Agriculture and Science 2023/4

Under Climate Variable Conditions
　　Consideration of the usefulness of "seedling box leave" for paddy rice

Farm Frontier Inc.
　Hiroshi Fujii Chairman of the Board

Introduction

　In 2022, the weather conditions in Sakata City, Yamagata Prefecture, were characterized by poor weather conditions from July to September due to the continuous lack of sunshine (60% of the normal) from August 1.5 to September 1.5 (Fig. 1).

　In the past 32 years from 1991 to 2022, the lowest total hours of sunshine from the first half of August to the first half of September was 114 hours (50 hours less than the normal) in 2003 (cold damage), when the crop index was 94, and the second lowest was in 2022 (cold damage), when the crop index was 94 (50 hours less than the normal).
The least number of hours of sunshine was 137 hours (60% of the normal) in 2022, which was also a significant shortage of sunshine in that year. Compared to previous years in the Shonai area of Yamagata Prefecture, where the crop condition index was below 99 (below normal) due to lack of sunshine, the 2022 crop year had fewer sunshine hours than the 1995 crop year with a crop condition index of 92 (173 hours, 76 hours below normal) and the 1998 crop year with a crop condition index of 98 (159 hours, 70 hours below normal).

　Next, looking at the weather conditions (average temperature and accumulated sunshine hours) in August, the rice ripening period, nationwide (Table 1), the regions with average August temperatures similar to the normal year but significantly less accumulated sunshine hours than the normal year, regions with average sunshine hours similar to the normal year but average temperatures higher than the normal year exceeding 27°C, which is a concern for quality deterioration, and regions with less accumulated sunshine hours than the normal year but average temperatures above 27°C, which is a concern for quality deterioration. In all of these areas, there are concerns about yield loss and quality decline due to lack of sunlight and high temperatures during the ripening period.

　With the normalization of rice crop growth under conditions of lack of sunlight and high temperatures in the future, the improvement of paddy rice productivity is particularly important from the viewpoint of food security. Therefore, this paper describes from the viewpoint of photosynthetic capacity (source capacity), which is involved in improving rice productivity, and proposes the usefulness of coated fertilizers such as "seedling box leave" and strategies to further improve productivity.

2. evaluation of the rice side

　If there are any relevant items in the evaluation of the rice crop for the current year from the source side (the side that produces and supplies photosynthetic products) and the sink side (the side that accepts photosynthetic products), the viewpoints will be used as improvement measures for the next year's rice crop.

(1) Evaluation of the source side (the side that produces and supplies photosynthetic products)

0■Lower-than-normal leaf color at ear emergence
　Low leaf color at ear emergence means low nitrogen per unit leaf area, which is disadvantageous for photosynthesis under sunlight deficit conditions. If the upper leaves are nitrogen-deficient (i.e., low water uptake capacity due to insufficient nitrogen supply from the paddy field or low root vigor), nitrogen translocation from the lower leaves will compensate for the nitrogen deficiency in the upper leaves, resulting in a progressive decrease in leaf color in the lower leaves.

0■Reduction of paddy field progressed, ■Activation was delayed and early growth was suppressed.
　When the reduction of the paddy field progresses, delayed transplanting and suppression of initial growth (partial moetting) result in fewer roots, and the number of roots is reduced, and the number of roots is also reduced under the condition that the paddy field is not dried out at the right time due to continuous warm water management (shallow water) to compensate for the suppression of initial growth. This reduces the amount of roots involved in the absorption of nutrients during the ripening period, which is also a factor that suppresses ripening under conditions of insufficient sunlight and high temperatures.

z■ Fields where siliceous materials have not been applied, ■ Fields with low silicon supply
　When siliceous materials were not applied and silicon supply was low, the specific leaf weight (thick leaf blade), which plays a role in photosynthetic capacity, was not sufficient to ensure a good light-receiving posture by improving leaf blade erectness, which may also be a factor in reduced photosynthetic output under conditions of insufficient sunlight.

(2) Evaluation of sink side (side that accepts photosynthetic products)

　There are two types of evaluation on the sink side: quantitative and qualitative. Quantitative evaluation is based on the number of branches per square meter佅, while qualitative evaluation is based on the number of secondary branches that are unfavorable to ripening.

0■1 m2佅 number is greater than the 1 m2佅 number of the indicator shown for each variety.
　　When the number of 佅 per square meter is high, the number of distribution sites for photosynthetic products increases, so ripening is disadvantageous under conditions of insufficient sunlight and high temperatures.

0■Increased number of ears per square meter due to suppression of early growth and increased number of ears per square meter
　When early growth is suppressed and the number of ears per square meter is low and the number of ears per square meter is high, the number of secondary branches, which is unfavorable to ripening, increases, which is unfavorable to ripening (the number of ears per ear is positively correlated with the number of secondary branches).

0The balance between the number of ears per square meter and the number of ears per square meter (secondary branches伷佅 number) that make up the 1 m2佅 number is important, and under variable weather conditions, it is important to ensure early growth and to obtain the required number of ears as early as possible.

3. characteristics of factors involved in photosynthesis under conditions of lack of sunlight and high temperature

　Factors on the leaf blade side that affect photosynthesis, which indicates source capacity, include

(i)Photosynthetic capacity of single leavesis the leaf bladeNitrogen concentration(per leaf area)Nitrogen contentand a positive correlation with leaf
　The amount of nitrogen per area isLeaf thickness(specific leaf weight), and the thicker the leaves are, the more leaf area per
　The amount of nitrogen in the soil is increased.silicic acidhas the effect of increasing specific leaf weight.

(2) Photosynthesis rate of leavesaging(carbon dioxide fixation system senescence), which affects leaf senescence.
　Factors.Nitrogen absorption(Fertilizer nitrogen has the effect of reducing leaf senescence.)cytokinin(synthesized in the root and
　(a hormone that is translocated to the leaves), andRoot FunctionsKeeping the "+" level high inhibits leaf senescence.

(iii)Amount of photosynthesis in the communityTo improve theerectnessThe root cause is the improvement of light-receiving conditions by improving the
　This increases the amount of light received and maintains photosynthesis in the lower leaves, which provide nutrients to thesilicic acidplays an important role
　The company is fulfilling its

To maintain the source capacity, theSustained nitrogen supply (fertilizer application, soil fertility)andsilicic acidPhotocoupling of lower leaves by
　It is important to maintain maturity (suppression of senescence) and dry matter production even under conditions of lack of sunlight and high temperatures.

　Root-side factors that play an important role in photosynthesis include

(1) For high yields, high physiological activity of the root system during the ripening period and a slow decline in
　Root agingdelaying the 佅 will lead to improved ripening (especially in the secondary branches伷佅).

(2) Since the availability of an active root mass determines photosynthesis during the ripening period, it is important to ensure that the root mass is high enough to maintain the photosynthesis rate during the ripening period.taproot(medium dry), (medium dry), (medium dry)outer root(at intervals of) two or more
　Appropriate water management to promote the formation of (irrigation) and other factors and to ensure early growth are important.

(iii) Leaf blade aging is slow and leaf color can be maintained for a long period of time, i.e., leaf color can be maintained for a long period of time, i.e., leaf color can be maintained for a long period of time.
　The total amount of itokinin is high.lower leaves withering awayis slow, so theLeaf color of upper leavesis maintained, resulting in
　Photosynthesis is maintained, resulting in good ripening and higher yields.

(4) If the ability to absorb nitrogen is reduced during the ripening period and the leaf blade is deficient in nitrogen nutrition, theUpper nitrogen in lower leaves
　Translocation to the leavesThis will cause a decrease in leaf color in the lower leaves, and alsoRoot Vitality(water absorption capacity) decreases.

　The nutrients especially needed to improve photosynthetic capacity of rice plants under low sunlight and high temperature conditions are (1) nitrogen (nitrogen content in single leaves, suppression of leaf senescence by continuous small nitrogen supply, and maintenance of root vitality by continuous supply of photosynthate products from lower leaves to roots) and (2) silicon (improvement of leaf blade specific leaf weight, better photosensitive condition, and root oxidative capacity of roots), which are truly the two wheels of the wheel. In addition, the roots that support photosynthesis of the leaf blade are important (there are "nadir roots" that extend deep into the paddy soil and "epiphytic roots" that expand and extend in the surface layer of the soil, each of which plays an important role during the ripening period).

　Furthermore, even if the production of photosynthates is increased by improving the interaction between leaf blade and root, the distribution destination 佅(sink) capacity is important, and the formation of a 1 m2佅 number that allows proper distribution of the produced photosynthates and the number of 1 m2 ears that make up this number and the 1 ear The balance between the number of ears per square meter and the number of ears per square meter (so that the number of ears per square meter is not excessive) is important.

　In years with fewer hours of sunlight, silicon and nitrogen uptake by paddy rice tends to be lower and yields decrease regardless of the silicon supply from the soil (Figure 2).

In order to improve photosynthetic capacity, it is necessary to increase the amount of nitrogen and silicate absorbed, and in years with insufficient sunlight, the amount of silicate supplied from the soil may not be sufficient.
Sustained supply of small amounts of nitrogen from near the zone is an important technique to maintain nitrogen nutrition of rice plants.

　Apparent photosynthetic rates were measured under different photon conditions of 2000 (sunny), 1000 (lightly cloudy), and 500 (cloudy) for the no-silica and silica (Silica 200) treatments (Table 2).

　The rate of photosynthesis of the leaf blade tended to be higher in the high-silica zone than in the low-silica zone, regardless of light conditions. The photosynthetic rate in the silicate-applied zone was 121 on sunny days, 124 on lightly cloudy days, and 129 on cloudy days when the rate in the no-silicate-applied zone was 100, indicating the effect of silicate application. This may be due to the higher amount of nitrogen per unit leaf area in the silicon-applied area due to the increase in SLW (specific leaf weight), which also suggests that silicon is highly effective as a countermeasure under conditions of insufficient sunlight.

4. what is the strongest all-weather system (Figure 3)

(1) The response of paddy rice to

(1) Soil reduction through soil preparation (steel slag) and rice straw rot promotion (pinpoint application of enzyme materials)
　The number of stems required at an early stage is achieved by mitigation, side-row fertilizer application, and a dash start by leaving the seedlings in the box (drip effect).
　It can be secured (No. 3 division: subordinate division).

(2) Growth adjustment (deep watering and drying in the middle) can be carried out at the right time to secure heavy stems (thick stems) with a dry matter weight of 1 stem, and
　This will ensure sufficient "nadir roots" and "upper roots."

The effect of efficient soil preparation (silicic acid) and the "leave it to the seedling box" method of applying fertilizer in close proximity to the surface roots of paddy rice seedlings are also important for the development of rice seedlings.
　The continuous supply of small amounts of nitrogen to the roots of the plant in the late vegetative stage (suppression of late wilting, maintenance of nitrogen nutrition, and root vigor).
　The system will be secured to improve the quality of the system (i.e., to maintain its strength).

　However, the current rice paddy is vulnerable to weather disasters (high temperatures, lack of sunlight, etc.) due to poor early growth and root elongation, delays in securing the required number of stems, inadequate timing of growth adjustment such as drying out, resulting in suppressed root mass, and a lack of silicon due to stagnant soil preparation, combined with insufficient nitrogen supply in the latter half of growth, leading to reduced leaf color and withering of the lower leaves. This situation can be changed by the methods (1) to (3) above.

(2) Next-generation fertilizer application system Information-linked soil preparation + "side-row fertilization + leaving the fertilizer to the seedling box

　The following procedure of information-linked soil preparation + "side-row fertilizer application + leaving the seedling box" in the next-generation fertilizer application system will be implemented.

　The information-linked fertilizer application system determines the amount of nitrogen for fertilizer application based on the soil fertility of each field, target yield, and variety (whether or not the field has fallen over), etc., and the amount of nitrogen for side-row fertilizer application is determined based on the dry-soil effect information for each field in the current fiscal year. The amount of nitrogen for side-row fertilization is determined based on the dry-soil effect information for each field in the current year. This reduces fertilizer application and soil fertility costs while ensuring stable yields (high quality) even under variable weather conditions (lack of sunlight, high temperatures, etc.) (Photo 1).

concrete method
0Information-linked soil preparation
siliceous material
(1) Selection of siliceous materials to be applied: If the reduction risk of the field is assessed and there is a reduction risk, the silica and silicic acid materials should be selected.
　Select steelmaking slag that contains iron and manganese, which mitigate the reduction process, in addition to lime.
(2) Amount of siliceous material applied: Based on soil analysis (pH, CEC) and application history of siliceous materials, the amount of siliceous material applied was determined for each field.
　Variable application of siliceous materials leads to cost reduction.

reduction measure
(1) Selection of measures to be implemented: Evaluate the reduction risk of the field and select the measures to be implemented. Measures to be selected and
　These include drainage measures (subsoilers), promotion of rice straw maturation (enzyme materials, lime nitrogen), application of steel slag, and seedling cultivation.
　There is quality improvement, shallow planting, etc.
(2) Pinpoint application of rice straw rot accelerators: within and between fields by drone sensing and sketching.
　The areas with a high risk of reduction of C

Fertilizer application linked to 0 information
　By changing the amount of nitrogen applied to each field based on the evaluation of the field soil fertility (regional variation) and dry-soil effect (annual variation), which are factors that cause variation in the soil nitrogen absorbed by paddy rice, it is possible to reduce the variation in soil fertility from field to field. Specifically, the amount of nitrogen in side-row fertilizer (fast-acting N: equivalent to base fertilizer) is optimized based on information on soil fertility (regional variation) and dry-soil effect (Fig. 4), and variable fertilizer application is performed for each field (in fields with high dry-soil effect, the amount of nitrogen in "side-row fertilization" is reduced). Select and implement the optimized amount of nitrogen and fertilizer type (leaching type) of "seedling box application" (slow-release N: equivalent to additional fertilizer) for each field based on soil fertility, variety, yield target, and weather conditions.

Effects of "information-linked soil preparation" + "side-row fertilization + leaving the seedlings in the box
0Ensuring initial growth (Table 3)
(1) The number of stems per square meter and leaf color about one month after transplanting were compared between the "side-row fertilizer + seedling box-applied" and the farmer's customary treatments.
　In the "side-row fertilizer + seedling box-applied" zone, the target number of stems of about 300 stems per square meter was secured in all years.
　In the farmer-customary area, the weather conditions after transplanting (May 10 to June 10) were very favorable, and the leaf color remained high. In the farmer's conventional area, weather conditions after transplanting (May 10 to June 10)
　In 2021, when the temperature was high, and in 2022, when the temperature was low and sunlight was scarce (Table 4), there was a decrease in the number of stems and a decrease in leaf color.

　Even under severe post-planting weather conditions, theSide-row fertilizer application + seedling box leave-as-you-gois an issue in the field.
　The results showed that the new method was consistently effective in securing the initial growth of the plant in the early stages of the season.
　The use of drainage measures, the application of steel slag, and the pinpoint application of rice straw rot-promoting materials (enzyme materials) will help to reduce the amount of water used in the field.
　　In addition, the reduction measures to be taken by the company are alsoSide-row fertilizer application + seedling box leave-as-you-goStable initial growth coupled with nitrogen supply by
　　It was possible to secure growth.

Improvement of culm leaf fullness
0Maintaining high culm and leaf fullness until maturity without decreasing it after the ear-justification stage leads to improved ripening without decreasing photosynthesis. If nitrogen supply to the rice body is low after the ear setting stage, culm leaf fullness will decrease, leading to a decrease in yield.
0The establishment of a sustained small amount of nitrogen supply system after the earning stage of rice leads to the maintenance of photosynthetic capacity by the leaf blade under conditions of lack of sunlight and high temperatures that affect photosynthesis. From this point of view, theContinuous supply of small amounts of nitrogen through "leave it to the nursery box" or other meansIn addition, it is also important to manage fertilizer to secure root volume, which is the absorbing side of nutrients, and to maintain root vigor during the ripening period.

Leaf color at the time of maturity (Table 5)
Comparing the leaf color trends after ear emergence in the "side-row fertilizer + seedling box" and the control (farmer's practice), there was a significant decrease in leaf color in the third leaf from the top in the control. In the control, senescence pressure was observed in the lower leaves from 20 days after ear emergence, indicating a wilting pattern.
The results showed that the "side-row fertilization + leave it to the seedling box" method resulted in less wilting of the leaf blade, maintained the color of the third leaf from the top, increased root vigor (water absorption capacity), and was more resistant to weather fluctuations (lack of sunlight in 2022 and high temperatures in 2021).
The improvement of early growth by mitigation of zero reduction, the improvement of photosynthetic capacity by silicic acid, and the continuous supply of nitrogen by placing seedlings in the seedling box prevented the decline of leaf color even in the 2022 year of severe lack of sunlight.

Significance of continuous nitrogen supply during the ripening period by using "Seedling Box Leave" and other coated fertilizers.
The intensity of nitrogen uptake by leaf position is higher in the upper leaves, and when the amount of nitrogen supplied by the paddy soil (fertilizer nitrogen and soil nitrogen) is high, the intensity of nitrogen uptake in the upper leaves depends on the nitrogen in the soil and not on the translocated nitrogen from the lower leaves.

　On the other hand, when the amount of nitrogen supplied by the paddy soil (fertilizer nitrogen and soil nitrogen) is low, the uptake intensity of nitrogen in the upper leaves depends more on the translocated nitrogen from the lower leaves than on the nitrogen in the soil. In other words, the decrease in leaf color of lower leaves during the ripening period indicates a nitrogen deficiency in the upper leaves, and weather conditions unfavorable to photosynthesis, such as lack of sunlight and high temperature, further promote the decrease in leaf color of lower leaves, which, combined with the decrease in root vigor (decrease in photosynthetic product supply to roots due to decreased photosynthetic capacity caused by decreased leaf color in lower leaves), causes late wilting of the rice plant Late wilting of rice plants is occurring.

z The trend is that the number of rice plants as described above is increasing, and to break through this trend, it is important to have a fertilizer system that can sustainably supply the proper amount of nitrogen, and from this viewpoint, it is important to use a "fertilizer system that can sustainably supply the proper amount of nitrogen.Coated fertilizers, such as "Seedling Box Leave," are useful.The following is considered to be the case.

No.20 Protein and carbohydrates are trade-offs that affect the taste of agricultural products.

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

　In the previous issue, we introduced the GS-GOGAT system, in which plants absorb ammonium and nitrate ions, which are nitrogenous nutrient ions, and utilize carbohydrates produced by photosynthesis in leaves to produce amino acids, which are the raw materials for proteins. Using this system, plants supply themselves with all the amino acids necessary for protein synthesis. Proteins, along with carbohydrates, greatly affect the taste of agricultural products.
　In this article, we will consider the curious trade-off between protein and carbohydrate content in crops, which has a significant impact on the taste of agricultural products, from the perspective of the GS-GOGAT system.

1. what is a trade-off relationship?

　A trade-off is a relationship in which one factor increases while the other decreases, like a seesaw on a playground, and the two factors cannot both increase and be compatible. For example, as shown in Figure 1, when the nonstructural carbohydrate (NSC) content per panicle of rice is low, the protein content in brown rice is high, and when the NSC content is high, the protein content in brown rice is low, indicating that a trade-off relationship exists between the two.

2. why the trade-offs?

　The reason for the trade-off between protein and carbohydrate content in plants is that the carbohydrate content in plants (A) is determined by the difference between the amount of carbohydrate produced by photosynthesis (B) and the amount of carbohydrate consumed when the absorbed nitrogen is converted to protein in the body (C) (A = B -C).

　This can be well understood from the perspective of the GS-GOGAT system introduced in the previous issue. That is, plants that are given a lot of nitrogen from compost or chemical fertilizers absorb a lot of nitrogen, of course. When more nitrogen is absorbed, it is incorporated into the GS-GOGAT system and amino acid synthesis is activated, resulting in an increase in protein content.

　Recall that at this time, in addition to ammonium and nitrate ions absorbed from the roots, another raw material was needed for amino acid synthesis. That is 2-oxoglutaric acid. 2-Oxoglutaric acid is an organic acid that is an intermediate product of the decomposition process of photosynthetic carbohydrates produced in leaves by plant respiration. Therefore, in order to supply large amounts of this organic acid, the decomposition of carbohydrates must be increased through active respiration. As a result, the amount of carbohydrates remaining in the plant body is inevitably reduced.

　Conversely, if only a small amount of nitrogen is provided, plants synthesize only a few amino acids and have low protein content. Since not much is used for amino acid synthesis, not much is needed for the intermediate products of carbohydrate breakdown by respiration. As a result, more carbohydrates are left over, resulting in a relatively high carbohydrate content. This is the main mechanism that causes the trade-off relationship between protein and carbohydrates in plants.

Nitrogen fertilization and crop quality

　The trade-off between protein and carbohydrate content in crops means that nitrogen fertilization has a significant effect on the carbohydrate content of crops. We would like to consider this relationship in terms of the eating quality of rice and the relationship between different cultivation methods and the taste of the crop.

1) Protein content and eating quality of rice

　The overall eating quality rating of rice (milled rice) is clearly higher the lower the protein content (Figure 2).

　This is because the lower the protein content, the higher the carbohydrate (starch) content, resulting in a taste that the Japanese prefer. Therefore, nitrogen fertilizer management that does not unnecessarily increase the protein content of rice is required to improve the taste of rice. However, too low nitrogen application in pursuit of low protein content will result in lower brown rice yield. In other words, producing high starch, good-tasting rice requires a high level of technology to manage nitrogen fertilization in a way that strikes the right balance between taste and yield.

　However, the eating quality of rice (milled rice) is not only affected by protein content, but also by low amylose content, which constitutes the starch of rice. The amylose content of rice is more influenced by variety characteristics than by nitrogen fertilization. Therefore, good-tasting rice varieties are selected from breeding material that has characteristics that result in low amylose content in the rice.

(2) Differences in cultivation methods and the taste of agricultural products

　It is often pointed out that organically grown produce tastes better than conventionally grown produce (conventionally grown using chemical fertilizers and pesticides). Is this a general fact? This can also be explained in terms of the relationship with the amount of nitrogen applied.

　Compost is used as the nutrient source for the crop in organic farming, while chemical fertilizer is used in conventional farming. Let us now consider a case in which crops are grown using these two sources of nutrients with the same amount of total nitrogen applied. Even if the amount of total nitrogen applied is the same for both sources, the amount of nitrogen in a form that is easily absorbed and utilized by the crop (inorganic nitrogen) is usually much higher with chemical fertilizer than with compost. This is because the nitrogen in compost contains organic nitrogen that cannot be immediately absorbed by the crop.

　In other words, from the crop's point of view, the amount of inorganic nitrogen that can be absorbed immediately is greater with conventional chemical fertilizer than with organic compost, even though the total amount of nitrogen given is the same. Then, the nitrogen absorption of the crop is higher under conventional cultivation than under organic cultivation, resulting in a higher protein content and, consequently, a lower carbohydrate content. Since the taste of agricultural products is considered to increase with carbohydrate content, such as sugars and starches, the result is that organic produce is evaluated to be better tasting, even though the total nitrogen content fed is the same.

　However, this is not due to differences in cultivation methods, but mainly to differences in the amount of inorganic nitrogen contained in the nutrient sources used. If the amount of nitrogen applied from chemical fertilizers is equal to the amount of inorganic nitrogen contained in compost, the carbohydrate content of the crop, such as sugars, will not differ much between the two.

　In other words, the fact that organic produce generally has lower protein content and higher carbohydrate content than conventional produce is not due to differences in cultivation methods, but rather to differences in the amount of inorganic nitrogen applied, even when the total nitrogen content fed is the same.