Agriculture and Science 2021/7

J-Coat" coated fertilizer on paddy rice
　　　　Effects of total base fertilizer application and film collapsibility

Agriculture and Forestry Department, Kita-Akita Regional Development Bureau, Akita Prefecture
　Hideki Matsuda
(Former affiliation: Akita Prefectural Agricultural Experiment Station)

Introduction

　Coated fertilizers are fertilizers coated with resin or sulfur, such as urea, and are used in the production of many crops as functional fertilizers that can control nitrogen leaching, supply nutrients in accordance with crop growth, improve the utilization rate of fertilizer components, and save labor by reducing the number of fertilizer applications1) . On the other hand, the film of coated fertilizers is not always the same. On the other hand, although the film of coated fertilizers is biodegradable and photodegradable in the natural environment, it takes time for all the film to decompose, and there is concern that the remaining film will runoff into the water system with the rice paddy water after the fertilizer components are leached out. Therefore, in addition to reminding growers to prevent the outflow of the film, it is necessary to further develop technologies to improve the degradability of the film in the natural environment and to reduce the amount of resin used2) .

　Against this background, "J-Coat," a coated fertilizer with high film collapsibility, has been newly developed in recent years, which is expected to contribute to the suppression of outflow of the film from the system. In this study, the nitrogen leaching pattern of "J-Coat" was investigated in 2019 and 2020.
The effects of the paddy rice plant on the growth and yield of rice, and the rate of film collapse after one crop of paddy rice were clarified.

2. Methods

　The test was conducted in a rice paddy field (soil conditions: Gurei lowland soil (Hatano synthesis)) at the Akita Prefectural Agricultural Experiment Station (Owa Aikawa, Akita City, Akita Prefecture, Japan). The test variety was "Akita Komachi". The fertilizer used in the rice cultivation trials was a granular compound fertilizer containing J-Coat L70 and LP-Coat 70 (Table 1). 10 kg N/10a was applied to all layers on May 6 before plowing in 2019 and on May 11 after plowing and before tillage in 2020. Planting density was 21.3 plants/m2 in 2019 and 22.3 plants/m2 in 2020. The tillage summary is shown in Table 2.

　Nitrogen leaching rates were determined by placing a non-woven cloth containing 1 g of the fertilizer stock at rest on the ground surface of the field on the day of fertilizer application and burying it at a depth of 5 cm below the surface of the field (5 rows in 2019 and 3 rows in 2020) except during tillage, tillage and transplanting.
　The soil temperature in the field was measured at 5-cm depths at 1-hour intervals from fertilizer application to harvesting with a temperature recorder (product name: Ondotori-TR-71wf model, manufactured by T&D Co.

　The film collapse rate of the coated fertilizers was investigated using the JCAM method, in which mesh bags containing 100 g of the fertilizer (J-Coat L70 and LP-Coat 70) in 2019 and 50 g in 2020 were buried 5 cm below the rice surface in a row of three, then dug out about 6 months and 11 months after one rice crop, washed and dried, and then evaluated by applying external pressure to the test fertilizer. After washing and drying, the film collapse rate was evaluated by applying external pressure to the test sample fertilizer. The external pressure here was assumed to be the pressure applied at the time of plowing in the year following fertilizer application.

3. results

　The speed of nitrogen elution of J Coat L70 tended to be slower than that of LP Coat 70 in both years. Nitrogen leaching rates above 801 TP3T occurred in early July for LP Coat 70 in both years, while for J Coat L70 it was mid-July in 2019 and late July in 2020 (Figure 1). The timing of the leaching rate of 801 TP3T, which is estimated based on the average daily soil temperature in the field (when the average daily soil temperature reached an integrated temperature of 1,750°C), was late July in 2019 and early August in 2020 for both test fertilizers, indicating an early trend of nitrogen leaching in both years (Figure 2).

　Comparing J- and LP-coated areas for nitrogen uptake by paddy rice, the J-coated area remained lower in 2019 and the same in 2020 (Figure 1); growth in the J-coated area remained lower in stem number from June onward than in the LP-coated area in 2019, and leaf color was lower in 2020 (Figure 3 ). This was likely due to the slower rate of nitrogen leaching of J-coat L70 than LP-coat. Comparison of yield, yield components, and brown rice quality between the J- and LP-coated treatments showed no statistically significant differences between the two years (Table 3).

　Although the film collapsibility of the test fertilizers after one crop of paddy rice was not clear in appearance (Figure 4), the JCAM method, which evaluates the film by applying external pressure to the film, showed that the film did not collapse after one crop of paddy rice in the LP coat, whereas about 40% of the J coat did (Table 4).

Summary

　The effect of full basal application of J-Coat, a newly developed coated fertilizer with an easily collapsible film, on paddy rice plants and its film collapsibility were investigated. The results showed that nitrogen release of J-Coat L70 tended to be slower than that of LP-Coat 70, but the yields were similar. The film collapse rate after one crop of paddy rice was higher than that of LP Coat, indicating that J-Coat L70 contributes to preventing the film from leaching out of the system.

　However, the results of this study were obtained when all layers were applied in the middle of May. In Akita Prefecture, side-row application of fertilizer at the time of transplanting is widely used, and it is assumed that the timing of application may be in late May. In addition, although the film collapse rate of J-coat was higher than that of LP-coat, it was about 40% after one crop of paddy rice. Further studies on the relationship between the burial period and the film collapse rate, and on the amount of film loss on a field scale, are needed to control the outflow of the film from the system.

References

(1) Ueno, M.; Ueno, M.; Ueno, M.; Ueno, M.; Ueno, M. Practical Extension Technology Using Fertilizer with Controlled Fertilizer Effect (Coated Fertilizer). Agriculture and Science. p.6-11
　(2017)
(2) Japan Fertilizer and Ammonia Association, National Compound Fertilizer Manufacturers Association. The Fertilizer Industry's Response to Marine-Drifted Plastics................
　About the Oyeon (2019)

Soil and flower - 3rd
　Conditions for Good Soil Physical Properties - Part 2
　How is soil hardness determined?

Hokkaido Branch Office, JCM Agri Co.
　Teruo Matsunaka Technical Advisor

　Last month, we discussed soil thickness in terms of "soil thickness and hardness," one of the four conditions for good soil for crop production, which is related to the physical properties of soil. This month, we will focus on soil hardness.

1. what determines soil hardness

　Some soil is so hard that it cannot be dug with a shovel, while others can be dug with ease.
What determines soil hardness? Basically, the size of "soil grains" (called grain size) determines soil hardness. Grains of soil? Some people may wonder why soil is hard. But think of sand and clay. Sand is rough and you can see each grain with your eyes. However, clay grains cannot be seen with the eyes and can only be seen in clumps.

　When the organic matter contained in the soil is completely removed and only the soil particles are left, the soil is composed of three types of particles: sand (classified into two types: coarse sand and fine sand), clay (clay here does not refer to clay used for clay works but to the very fine soil particles shown in Figure 1), and silt (fine sand), which is intermediate in size between the two. The problem is how much proportion these three types of particles have. The question is what proportion of these three types of particles make up the soil.

2. the finer the soil grains, the harder the soil.

　If a glass bead is packed in a certain container, the smaller the bead is, the more space it has. If the glass beads are large, they cannot be packed without gaps, and many spaces are created. The term "denseness" is used to describe how many particles are packed in a certain volume. The degree of density becomes larger when it is packed with a small glass ball than when it is packed with a large glass ball. Clay has the finest grains, so clayey soil has a high degree of density. On the other hand, sand has coarse grains, so sandy soil has a small degree of density. Therefore, clayey soil is tightly packed into a certain volume and becomes hard soil. Sandy soil with coarse particles does not often produce soil as hard as clayey soil.

3. how is soil grain size determined?

　Then, how is the size of soil grains determined? If soil grain size is innately determined, there would be no difference between sticky soil and sandy soil. Soil grain size is related to the way soil is formed.
　The raw material of soil is basically rock (parent rock) (with the exception of black earth, which is derived from volcanic ash). The rock is broken into small pieces by weathering. The finely crushed rock is called the parent material of soil. The size of the particles that make up the soil is determined by the quality of the rocks used as raw material and the degree of weathering. If the soil has been exposed to weathering for a long time or if the rock is brittle and susceptible to weathering, the soil will have more fine particles, such as clay and silt. This results in fine-grained soil. The opposite is sandy (coarse-grained) soil. The intermediate state between the two is medium-grained soil.

4. very long time is needed to change the hardness of the soil

　The hardness of soil is due to the finer and denser particles of soil. The soil particles contain the time it took for the rocks to break up and for the soil to be formed by the action of living organisms. Thus, it takes a daunting, very long-term effort to essentially soften the hardness of the soil.

　For example, by feeding coarse organic matter, such as compost, to the soil over many generations, a cushion of organic matter is created in the soil, which gradually softens the soil. In addition, one might think that mixing in sand or other materials would be a good idea. Of course, this is theoretically possible. It may be possible in a small area such as a home garden. However, in a large field, sand must be nearby in large quantities. Sand from the coast is not suitable because of its salinity. It must be river sand. Considering these factors, bringing sand into a fine-grained soil is a picture-perfect and unrealistic idea. It is impossible to change clayey soil into sandy soil.

5. soil hardness is not determined by soil particles alone

　So far, for the sake of simplicity, I have explained soil hardness only in terms of soil particles. However, soil hardness is not that simple. For example, soil hardness varies depending on the moisture content in the same soil. This can be seen from the fact that clay soil becomes hard and hard when it is dried. If such soil is gradually moistened with water, it becomes softer and softer, and finally liquefies into a sludge, which is outside the concept of hardness.
　The nature of soil hardness is very complex, even when we speak of soil hardness in a nutshell. Here we are simplifying the story.

6. hardness is not the only thing that affects root elongation

　Last month and this month we discussed the issue of soil thickness and hardness. This is because we wanted to consider the thickness of the effective soil layer in which roots can grow. However, whether the roots can grow or not is not only determined by the hardness of the soil. There are three factors that inhibit the growth of crop roots. (1) mechanical resistance derived from soil hardness, (2) soil aeration, which indicates whether sufficient air is being pumped into the soil so that root respiration is not adversely affected, and (3) soil moisture conditions. These factors are not independent of each other, but are interrelated, making them even more complex.

7. Hardness is not an inhibiting factor in general soil

　Figure 2 shows the results of an experiment examining the relationship between the above three factors and root elongation. The volumetric weight of 1.0 in Figure 2 indicates that 1 cm3 contains 1 g of dry soil, which is a very normal value for ordinary soil. The increase in volumetric weight can be thought of as the soil particles becoming finer and more cohesive.

　Therefore, according to Figure 2, when the soil is wet enough to form puddles, the gaps in the soil are filled with water and the soil lacks oxygen (poor aeration). Therefore, regardless of the volumetric weight of the soil, peas cannot fully extend their roots due to lack of oxygen.
　When there is no puddle and the soil contains some water, mechanical resistance, i.e., soil stiffness, will now inhibit root growth. However, this is the case for slightly fine-grained (clayey) soil with a volume weight of more than 1.1. Ordinary soil with a volume weight of up to 1.0 has water and air in the spaces between the soil, so it is in optimum condition for root growth.

　When the soil becomes dry, mechanical resistance due to hardness inhibits root elongation in soils with large volumetric weights (fine-grained and clayey). However, in a typical soil with a volume weight of 1.0, mechanical resistance due to hardness does not inhibit root elongation. And, of course, in a soil so dry that the crop wilts, lack of water inhibits root elongation regardless of the volume weight.
　In other words, it is concluded that soil hardness is a problem in fine-grained soil (clayey soil), and that in general soil hardness itself should not be considered to be an impediment to root growth. For soils with low volumetric weight and light weight, such as black granite soil (soil derived from volcanic ash), soil hardness is hardly a problem. In fact, because of its lightness, black soil is susceptible to wind erosion (soil being blown away by the wind).