.
§2020 General Table of Contents of Previous Issues of this Journal