Agriculture and Science 2023/12

本号の内容

§ Growth of Chinese cabbage and nitrogen application
Former Toyama Prefectural Agricultural Technology Center
松本　美枝子
§土のはなし－第27回農業と環境問題－その２
農地由来の窒素による水質汚濁
前 ジェイカムアグリ株式会社
北海道支店 技術顧問
松中　照夫
§2023 General Table of Previous Editions of this Journal

　

　

Growth of Chinese cabbage and nitrogen application

Former Toyama Prefectural Agricultural Technology Center
松本　美枝子

Introduction.

　The objective of vegetable cultivation technology is to ensure a stable and abundant harvest of high quality vegetables. Here, we examined fertilization and cultivation methods for Chinese cabbage, an autumn/winter vegetable.

　In the past, Chinese cabbage was generally sold as a single plant, and the problem was that it was heavy and large, but today, when selling in two to four portions has become the norm, large harvests of 2-3 kg/plant are common. As for the quality, the product value is
The problem was to avoid the occurrence of sesamosis, which significantly reduces the number of plants. Therefore, a fertilizer application method to avoid these problems was investigated. Here, an early maturing variety (60-day type) was used for the study.

Growth progress of Chinese cabbage

　The former synthesizes sugars and amino acids and translocates them near the stem apex (growth point), resulting in the enlargement of the tuber. Therefore, it is necessary to grow the outer leaves, which are photosynthetic organs, large enough in the early stage to maintain the photosynthetic function until harvest. In other words, the fertilizer application method should focus on basal fertilizer, but it is important to ensure that fertilizer does not run out until the time of harvest.

　In Figure 1, leaf position is shown as logarithmic, with the leaf that initiates tuberization as 1.

　Leaves at the beginning of differentiation gradually increase in size (immature leaves) and remain constant in size (mature leaves). Immature leaf
The inflection point is indicated by ↓. The tuberculate leaves rotate in a 3/5 phyllotaxis and gradually increase in size.

　If the plot of leaf weight deviates from the "straight line showing the relationship between leaf position and leaf weight (Figure 1)" for mature leaves, the nitrogen supply at the time of leaf maturity is insufficient, and if it deviates above the straight line, the nitrogen supply was excessive. If these changes in leaf weight are observed, the amount and timing of basal and supplemental fertilizer should be adjusted.

　Next, the logarithmic representation of leaf position was removed, and the leaf weights and degree of sesamosis occurrence at 30, 45, and 60 days after planting are shown in Figure 2. The same sample was also divided into main veins and leaf blades, and their respective nitrate nitrogen concentrations are shown in Figure 3 (Supplementary Data 1).

　Here, sesamoidosis newly occurring on immature leaves was defined as a type 1 outbreak, while sesamoidosis with reemerging outbreaks on mature leaves was defined as a type 2 outbreak.
　In Figures 2 and 3, leaf position is indicated as an integer. In Figures 2 and 3, the relationship between leaf position and leaf weight is shown as an inflection point ↓, as in Figure 1, because differences were observed in the relationship between mature and immature leaves.
　Leaf weight and degree of sesamosis incidence were examined on two plants each at 30, 45, and 60 days after planting (Figure 2). At 60 days after planting, the incidence of sesamosis increased significantly at leaf positions 25 to 45 (type 2). This type 2 sesamosis occurred at the inner leaf level below the inflection point.

　In Figure 3, nitrate nitrogen concentrations in the main veins and leaf blades were investigated using the material in Figure 2. In all the sections, the concentration in the main vein was higher than that in the leaf blade, and a concentration peak was observed in the main vein about 10 leaves inside from the inflection point, which almost coincided with the initiation site of type 1 development. It was thought that nitrate-nitrogen was supplied simultaneously with water to the immature leaves as they grew larger, and that this was related to the occurrence of type 1 sesame seed disease.

Scene at the time of harvesting Chinese cabbage.

　The incidence of sesamosis was higher on larger plants of both varieties, but this trend was more pronounced on the more abundant varieties.
(Figure 4).

　Nine Chinese cabbages of different plant weights were sampled for the sesamia-affected (●) and sesamia-poor (○) varieties, and total weight, outer leaf weight, and tuber weight were determined. As shown in Figure 5, the ratio of outer leaf weight to tuber weight was lower on larger plants of both varieties, and this tendency was more pronounced on the more heavily infested varieties. This trend was more pronounced in the more prolific variety, meaning that the larger plants were less productive in supplying material to the tuber. The plots were classified into three categories (3 replications) with base fertilizer nitrogen application rates of 10, 20, and 30 kg/10 a. The nitrogen application rate was determined by the amount of nitrogen applied after planting. Fertilizer nitrogen was applied at 5 kg/10a at 20, 30, and 40 days after planting.

　The results showed that the higher the amount of nitrogen applied, the heavier the plants were and the more sesamosis occurred (Figure 6). Even when plant weights were the same, the incidence of sesamosis was greater with higher amounts of base fertilizer nitrogen. This indicated that not only heavier plants but also higher nitrogen absorption was significantly related to higher incidence of sesamosis.

Histochemical changes in the development of sesamoidosis

　The morphological change process at the site of sesamoid development is shown in A-D.

A Sesamoidosis occurs mainly on the main vein surface of the tuberous leaves (inside the tubercle).
　Type 1 sesamosis occurred on leaves with an excessive supply of nitrate nitrogen in the main veins of immature leaves, and type 2 occurred significantly on the main veins at leaf level 25 to 45 at harvest time (Figure 2). In type 2, when the protoplast concentration in epidermal cells decreases, the concentration in the granules is relatively high, and the granules enlarge when water is supplied. When azo reagent or ammonia was applied to the area surrounding the granule enlargement, the area turned yellowish green, indicating the presence of chlorogenic acid (phenol).

B The area of intracellular granule enlargement gradually expanded, and the nucleus also enlarged. The area reacted with sulfanilic acid reagent to a light yellow color, indicating the presence of polyphenols, and a portion of the cell wall turned brown (Table 1).

C. The granules were enlarged and the browning area of the cell wall was enlarged, and at the same time, protoplasmic separation was observed in the surrounding cells. As the distribution range of polyphenols increased, the distribution of ascorbic acid decreased, and the surrounding cells showed enlarged intracellular granules. Note that too much nitrogen and too little sugar inhibits the reduction of polyphenols (Tables 1 and 2).

D. Three to six cell walls were completely browned, and all surrounding cells underwent protoplasmic separation. Because the protoplasmic separation made communication with the surrounding cells impossible, the number of browning cells did not increase, and they became sesame-like spots.

Effect of increased nitrogen fertilization on total sugar and ascorbic acid content

　The ratio of outer leaves to tuber leaves decreased with increasing nitrogen application (Figure 5), and nitrate nitrogen content
and tend to be deficient in total sugar content (Table 1).

　When nitrogen application is reduced over the entire period, the ratio of outer leaf weight to tuber weight increases, resulting in a higher sugar supply to the main vein. Since sugar (glucose) is a precursor of ascorbic acid (Table 2), it is considered that the polyphenol (brown) changes to phenol (colorless) when nitrogen application is reduced, and the incidence of sesame disease is relatively low.

　Concerning ascorbic acid at 55 days after planting in Table 2, the decrease in concentration at tuber leaf level 11 to 30, where the incidence of sesameosis is highest in the 20 and 30 kg/10a basal fertilizer treatments, was considered to be due to its use to change from polyphenols to phenols. The fact that the concentration did not decrease in the 10 kg/10a nitrogen-applied area, where the incidence of sesame seed disease is low, was considered to be due to the low incidence of sesame seed disease. A slight decrease was observed at leaf level 11 to 20 on the tuber leaf at 45 days after planting, but it was not extreme.

Effect of increased nitrogen application on K+ leakage from cells

　The K+ leakage from the main vein tissue fragments of each plot was investigated by dividing the plants by 1 to 10 leaf positions at the beginning of tuberization (Supplemental Data).
2). It has been reported that increased K+ leakage is caused by weakening and aging of the cell membrane (Tatsumi et al.)

　Here, K+ leakage was higher in leaves near the beginning of tuberization (leaf position 1-10) and in leaves with high incidence of sesamosis (Table 3). Leaves near the onset of tuberization were larger, had larger cells and higher nitrogen concentration (Figure 2), and were more advanced in ageing, which was thought to have increased K+ leakage. Therefore, the intracellular protoplasm concentration became thinner as water was supplied, and the difference between the intragranular solution concentration and the intragranular solution concentration increased, which caused the granules to enlarge to equalize the solution concentrations inside and outside the granules, which may have increased the occurrence of sesamphiphyllia.

References

●辰巳保夫・岩本光宏・頓田卓夫 1981
　ウリ科果実の低温障害と果実組織片からのイオン漏出について
　園学雑 50：108-113
●谷 利一 1965
　カキ炭疽病の病態生理学的研究，特に罹病果実の病態発現にあずかるペクチン質分解酵素の役割
　香川大農紀要 18：1-81
●豊田 栄・鈴木直治 1957
　稲熱病斑の組織科学的研究 ３ 病斑周辺の呼吸について
　日植病報 22：173-177
●松本美枝子 1987
　窒素追肥方法および貯蔵方法が収穫後のハクサイゴマ症の発生に及ぼす影響
　富山農技セ研報 1：17-23
●松本美枝子 1988
　ハクサイゴマ症の発生とその防止法に関する研究（１）
　ゴマ症発生中の形態及び組織化学的観察
　園学雑 57：206-214
●松本美枝子 1990
　ハクサイゴマ症の発生における基肥窒素施用量の影響
　土肥誌 61：345-352

　

　

No Soil - No. 27 Agriculture and Environmental Issues - Part 2
農地由来の窒素による水質汚濁

前 ジェイカムアグリ株式会社
北海道支店 技術顧問
松中　照夫

　As mentioned in the previous article, Japan's food self-sufficiency rate is low, so large amounts of crop nutrients such as nitrogen (N) contained in imported food and livestock feed are brought in from overseas. When large amounts of nutrients are brought into livestock farms in the form of feed and fertilizer, the nutrient cycle in the farm from soil to feed to livestock is disrupted, and nutrients are leaked into the surrounding environment. Among nutrients, N has a particularly negative impact on the environment. Even for arable farmers, when the amount of N brought into the farmland from outside exceeds the holding capacity of the soil, N is leaked into the surrounding environment. When N reaches rivers and groundwater, it causes water pollution, and when it reaches the atmosphere, it causes air pollution and contaminates the environment.

　In this issue, we will consider water pollution among the environmental pollution caused by N discharged from agricultural land. Air pollution will be discussed in the next issue.

1. eutrophication caused by water pollution

　Sources of substances that adversely affect rivers, lakes, marshes, and other bodies of water through groundwater and surface runoff can be broadly classified into two categories: point sources (specific sources), which can be identified, and areal sources (non-specific sources), which cannot. Point sources (specific sources) and non-specific sources (non-specific sources). In addition to N, other substances such as phosphorus (P) and organic substances are discharged from these sources and cause water pollution.

　N is usually given to farmland in the form of ammonia-form N (NH4+ -N). The given NH4+ -N is then converted to ammonium in the soil
P is also usually present in the soil as a loaded dihydrogen phosphate ion (H2PO4-). In other words, since both N and P are loaded ions, they are repelled by the soil's loading charge and are not easily retained in the soil. Therefore, N and P can easily leach into rivers and groundwater and become environmental pollutants.

　As they flow into lakes and rivers, their concentration increases and nutrients become enriched (this is called eutrophication). When eutrophication occurs, phytoplankton and planktonic cyanobacteria can bloom abnormally and cover the water surface as if green paint had been poured (Figure 1). This is the end point of water pollution.

2. sources of environmental pollutants

　(1) Point source contamination

　Typical examples of point source pollution are as follows. N concentrations in rivers passing near barns, piggeries, chicken coops, factories, sewage treatment plants, etc., groundwater pollution by N from manure mixtures stored in dugout manure pits (lagoons), and direct excretion of manure into rivers when grazing livestock use small rivers as watering holes. This is due to the fact that livestock grazing in small rivers use them as drinking places. Cases in various regions where NO3--N concentrations in well water near livestock facilities exceed drinking standards (10 mg per liter) are examples of point source pollution.

　(2) Surface source pollution

　Agricultural land, together with forests and urban areas, is treated as an expanse of land, i.e., a surface source. Pollution caused by areal sources is called areal source pollution. Because the source of this pollution is not specified, it is difficult to quantitatively determine where environmental pollutants originate and to what extent they are discharged into groundwater, rivers, and lakes. However, as the number of livestock per unit catchment area increases, the N concentration in river water increases because the amount of N released increases with the number of livestock (Figure 2). In other words, in the case of areal source pollution, an increase in the amount of pollutants discharged into the environment will certainly increase pollution.

Water Pollution Prevention Measures

　(1) Point source pollution control

　Point source pollution in livestock farms often occurs when manure overflows from storage facilities and leaks into the environment because the size of the storage facility does not meet the appropriate capacity for the number of animals being kept. To prevent this, manure storage facilities have been regulated by the "Law Concerning the Proper Management and Promotion of Utilization of Livestock Manure" since 1999, and penalties have been imposed on facilities that violate the law.

(2) Measures to prevent surface source contamination - (1) Establishment of allowable limit N

　Monitoring of NO3--N concentrations in groundwater seepage is important to prevent surface source pollution; NO3--N concentrations are determined by the balance result between the N given to the farmland and the N absorbed by the crop, and by the amount of water percolating through the soil. N absorbed by crops, and the amount of water that permeates the soil. Therefore, to prevent water pollution due to NO3--N infiltration, it is important to first keep the amount of N given to farmland within the carrying capacity of the environment (called the environmental capacity), where the natural self-cleansing capacity of the environment does not cause adverse effects of pollutants on the environment. This is called the environmental capacity. In addition, it is also important to avoid giving N to farmland at a time when N absorption by crops is not vigorous.

　Based on this concept, the European Union (EU) legally regulates the amount of N derived from livestock manure up to 170 kg/ha as an acceptable limit for agricultural land. In Japan, there is no such regulation for surface source pollution. Therefore, even if point source pollution is prevented by legal regulations on manure storage facilities, there is no limit to the amount of N that can be given to farmland, and thus prevention of areal source pollution is not thoroughly implemented. As a result, it has been pointed out that in nine prefectures with large numbers of livestock per unit area (Gunma, Kanagawa, Aichi, Tokushima, Kagawa, Nagasaki, Miyazaki, Kagoshima, and Okinawa), the estimated N concentrations discharged to groundwater all exceed drinking standards (Hojido et al., 2003).

(3) Measures to prevent surface source pollution - (2) Use of topographic chains and buffer zones

　As a concrete measure to prevent surface source pollution, it is effective to utilize a topographic chain that continues from high to low locations, for example, tea plantation - field - paddy field - wetland - river. The NO3--N that permeates underground from the high agricultural land is reused by crops in the low agricultural land, and finally converted into environmentally harmless nitrogen gas (N2) under reducing conditions (oxygen deficient conditions) in paddy fields and wetlands, which is then discharged into the atmosphere, thus preventing areal source pollution. This leads to the prevention of surface source pollution.

　In the case of runoff from agricultural land into water bodies as surface runoff, a pollution control measure is to increase the opportunity for environmental pollutants such as NO3--N to undergo natural purification before reaching rivers and lakes. For this purpose, wetlands and woodlands can be established near rivers to serve as buffer zones for the inflow of NO3--N into the rivers, thereby promoting natural purification and reducing NO3--N concentrations.

　The degree of remediation is greater when the distance between the source and the river is planted with crops, such as grassland, than in bare soil conditions. The required width of the buffer zone for this purpose is several to several tens of meters for point source pollution control and several tens of meters for area source pollution. However, since the effectiveness of this buffer zone varies greatly depending on land conditions, no specific standard for the required width of the buffer zone has been established.

　

　

General Index of Previous Editions of this Journal in 2023

<January issue
§Aiming to be a company that continues to contribute to Japanese agriculture
ジェイカムアグリ株式会社　代表取締役会長　浅野　進
§ Super-efficient fertilization of sudachi
徳島県立農林水産総合技術支援センター　資源環境研究課　新居　美香
No § Soil - No. 18
植物が難溶性物質を吸収するしくみ
－根から溶解を助ける物質を分泌する－
ジェイカムアグリ株式会社　北海道支店　技術顧問　松中　照夫

<February/March combined issue
§From clay content and carbon content of paddy soils
根こぶ病防除に必要な転炉スラグおよび
消石灰の施用量を計算する方法
東北農業研究センター　畑作園芸研究領域　野菜新作型グループ　山口　千仁
No § Soil - No. 19
吸収された窒素がタンパク質になるまで
－植物は必要なアミノ酸をすべて自給する－
ジェイカムアグリ株式会社　北海道支店　技術顧問　松中　照夫

<April issue
§ For paddy rice under variable climatic conditions
「苗箱まかせ」の有用性の考察
株式会社ファーム・フロンティア　取締役会長　藤井　弘志
No § Soil - No. 20
農産物のおいしさに影響する
タンパク質と炭水化物はトレードオフの関係
前 ジェイカムアグリ株式会社　北海道支店　技術顧問　松中　照夫

<May issue
§Melon and cucumber with magnesium
カリウムの欠乏症状と再移動
元 岡山大学大学院　自然科学研究科　桝田　正治
No § Soil - No.21
｢土は生きている」といわれるのはなぜ？
－土は生き物なのか
前 ジェイカムアグリ株式会社　北海道支店　技術顧問　松中　照夫

<June issue
§ IB fertilizer or collapsible coating to prevent runoff of fertilizer shells
肥料(Jコート)による被覆肥料代替効果の検証
愛媛県農林水産研究所　黒瀬　咲弥　　森重　陽子
§ In asparagus cultivation with coated urea fertilizer
窒素を３割減肥できる環境負荷低減施肥技術
熊本県農業研究センター　生産環境研究所　土壌環境研究室　山下　瑛
No § Soil - No.22
The role of soil in nurturing life on earth and preserving the global environment
前 ジェイカムアグリ株式会社　北海道支店　技術顧問　松中　照夫

<July issue
§ Coated fertilizer "J-Coat® Quick
ドローンによる水稲の局所追肥技術
石川県農林総合研究センター農業試験場　作物栽培グループ　専門研究員　有手　友嗣
§ Reports on production areas
Fuji Izu Agricultural Cooperative, Nirayama Agricultural Economy Center
における大玉トマトとイチゴのエコロング
施肥体系の紹介
静岡県富士伊豆農業協同組合　韮山営農経済センター　小鹿　浩睦
No § Soil - No. 23
原始地球に土はなかった
－こうして地球に土が誕生した
前 ジェイカムアグリ株式会社　北海道支店　技術顧問　松中　照夫

.
§ High-density seeding in paddy rice and
育苗箱全量施肥栽培を組み合わせた省力技術
熊本県農業研究センター　生産環境研究所　土壌環境研究室　田中　一成
§ Labor-saving fertilization method in the seedling stage of strawberry "Amaou
福岡県農林業総合試験場　筑後分場　龍　勝利
No § Soil - No.24
土は環境の産物である
－風化と生物の作用が岩石から土をつくる
前 ジェイカムアグリ株式会社　北海道支店　技術顧問　松中　照夫

<Oct.
§ In Ibaraki Prefecture's lotus root cultivation
窒素適正施肥技術の開発
茨城県農業総合センター　園芸研究所　土壌肥料研究室　鹿島　啓司
§Acid detergent soluble organic nitrogen content.
用いた有機質資材窒素肥効見える化の取り組み
農研機構　九州沖縄農業研究センター　暖地畜産研究領域　主席研究員　古賀　伸久
No § Soil - No. 25
農業が環境破壊の始まり
－人間活動と環境との関わり－
前 ジェイカムアグリ株式会社　北海道支店　技術顧問　松中　照夫

<Nov.
§J-coated fertilizer for paddy rice
全量基肥施肥と被覆樹脂殻の崩壊性
長野県農業試験場　上原　敬義　　吉川　直人
No § Soil - No.26
農業と環境問題－その１
わが国の窒素循環の問題点
前 ジェイカムアグリ株式会社　北海道支店　技術顧問　松中　照夫

<Dec.
§ Growth of Chinese cabbage and nitrogen application
元 富山県農業技術センター　松本　美枝子
No § Soil - No. 27
農業と環境問題－その２
農地由来の窒素による水質汚濁
前 ジェイカムアグリ株式会社　北海道支店　技術顧問　松中　照夫
§2023 General Table of Previous Editions of this Journal