§育苗箱全量施肥法における稲わら還元の影響について
Fukushima Prefectural Agricultural Center
半澤　勝拓
安田　優衣
§土のはなし－第32回
危機に瀕する世界の土－その２
不適切な人間活動が土を劣化させる
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

　

　

Seedling Box Total Fertilizer Application Method
稲わら還元の影響について

Fukushima Prefectural Agricultural Center
半澤　勝拓
安田　優衣

Introduction

　In recent years, rice paddy production has been changing to a "box fertilizer application" (hereinafter referred to as "box fertilization") for the purpose of reducing the amount of nitrogen applied to rice seedlings and saving labor.
The use of the "Aizu" region in Fukushima Prefecture is also widespread, especially in the Aizu region.

　一方で，水田への堆肥の施用量は，農林水産省の全国調査（農林水産省2022年）では，1984年に215kg/10aであったが，2020年は62kg/10aと30年間で約１/３に減少し，水田土壌の可給態窒素が２割の水田で不足していると指摘されており，地力の低下が懸念される。福島県では，2011年の東日本大震災以降，放射性セシウム対策として，土壌中の交換性カリ含量（25mg/100g以上)を維持するため，水田への稲わらの還元を指導しており，震災前より稲わら等の施用が増加し，堆肥と同様に地力の維持に寄与していると思われる。

　However, in recent years, yield and quality decline due to abnormally high temperatures during the growing season has become a problem. In the case of box fertilization, because the nitrogen leaching of the fertilizer used is highly temperature-dependent, there are concerns that under extremely high temperature conditions, the fertilizer efficacy may be delayed or not sustained until the latter half of the crop's ripening period. In addition, there is concern about the rapid decomposition of rice straw due to extremely high temperatures, resulting in abnormal straw reduction and the generation of methane gas, which may lead to growth disorders.

　Therefore, as basic data for fertilizer management under high temperature conditions, we decided to investigate the effect of continuous use of rice straw in box fertilization using "Seedling Box Makase".

2. Testing Method

　農業総合センター内の水田において2020年，2021年の２年間試験を行った。
　供試水田は，稲わら還元によるカリの施用効果も検討するため，土壌中の交換性カリ含量が15mg/100g以下で，2017年から毎年，収穫後に稲わらを全量搬出している水田と稲わらを還元している水田の２筆を選定した。

　試験は，本県のコシヒカリの標準的な施肥体系(窒素：基肥４kg/10a，追肥２kg/10a，計６kg/10a)を慣行栽培として，｢苗箱まかせＮ400‒80｣，｢苗箱まかせＮ400‒Ｂ30」の２種類の肥料を使用して，耕種概要（表１）および試験区の構成（表２）のとおり実施した。

Results and Discussion

(1) Summary of growing season weather

　2020年の平均気温は，５月１半旬が平年より５℃高かったが，５月４半旬から５半旬に10℃以下の日があったため，５月の月平均は平年より２℃低かった。６月は平年より1.4℃高く，７月は1.2℃低かったが，出穂後の８月４半旬以降は平年より2.3℃高く，日照時間も平年比127％と長かった。

　2021年は，５月２半旬まで平年より約２℃低かったが，６月は平年より0.9℃，７月は0.6℃高かった。８月３半旬は，平年より5.4℃低く，８月３半旬以降は平年より1.8℃低かった。また日照時間は，８月３半旬以降は平年比76％と短く，特に８月３半旬から５半旬は平年比45％とかなり短かった。（図１)。

(2) Seedling quality at transplantation

　2020年，草丈は，苗箱80区および苗箱Ｂ30区が慣行区より大きかった。2021年，草丈に区間の有意差は認められなかったが，乾物重は，苗箱Ｂ30区がやや小さかった。葉齢は，苗箱80区と苗箱Ｂ30区が慣行区より大きかった（表３)。2020年は，育苗期間が32日であり，５月１半旬の高温により，「苗箱まかせ」の窒素が早く溶出したため，苗箱80区および苗箱Ｂ30区の草丈が大きかったが，2021年は，育苗期間中の気温が平年以下であったため，育苗期間中に「苗箱まかせ」の窒素はほとんど溶出せず，葉齢が進んでも草丈の伸長は慣行区並であったと考えられた。

(3) Growth in rice paddies

　2020年，移植40日後の生育は，稲わら無施用では，草丈は苗箱80区が33.6cm，慣行区が32.5cmと苗箱80区が慣行区より長く，茎数は 苗箱80区が15.7本/株，慣行区が16.3本/株と苗箱80区が少なかった（表４，図２，図３)。

　稲わら施用では，草丈は31.3～31.5cmであり，慣行わら区，苗箱80わら区，苗箱Ｂ30わら区ともほぼ同じであったが，茎数は，苗箱80わら区が13.7本/株，苗箱Ｂ30わら区が14.7本/株，慣行わら区が15.9本/株と稲わら無施用と同様に箱施肥の区が慣行施肥の区より少なかった。

　移植60日後では，苗箱80区は，茎数も慣行区より多かったが，稲わら施用では，草丈は慣行わら区＜苗箱80わら区＜苗箱Ｂ30わら区，茎数は苗箱80わら区＜苗箱Ｂ30わら区＜慣行わら区，葉色は慣行わら区＜苗箱Ｂ30わら区＜苗箱80わら区の順となり，草丈は40日後より区による差が大きく，茎数は区による差が小さかった。

　成熟期は，稲わら無施用は移植60日後と同様に稈長，穂数とも苗箱80区＞慣行区であったが，稲わら施用では，稈長は苗箱80わら区＜苗箱B30わら区＜慣行わら区，穂数は苗箱80わら区＜慣行わら区＜苗箱Ｂ30わら区の順であり，苗箱80わら区が稈長，穂数とも最も低かった。

　2021年，移植40日後の草丈，茎数，葉色の値は全て，苗箱80区＜慣行区，稲わら施用では，苗箱Ｂ30わら区＜苗箱80わら区＜慣行わら区の順であり，稲わら無施用及び施用とも箱施肥区が慣行施肥区より小さかった（表４，図２，図３)。

　移植60日後の草丈，茎数は，稲わら無施用では，移植40日後と同様に苗箱80区＜慣行区であった。稲わら施用では，苗箱Ｂ30わら区＜苗箱80わら区＜慣行わら区の順となったものの苗箱Ｂ30わら区と苗箱80わら区の差はわずかであった。葉色は，苗箱80区＞慣行区，苗箱Ｂ30わら区＞苗箱80わら区＞慣行わら区の順であった。草丈，茎数は，稲わら無施用及び施用とも箱施肥の区が慣行施肥の区より小さかったが，葉色は逆に箱施肥の区が慣行施肥の区より大きかった。

　成熟期は，稲わら無施用は移植60日後と同様に稈長，穂数とも苗箱80区＜慣行区であった。稲わら施用では，稈長は苗箱80わら区＜苗箱Ｂ30わら区＜慣行わら区の順，穂数は苗箱Ｂ30わら区＜苗箱80わら区＜慣行わら区の順となり，稲わら無施用及び稲わら施用ともに稈長，穂数は，箱施肥の区が慣行施肥の区より低かった。

　また，2020年，2021年の両年とも移植40日後の茎数は，慣行区＞慣行わら区，苗箱80区＞苗箱80わら区，苗箱Ｂ30わら区であり，稲わら施用した区の茎数が少ない傾向が見られた。

(4) Yield and yield components

　2020年，一穂籾数（粒/穂）は，慣行区（64.7）＜苗箱80区（76.0)，慣行わら区（63.7）＜苗箱Ｂ30わら区（68.7）＜苗箱80わら区（70.7）であり，稲わら無施用及び施用とも箱施肥の区で多かった。登熟歩合（％）は，慣行区（90.6）＞苗箱80区（88.9)，慣行わら区（76.1）＜苗箱80わら区（83.6）＜苗箱Ｂ30わら区（87.2）であり，稲わら無施用では，慣行施肥が高く，稲わら施用では，箱施肥の区が高かった。

　精玄米重（kg/10a）は，慣行区（55.1）＜苗箱80区（57.9)，苗箱80わら区（55.0）＜苗箱Ｂ30わら区（58.6）＜慣行わら区（61.0）であり，稲わら無施用では，箱施肥が高く，稲わら施用では，慣行施肥が高かった（表５)。

　2021年，一穂籾数（粒/穂）は，慣行区（76.9)＜苗箱80区（78.5)，慣行わら区（80.4）＜苗箱Ｂ30わら区（82.9）＜苗箱80わら区（83.8）であり，2020年と同様に稲わら無施用及び施用とも箱施肥の区で多かった。登熟歩合（％）は，慣行区(77.9）＜苗箱80区（78.7)，慣行わら区（70.7）＜苗箱Ｂ30わら区（72.7）＜苗箱80わら区（75.6）であり，稲わら無施用では，慣行施肥が高く，稲わら施用では，箱施肥の区が高かった。

　精玄米重（kg/10a）は，苗箱80区（39.8）＜慣行区（46.0)，苗箱80わら区（41.1）＜苗箱Ｂ30わら区（42.1）＜慣行わら区（43.0）の順で，稲わら無施用及び施用とも慣行施肥の区が高かった（表５)。

　なお，㎡当たり籾数（×100粒/㎡）は，2020年は慣行区（188）＜慣行わら区（245)，苗箱80区（220）＜苗箱80わら区（243）であり，2021年は慣行区（347）＞慣行わら区（322)，苗箱80区(293）＜苗箱80わら区（303）であり，箱施肥は両年とも稲わら施用した区が多かったが，登熟歩合は，両年とも慣行施肥，箱施肥の区とも稲わら施用した区で低かった（表５)。

(5) Changes in soil nutrients

　試験開始前（2020年４月）と試験終了後（2021年９月）の土壌化学性の変化を見ると（表６)，可給態窒素は，稲わらの無施用区（慣行区，苗箱80区）では試験開始から徐々に低下しているが，稲わら施用区（慣行わら区，苗箱80わら区，苗箱Ｂ30わら区）では2020年９月から2021年４月に増加する傾向が見られた。

　また，交換性カリも稲わら施用区（慣行わら区，苗箱80わら区，苗箱Ｂ30わら区）は，稲わら無施用区（慣行区，苗箱80区）に比べ2020年９月から2021年４月に増加する傾向が見られた。

　可給態リン酸は，稲わら無施用区（慣行区，苗箱80区）が稲わら施用区（慣行わら区，苗箱80わら区，苗箱Ｂ30わら区）より高い値で推移し，稲わら施用の影響は判然としなかった（図４)。

(6) Consideration

　In 2020, although there was an effect of low temperatures immediately after transplanting, growth 40 days after transplanting was inferior to conventional fertilization in the box-fertilized plot, regardless of whether rice straw was applied or not, similar to the results reported by Ueno (2015).

　これは，６月上旬時点では，｢苗箱まかせ」の肥効は，慣行施肥に比較して明らかに低く経過するためであり，本調査のように乾土効果による窒素発現量が小さい水田では，より顕著になると考えられた。

　また，稲わら施用による影響を見ると，稲わら施用した区は，両年とも移植40日後の茎数が少ないことが認められ，特に箱施肥の区で顕著であり，稲わら施用により，初期生育が抑制されるという既存の報告と一致した（千葉ら1980，安藤ら1986，前田1983)。　安藤ら（1986）は，水田に施用された稲わら中の窒素は，移植後の低温条件でも無機化されること，稲わら施用により，肥料由来の窒素が稲わらに取り込まれ減少するが，その量はわずかであると報告している。

　The total nitrogen content in the soil of the test paddy in this study was 0.09-0.01%, which was considerably lower than the 0.30% in the rice paddy studied by Ando et al. The available nitrogen in the soil of the test paddy before fertilizer application (April) was also low at 7.3-9.7 mg/100g. This suggests that the proportion of fertilizer-derived nitrogen incorporated into the rice straw was quite high because the effect of dry soil before watering was small and the inorganic nitrogen content in the soil was low in the early growth stage of the test paddy was small.

　また本結果では，2020年，2021年の両年とも移植40日後の葉色値は，苗箱80区より苗箱80わら区，苗箱Ｂ30区が低いことから，稲わら施用した箱施肥区は，移植後の窒素吸収量が稲わら無施用の区より少なかったため，生育が劣ったと考えられた。

　Ueno (2014) stated that the initial growth of paddy rice is closely related to the dry-soil effect, and that in paddy fields with low nitrogen soil fertility and low dry-soil effect, box fertilization alone is not sufficient to ensure initial growth, and a combination of side-row fertilization and fertilization at emergence is necessary to achieve the target yield. Therefore, when box fertilization is used, it is important to understand the amount of available nitrogen in the paddy soil and to prepare the soil to increase the expression of nitrogen by the dry-soil effect.

　The suppression of early growth by rice straw application may be due to oxygen consumption in the soil by rice straw decomposition, rapid reduction of the soil, and generation of methane and hydrogen sulfide, which may cause poor establishment, delayed root growth, and inhibition of nutrient absorption.

　次に，穂数についてみると，上野（2015）は，目標収量の確保には，穂数を得るために初期茎数の早期確保が重要であるが，最高茎数をセーブして有効茎歩合を高めることも重要であり，窒素的地力が高い土壌では，穂数を確保できると述べている。

　Because this study was conducted on soils with low nitrogenous soil fertility, the low number of stems at 40 days after transplanting tended to result in a low number of ears. In particular, in 2020, the number of early stems was lower in the box-fertilized area than in the conventionally fertilized area, and the number of stems was also lower in the area where rice straw was applied in both the conventionally and box-fertilized areas.

　Straw application has a negative effect on the number of ears because of the low number of stems 40 days after transplanting, but the results show that the number of ears in 2020 was higher in the 80 straw seedling box than in the 80 seedling box, and the number of rice paddy was higher in the 80 straw seedling box than in the 80 seedling box in both 2020 and 2021.

　Chiba et al. (1980) reported that the amount of mineralized soil nitrogen increased rapidly with increasing temperature in rice-straw intercropped fields, and that it was expressed mainly during the juvenile ear formation period. This is assumed to be because the nitrogen expressed was absorbed by the rice plants and acted to secure the effective number of stems and rice paddy.

　このため，窒素的地力が低い土壌において，箱施肥を行う場合，稲わら施用は，㎡当たりの穂数や籾数の確保に効果があり，コシヒカリなどの穂数タイプの品種には有効と考えられた。

　また，苗箱80わら区と苗箱Ｂ30わら区の穂数と一穂籾数を比較すると，2020年は穂数と一穂籾数とも，ほぼ同じ穂数，一穂籾数が確保されていたが，2021年は一穂籾数は同等であったのに対し，穂数は，苗箱Ｂ30わら区が苗箱80わら区に比べ明らかに少なかった。これは，2021年の出穂日が8/10であり，2020年の8/15より５日早まったためと考えられた。｢苗箱まかせＮ400‒Ｂ30」の溶出期間は100日であり，2021年の幼穂形成期は7/18頃であることから推察すると，苗箱Ｂ30わら区では，幼穂形成期までに肥料由来窒素の溶出が十分でなく，肥料由来窒素の溶出期間80日の苗箱80わら区と同等の穂数が確保出来なかったと考えられた。

　Therefore, under high temperature conditions, the ear formation period is expected to be accelerated. Therefore, the application of rice straw was considered effective in box fertilization to supplement fertilizer efficacy, taking into consideration the duration of fertilizer efficacy to secure the number of ears.

　The maturity yield tended to be lower when rice straw was applied, both with conventional fertilizer and with box fertilizer. This may be due to the fact that the application of rice straw increased the number of rice paddy, but did not provide sufficient nitrogen to increase the maturity yield after ear emergence.

　本県において1985年～2005年の21年間，稲わらを連用した結果では，６％増収する結果が得られている（三浦ら2022)。しかし本結果では，2020年の慣行施肥においては，稲わら施用により精玄米重が増加しているが，箱施肥は両年とも少なかった。これは，稲わらの連用期間が短く，土壌の化学性も三浦らの報告のような地力の差が無かったためと考える。

　On the other hand, considering Chiba et al.'s (1980) report that in rice paddy fields with long-term continuous application of rice straw, the application of ear fertilizer promotes mineralization of soil nitrogen and increases the uptake of soil-derived nitrogen until late in the season, it is expected that the yield of box fertilization will also turn to increase with continued continuous application of rice straw. Furthermore, the continuous use of rice straw also slightly increased the availability nitrogen and exchangeable potassium in the present results, and is also effective in maintaining exchangeable potassium, as reported previously (e.g., Miura et al. 2022).

　Chiba et al. (1980) reported that reducing rice straw, applying lime nitrogen and soil improvement materials simultaneously, and fall plowing in the fall season are effective in increasing soil nitrogen. The following is a brief summary of the results of the study.

Summary

　In rice paddies with low nitrogen soil fertility, box fertilization may not ensure the amount of nitrogen necessary for early growth, resulting in lower yields.

　However, in rice paddies with low nitrogen fertility, it is necessary to promote the decomposition of rice straw before watering by reducing the straw in the fall and plowing in the fall to suppress early stage of growth and to ensure stable ear number.

　Rice farming operations are becoming larger and larger, but new measures must be taken to counter soaring prices of fertilizers and other commodities and to realize the Green Food System Strategy, which requires fertilizer application technology that enables further labor savings and cost reduction.

　Under these circumstances, box fertilization is a highly effective fertilizer application method, and is considered to be a labor-saving, low-cost, and stable production technology. In order to utilize box fertilization as a more effective technology, it is necessary to conduct soil diagnosis and select the type of fertilizer for box application, "Seedling Box Leave," taking into consideration the fertilizing effect of compost and the amount of available nitrogen in the soil, as well as the nutrients related to soil fertility, such as the content of available nitrogen.

　In conclusion, not limited to box fertilization, the most important thing to achieve stable production is to continue to cultivate the soil to increase soil fertility through the continuous use of organic materials such as rice straw and compost.

References

（１）上野正夫．苗箱施肥における本田生育の特徴と留意点．農業と科学．第667号，p8－p12．(2015）

（２）千葉満男，島津了司，武藤和夫，内田修吉．水田における稲わら施用と稲作の安定化．岩手県立農業試験場研究報告　第22号，81‒117.(1980）

（３）安藤　豊，庄子貞雄，及川　勉，菅野忠教．水田土壌中での稲わら分解と窒素の挙動．日本土壌肥料学雑誌　第57巻，第４号，359‒364.(1986）

(4) Maeda, Kenichi. Quantitative Evaluation of the Behavior of Nitrogen Applied to Paddy Fields. Agricultural Research Center Research Report 1, 121-193 (1983).

(5) UENO, Masao. Nitrogen Fertility of Paddy Soils and the Mechanism of Mineralization. Agriculture and Science. No. 658, p1-p5.(2014).

(6) Miura, Y., Matsumoto, Y., Sasagawa, M., et al. (6) Miura, Y., Matsumoto, Y. and Sasakawa, M. Effects of long-term continuous use of three elements, organic matter and soil amendments on rice yield and paddy soil chemistry. Fukushima Prefectural Agricultural Science Research Report 13, 33-48.(2022)

　

　

No Soil - No. 32
危機に瀕する世界の土－その２
不適切な人間活動が土を劣化させる

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

　Soil is the foundation of food production. Without soil conservation, food security is impossible and advanced civilization cannot be maintained. In my previous article, I said that we must ask ourselves how we can make the most of this lesson today. Unfortunately, I do not believe that this lesson is being fully applied. This is because soil degradation is still progressing around the world. In this issue, I would like to discuss inappropriate human activities that are the main cause of this degradation.

1. soil degradation due to human activities

　Degradation of food-producing farmland refers to the phenomenon in which the soil is degraded and crop productivity is significantly reduced or eliminated as a result of inappropriate soil management and excessive deprivation of the soil in order to increase productivity.

　Soil is a product of its environment. Soil changes and is created in the most stable direction under a given environment. Therefore, as long as human activities are within the range of such changes, the soil itself does not deteriorate. When human activities cause changes in the soil that are greater than those caused by the environment, the soil deteriorates. Although the data on soil degradation caused by human activities are somewhat old, it is estimated to be about 2 billion hectares, or about 17% of all vegetated areas in the world (Figure 1).

最近，これと同様のデータの公開がない。しかし状況はさらに悪化しているようだ。国連食糧農業機関（FAO）事務総長シルヴァが国際土壌デーと国際土壌年の発足にあたり，世界の土の３分の１が劣化しているとの驚くべきメッセージを発表している（Silva，2014)。

　Major human activities that degrade the soil include improper agricultural management through over-cultivation, overgrazing that allows livestock to graze more than the regenerative capacity of wild grasses, and over-cutting of forests.

2. human activities that degrade agricultural soil

1) Improper agricultural management - over-cultivation

　Convenient land suitable for agriculture is cultivated and turned into farmland at an early stage. However, the more such land is cultivated, the more people live there. In order for humans to live, land is necessary. Industrial land is also necessary. At present, most of the land suitable for agriculture has already been developed, and the development of agricultural land has reached its limits. Therefore, as the population continues to grow, the world's per capita cereal production area continues to decline. As a result, increased food production has to be expected on a per-unit-area basis.

　In developing countries, where agriculture is practiced with a high degree of abandon, excessive cultivation is repeated with inadequate nutrient supply and soil management, resulting in overuse of the soil. In the past, slash-and-burn shifting cultivation was reused only after both soil fertility and reforestation had been sufficiently restored. Recently, however, this is no longer possible. This is because the land area for shifting cultivation has decreased due to the increase in population. In particular, over-cultivation in arid and semi-arid regions leads to land desertification (Igasaki, 2015). Furthermore, the introduction of inappropriate irrigation in these zones can easily lead to soil salinization as seen in Mesopotamia.

　On the other hand, intensive farming areas tend to provide more nutrients than necessary in the hope of increasing yields. This leads not only to environmental pollution but also to soil salinization caused by excess nutrients, making it impossible to grow crops. This improper management of agriculture leads to soil degradation.

(2) Overgrazing

　Developing countries in Asia and Africa have used the wild grasses of the land for grazing use by livestock. This is because they provide a living food reserve for livestock. Their manure is used as a source of nutrients for the soil, and dried manure is sometimes used as fuel. However, as the number of grazing livestock increases with population growth, grazing livestock forage for more wild grasses than they regenerate, resulting in a decrease in the density of wild grasses, which exposes the soil. This is the state of overgrazing.

　Under overgrazing conditions, not only is the soil exposed, but it also becomes hard and compacted by the treading pressure of livestock. The hard soil surface prevents rainwater from infiltrating the soil, and surface runoff erodes the topsoil, accelerating degradation. Wild grasses also play an important role in helping the soil retain water. However, when wild grasses are lost from the soil due to overgrazing, the soil becomes arid and desertified.

(3) Loss of forests

　Forests also play an important role in retaining soil moisture. However, population growth in developing countries increases the demand for wood for housing and fuelwood, and the use of wood expands to include important forests. The expansion and inappropriate use of slash-and-burn cultivation areas and conversion of land to pastureland also lead to the gradual decline of forests. The loss of forests that follows the decline also contributes to soil degradation. In particular, the loss of forests in tropical rainforest areas causes further soil degradation due to soil erosion.

　2020年の地球上は，陸地のおよそ31％に相当する41億haが森林（植林地を含む，以下同じ）で覆われている（FAO，2021)。1990年から2020年の30年間で比べると，増加した森林面積は6,860万haだったのに対し，２億4,610万haが消失している。

つまり，この30年間で世界から失われた正味の森林面積は１億8千万haに達し，わが国の国土面積（3,778万ha）の約５倍に相当する。これは，毎年600万haもの森林が消失していったことになる。ただし，世界の森林消失面積は全体でみると，1990年以降，減少しつつある。

　森林消失面積が大きかったのは南アメリカ地域で，1990年からの30年間に１億2,950万haも消失した。このうちの大部分はブラジルで失われた9,230万haである。ブラジルでは平均するとこの30年間，毎年308万haも消失したことになる。アマゾンの熱帯雨林地帯での違法で不適切な過剰伐採が主な要因である。この消失速度は，わが国の全森林面積（2,494万ha，2020年FAO）が，およそ８年で失われることを意味する大きな値である。アフリカ地域でも1990年以降の30年間で，１億１千万haの森林が消失した。他の地域と異なり，1990年以降の10年ごとの消失面積に減少傾向がなく，直近の2010年からの10年間には3,940万haが失われている。

　In Asia, on the other hand, forest area increased by 52.7 million ha in the 30 years from 1990. This is largely due to the fact that China increased its forest area by 62.8 million ha during the same 30-year period through afforestation activities (Figure 2), and India also expanded its forest area by 8.22 million ha during the same period. Conversely, Indonesia lost 26.4 million ha of forest area during the same period. This is the result of continued over-cutting of Indonesia's tropical rainforests and peat forests as raw materials for paper production for Japan and other countries (Sagara, 2021).

　Excessive logging in tropical rainforests in Brazil, Indonesia, and other countries has a significant negative impact not only on the soil but also on the global environment. I will discuss this on another occasion.