【発明の詳細な説明】[Detailed description of the invention]
本発明は重粘土質土壌改良剤に関する。
耕作面積の乏しい我国においては、単位面積当
りの農作物の生産性を高めて自給率を向上させる
と共に不良地を改良して耕地面積の拡大を図るこ
とは、今後の重要な課題で、我国にはこのような
不良地として広大な面積の重粘土質土壌が存在す
る。
重粘土質土壌は耕耘作業が極めて困難なばかり
でなく、耕耘しても降雨あるいは潅水により、土
壌が粘着硬化して水及び空気の流通が殆んど不可
能に近い状態になるため、作物の生育が著しく阻
害される。かかる重粘土質土壌の改良方法とし
て、塩化アルミニウム、硝酸アルミニウム、硫酸
アルミニウムあるいは有機酸アルミニウム更には
アルミニウムを３価の鉄で一部置換した塩を使用
する方法が知られているが、無機のアルミニウム
塩改良剤を使用するときは土壌PHが低下し、電気
伝導度（以下、単にECと略記する）が上昇し、
これらに起因して有用なCa、Mg、Ｋ等の肥料塩
類が溶脱し、従つて多くの後処理を必要とし必ず
しも経済的でない。
一方、有機酸アルミニウム塩はPHの低下、EC
の上昇を抑制しうる点では望ましいが団粒化効果
に於て、無機のアルミニウム塩に若干劣る。
そこで本発明者らは土壌のPHの低下及びECの
上昇を招来することなく、有機酸アルミニウム塩
の団粒効果を更に高める方法について検討した結
果、以下に詳記する本発明に到達したものであ
る。
即ち、本発明は水溶性カルボン酸塩からなる
Alイオンと、水溶性カルボン酸塩又は無機酸塩
からなるNH4イオンと、水溶性カルボン酸イオン
とを含有し、Ｃ／Ｎ比が５〜30である重粘土質土
壌改良剤に関する。本発明の対象となる重粘土質
土壌は国際土壌分類学会の分類法による粘土粒子
（0.002mm以下）含量が25重量％以上含まれている
土壌である。
本発明の改良剤としては水溶性カルボン酸イオ
ンを含有する有機酸（以下、単に有機酸と略記す
る）例えば、ギ酸、酢酸、シユウ酸、クエン酸等
のアルミニウム塩と有機酸のアンモニウム塩の混
合物が最適の改良剤として例示され、概して液状
で使用することが望ましいが、乾燥し、粉末化し
たものであつてもよい。
而して、有機酸のアルミニウム塩は塩基性塩で
あつても、正塩であつてもよく、あるいはアルミ
ニウムに対し過剰の有機酸を含有したものであつ
てもよい。また、アンモニウムの供与方法として
は上記の如く、有機酸アンモニウムの形態で供与
することが最も望ましいが、無機酸のアンモニウ
ム塩、例えば塩化アンモニウム、硝酸アンモニウ
ム、りん酸アンモニウム、硫酸アンモニウムとし
ても供与することができる。
次にAlイオン、NH4イオン、有機酸イオンの割
合について述べればAl／有機酸（モル比）は概
ね0.1〜1.5の範囲にあり、有機酸に由来するＣと
NH4に由来するＮのＣ／Ｎ比は５〜30にあること
が望ましい。即ち、かかる範囲でAlイオン、NH4
イオン、有機酸イオンを使用するときは有機酸ア
ルミニウム単味より更に団粒化効果を高めること
ができる。
尚、本発明に於てAlイオンに代えて一部３価
のFeイオンを使用することができるが、その代
替しうる範囲はAl／Feモル比で0.5以下である。
本発明の土壌改良剤の重粘土質土壌の使用割合
について言えば土壌の種類、改良剤の組成により
異なるが概ねR2O3（但し、ＲはAlまたはAlと３
価のFeを示す）として10a当り（土壌100t）50〜
800Kgである。
即ち、本発明改良剤の添加量が下限を下廻ると
本発明の効果を期待することが出来ず、一方上限
を上廻る場合、格別支障なはいが使用量に比例す
る程の団粒化効果が期待できず経済的でない。
以下に本発明の実施例を挙げて更に説明する。
実施例 １
重粘土質土壌（粘土50.3％、シルト38.6％、細
砂8.5％、粗砂2.6％、組成；Al2O330.1％、
Fe2O31.1％、SiO254.5％）を風乾した後、風乾土
壌100重量部に酢酸アルミニウム水溶液
（Al2O36.06％、酢酸21.4％）と酢酸アルミニウム
25％水溶液を下表のＣ／Ｎ比となるように混合
し、この混合水溶液に水を加えてAl2O30.67％の
水溶液をつくり、該水溶液を30重量部添加混合
し、ビニール袋に密封して室温で28日間放置後耐
水性団粒化試験を行つた。その結果は次表の通り
である。
＜耐水性団粒化試験方法＞
砂層上部に敷いた紙上に供試土壌20ｇを薄く
広げ、紙の下0.5cmの深さまで水を入れて供試
土壌を24時間毛管湿潤させた。この供試土壌を水
200mlに入つた300ml容三角フラスコに入れて、24
時間放置し、次いで往復型振とう機（100回／
分）で２時間振とうした後、ヤーダーの篩別装置
（篩目径2.0、1.0、0.5、0.25、0.1mm、振幅3.8cm、
振とう速度25回／分）を用いて25分水中篩別し、
各篩上に残存した土壌を合一し、乾燥した後、重
量（Ａとする）を測定した。
次にこの乾燥土壌を団粒が崩壊する程度に軽く
破砕した後、上記と同様の水中篩別を行ない、各
篩別上に残存した一次粒子を合一し、乾燥した
後、重量（Ｂとする）を測定し、次式より耐水性
団粒化率を求めた。
耐水性団粒化率＝Ａ−Ｂ／２０×100（重量％）
The present invention relates to a heavy clay soil conditioner. In Japan, where cultivated area is scarce, increasing the productivity of agricultural crops per unit area to improve the self-sufficiency rate, as well as improving poor land and expanding the cultivated area are important challenges for the future. A vast area of heavy clay soil exists as such poor land. Not only is heavy clay soil extremely difficult to till, but even if it is tilled, rain or irrigation will cause the soil to stick and harden, making it almost impossible for water and air to circulate, making it difficult to grow crops. Growth is severely inhibited. Known methods for improving such heavy clay soil include using aluminum chloride, aluminum nitrate, aluminum sulfate, organic acid aluminum, and salts in which aluminum is partially replaced with trivalent iron; however, inorganic aluminum When using salt amendments, soil PH decreases, electrical conductivity (hereinafter simply abbreviated as EC) increases,
Due to these factors, useful fertilizer salts such as Ca, Mg, and K are leached out, and therefore many post-treatments are required, which is not necessarily economical. On the other hand, organic acid aluminum salts cause a decrease in PH and EC
Although it is desirable in terms of being able to suppress the increase in the temperature, it is slightly inferior to inorganic aluminum salts in terms of agglomeration effect. Therefore, the present inventors investigated a method to further enhance the agglomeration effect of organic acid aluminum salts without causing a decrease in soil PH or an increase in EC, and as a result, they arrived at the present invention as detailed below. be. That is, the present invention consists of a water-soluble carboxylic acid salt.
The present invention relates to a heavy clay soil conditioner containing Al ions, NH 4 ions consisting of water-soluble carboxylate or inorganic acid salts, and water-soluble carboxylate ions, and having a C/N ratio of 5 to 30. The heavy clay soil that is the object of the present invention is soil containing 25% by weight or more of clay particles (0.002 mm or less) according to the classification method of the International Society of Soil Taxonomy. The improving agent of the present invention is an organic acid containing a water-soluble carboxylic acid ion (hereinafter simply abbreviated as organic acid), for example, a mixture of an aluminum salt such as formic acid, acetic acid, oxalic acid, citric acid, and an ammonium salt of an organic acid. are exemplified as optimal modifiers, and are generally preferred to be used in liquid form, but may also be used in dry and powdered form. The aluminum salt of an organic acid may be a basic salt, a normal salt, or may contain an excess of organic acid relative to aluminum. As for the method of donating ammonium, as mentioned above, it is most desirable to donate it in the form of organic acid ammonium, but it can also be donated as an ammonium salt of an inorganic acid, such as ammonium chloride, ammonium nitrate, ammonium phosphate, or ammonium sulfate. . Next, regarding the ratio of Al ions, NH 4 ions, and organic acid ions, Al/organic acid (molar ratio) is approximately in the range of 0.1 to 1.5, and C derived from organic acids and
The C/N ratio of N derived from NH 4 is desirably in the range of 5 to 30. That is, in this range, Al ion, NH 4
When ions or organic acid ions are used, the agglomeration effect can be further enhanced than when organic acid aluminum alone is used. In the present invention, some trivalent Fe ions can be used in place of Al ions, but the range in which they can be substituted is within the Al/Fe molar ratio of 0.5 or less. The proportion of heavy clay soil used in the soil conditioner of the present invention varies depending on the type of soil and the composition of the conditioner, but is generally R 2 O 3 (where R is Al or Al and 3
50~ per 10a (100t of soil)
It is 800Kg. That is, if the amount of the improving agent of the present invention is below the lower limit, the effect of the present invention cannot be expected, whereas if it is above the upper limit, the agglomeration effect will be proportional to the amount used, although there will be no particular trouble. cannot be expected and is not economical. The present invention will be further explained below with reference to Examples. Example 1 Heavy clay soil (clay 50.3%, silt 38.6%, fine sand 8.5%, coarse sand 2.6%, composition; Al 2 O 3 30.1%,
After air-drying 1.1% Fe 2 O 3 , 54.5% SiO 2 ), add an aqueous solution of aluminum acetate (6.06% Al 2 O 3 , 21.4% acetic acid) and aluminum acetate to 100 parts by weight of the air-dried soil.
Mix a 25% aqueous solution to the C/N ratio shown in the table below, add water to this mixed aqueous solution to make a 0.67% Al 2 O 3 aqueous solution, add 30 parts by weight of the aqueous solution, mix, and put into a plastic bag. After being sealed and left at room temperature for 28 days, a water resistance agglomeration test was conducted. The results are shown in the table below. <Water Resistance Agglomeration Test Method> 20 g of test soil was spread thinly on paper spread over the sand layer, and water was poured to a depth of 0.5 cm below the paper to capillary moisten the test soil for 24 hours. Water this test soil.
Pour into a 300ml Erlenmeyer flask containing 200ml and add 24
Leave it for a while, then use a reciprocating shaker (100 times/
After shaking for 2 hours using a Yarder sieving device (sieve size 2.0, 1.0, 0.5, 0.25, 0.1 mm, amplitude 3.8 cm,
Sieve under water for 25 minutes using a shaking speed of 25 times/min.
The soil remaining on each sieve was combined and dried, and then the weight (referred to as A) was measured. Next, this dry soil is lightly crushed to the extent that the aggregates disintegrate, and then it is sieved underwater in the same way as above, the primary particles remaining on each sieve are combined, dried, and the weight (B) ) was measured, and the water-resistant agglomeration rate was determined from the following formula. Water resistance agglomeration rate=A-B/20×100 (weight%)
【表】
実施例 ２
実施例１の風乾重粘土質土壌100重量部にギ酸
アルミニウムとギ酸アンモニウムの混合水溶液
（Al2O31.01％、ギ酸6.2％、Ｃ／Ｎ比15）30重量
部を混合し、実施例１と同様の方法により14日間
放置後耐水性団粒化率を測定した結果25.1％であ
つた。一方、比較例としてギ酸アルミニウム水溶
液（Al2O31.0％、ギ酸5.7％）を風乾重粘土質土
壌100重量部に対し30重量部添加し、上記と同様
の操作を行い耐水性団粒化率を測定した結果20.4
％であつた。
実施例 ３
重粘土質土壌（粘土46.2％、シルト45.0％、細
砂2.9％、粗砂5.9％、組成Al2O321.6％、
Fe2O31.8％、SiO264.1％）風乾した後、風乾土壌
100重量部にクエン酸アルミニウムと塩化アルミ
ニウムの混合水溶液（Al2O30.4％、クエン酸2.6
％、Ｃ／Ｎ比20）25重量部を加え、実施例１と同
様の方法により21日間放置後耐水性団粒化率を測
定した結果18.5％であつた。一方、比較例として
クエン酸アルミニウム水溶液（Al2O30.4％、クエ
ン酸2.6％）を風乾重粘土質土壌100重量部に対
し、25重量部添加し、上記と同様の操作を行い、
耐水性団粒化率を測定した結果13.9％であつた。
実施例 ４
実施例３の風乾重粘土質土壌100重量部にシユ
ウ酸アルミニウム、シユウ酸鉄、シユウ酸アンモ
ニウムの混合水溶液（Al2O30.7％、Fe2O32.2％、
シユウ酸7.4％、Ｃ／Ｎ比6.7）30重量部を加え実
施例１と同様の方法により、14日間放置後耐水性
団粒化率を測定した結果23.5％であつた。一方、
比較例としてシユウ酸アンモニウムとシユウ酸鉄
の混合水溶液（Al2O30.7％、Fe2O32.1％、シユウ
酸4.6％）を風乾重粘土質土壌100重量部に対し30
重量部添加し、上記と同様の操作を行い、耐水性
団粒化率を測定した結果18.7％であつた。[Table] Example 2 30 parts by weight of a mixed aqueous solution of aluminum formate and ammonium formate (Al 2 O 3 1.01%, formic acid 6.2%, C/N ratio 15) was mixed with 100 parts by weight of the air-dried heavy clay soil of Example 1. However, the water-resistant agglomeration rate was measured after standing for 14 days by the same method as in Example 1, and the result was 25.1%. On the other hand, as a comparative example, 30 parts by weight of an aqueous aluminum formate solution (Al 2 O 3 1.0%, formic acid 5.7%) was added to 100 parts by weight of air-dried heavy clay soil, and the same operation as above was performed to determine the water-resistant agglomeration rate. The result of measuring 20.4
It was %. Example 3 Heavy clay soil (clay 46.2%, silt 45.0%, fine sand 2.9%, coarse sand 5.9%, composition Al 2 O 3 21.6%,
Fe 2 O 3 1.8%, SiO 2 64.1%) After air drying, air dry soil
100 parts by weight of a mixed aqueous solution of aluminum citrate and aluminum chloride (Al 2 O 3 0.4%, citric acid 2.6%)
%, C/N ratio 20) was added, and the water-resistant agglomeration rate was measured after standing for 21 days in the same manner as in Example 1 and found to be 18.5%. On the other hand, as a comparative example, 25 parts by weight of an aqueous aluminum citrate solution (0.4% Al 2 O 3 , 2.6% citric acid) was added to 100 parts by weight of air-dried heavy clay soil, and the same operation as above was performed.
The water-resistant agglomeration rate was measured and found to be 13.9%. Example 4 A mixed aqueous solution of aluminum oxalate, iron oxalate, and ammonium oxalate (Al 2 O 3 0.7%, Fe 2 O 3 2.2%, Fe 2 O 3 2.2%,
After adding 30 parts by weight of oxalic acid (7.4%, C/N ratio 6.7) and using the same method as in Example 1, the water-resistant agglomeration rate was measured after being left for 14 days and found to be 23.5%. on the other hand,
As a comparative example, a mixed aqueous solution of ammonium oxalate and iron oxalate (0.7% Al 2 O 3 , 2.1% Fe 2 O 3 , 4.6% oxalic acid) was mixed at 30% by weight for 100 parts by weight of air-dried heavy clay soil.
Part by weight was added, the same operation as above was carried out, and the water-resistant agglomeration rate was measured, and the result was 18.7%.