JP2005035828A

JP2005035828A - Granular slow-acting nitrogenous fertilizer

Info

Publication number: JP2005035828A
Application number: JP2003199211A
Authority: JP
Inventors: Takahiro Watanuki; 孝浩渡貫; Michihiro Inoguchi; 道浩井野口
Original assignee: Mitsubishi Chemical Agri Inc
Current assignee: Mitsubishi Chemical Agri Inc
Priority date: 2003-07-18
Filing date: 2003-07-18
Publication date: 2005-02-10
Anticipated expiration: 2023-07-18
Also published as: JP4487097B2

Abstract

<P>PROBLEM TO BE SOLVED: To provide a slow-acting nitrogenous fertilizer which is capable of controlling the elution speed of condensates of urea and aldehydes while maintaining its particle diameter constant, that elution speed has been conventionally mainly controlled by the particle diameter. <P>SOLUTION: The granular slow-acting nitrogenous fertilizer has a continuous phase containing the condensates of urea and the aldehydes and a dispersed phase containing an easily water-soluble substance, and in the fertilizer, the weight ratio of the continuous phase to the dispersed phase is 95/5 to 50/50. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】
本発明は、土壌中への肥料成分、とりわけ窒素成分の溶出速度が制御可能な粒状緩効性窒素肥料に関する。詳しくは、土壌中への肥料成分（窒素）の溶出が安定して行われ、被覆等を用いず、そして緩効性肥料の粒径が同等でも溶出速度の異なる粒状緩効性窒素肥料に存する。
【０００２】
【従来の技術】
農作物の栽培には、その生長段階に応じた肥料が必要であり、その必要時期に合わせるために従来から元肥、追肥等、作物の収穫までに数回の施肥を行ってきた。近年、農業が近代化され、また農業人口の減少に伴い、より手間の掛からない、施肥回数が少なくて済む肥料の開発が求められ、肥料成分の溶出を作物の養分要求特性に適合させるように制御すべく様々な肥料が開発された。
【０００３】
例えば速効性窒素肥料の施肥に際しては、作物に対する高窒素濃度障害の回避や窒素肥料の利用率向上の為に、必要量を数回に分けて施肥が行われている。
一方で、緩効性窒素肥料、例えば尿素―イソブチルアルデヒド縮合物（イソブチリデン２尿素。以下、「ＩＢＤＵ」と記すことがある。）に代表される尿素−アルデヒド類縮合物は、水への溶解度が低いために土壌中では徐々に分解することを利用したものであり、必要量を一度に施肥することが可能であり施肥作業が省力化でき、また溶脱・流亡が生じ難いので作物の利用効率が高いという利点がある。またこの様な緩効性肥料においては、その溶解速度が粒状緩効性肥料の表面積に比例するので、比表面積を調整すべく肥料の粒径を変え、施肥条件に見合う溶解速度を有する粒状緩効性肥料とすることがなされていた。
【０００４】
近年では、窒素、燐酸、加里等の各種肥料成分を含有する肥料を施肥前にブレンドし用いる、いわゆるバルクブレンド肥料（以下「ＢＢ肥料」と記すことがある。）が普及してきている。このような肥料では、肥料成分の偏りの原因となる分級、つまり保存容器中や施肥機械中に於いて、大きい粒は上に、小さい粒は下に集まることを防止するため、各種肥料の粒径をそろえることが重要となっている。また、側条施肥機やブロードキャスター等の各種施肥機を用いた機械施肥方法も、省力化の要望に応え盛んになってきている。このような機械を用いた施肥の際には、一つの機械で扱える粒状肥料の粒子径が限られている。よってこの様な施肥方法に用いる場合には、窒素を主成分とする肥料に於いても、窒素成分以外の、燐酸成分や加里成分含有粒状肥料と粒子径をそろえる必要がある。
【０００５】
しかし従来の粒状緩効性肥料、とりわけ粒状緩効性窒素肥料においては、粒子径を調整することによって溶出速度の異なる粒状緩効性窒素肥料としているので、その使用が限られてしまうという問題が生じてきた。更にＢＢ肥料や機械施肥方法に用いる肥料においては、先述の通り、粒度分布が揃った、且つ粒硬度の比較的高い粒状肥料を用いる為に、従来からの緩効性窒素肥料、例えば尿素―アルデヒド類縮合物等であっても、粒子径が小さく、そして比較的大きな粒子径を有するものを製造することが困難である上に、硬度が低いので、ＢＢ肥料や機械施肥方法に供する窒素成分肥料としては問題があった。
【０００６】
これに対し、尿素―アルデヒド類縮合物を造粒した硬度の高い緩効性窒素肥料の製造方法等が提案されている（特許文献１参照）。この方法によって平均粒径が２〜４ｍｍの緩効性窒素肥料を得ることが出来、ＢＢ肥料や機械施肥に用いうるものが提案されている。
【０００７】
【特許文献１】特開平２−２８９４７９号公報
【０００８】
【発明が解決しようとする課題】
しかしこのような緩効性窒素肥料を用いたＢＢ肥料等に於いても、その平均粒径は一般的に２〜４ｍｍ程度であり、この限られた粒径の範囲内では、肥料成分（窒素）の溶出速度パターンが極めて限られており、多種多様な植物の栽培期間に適合する溶出パターンを有する肥料とはなりえないという問題があった。例えば重要な農産物である２発施肥体系（基肥と穂肥）での水稲栽培や秋冬作野菜栽培における窒素成分の施肥に際しては、２〜４ｍｍの粒径では肥効期間が長すぎ、ＢＢ肥料への適応がなされていない等の問題があった。この様な状況下、緩効性窒素肥料、中でも溶出パターンが一般に「Ｌ型」と称される緩効性窒素肥料において、２〜４ｍｍの粒径でかつ肥効期間が従来よりも短い緩効性窒素肥料が望まれていた。
【０００９】
【課題を解決するための手段】
そこで本発明者らは、粒子径を調整せずに肥料成分の溶出速度を調整する方法、とりわけ窒素成分の溶出速度を調整する方法について鋭意検討した。本発明者らは、水への溶解度が低い緩効性窒素肥料において、その表面積と土壌中への窒素成分の溶出速度が密接な関係にあることに着目し、そして緩効性肥料粒子に於いて、その粒子内部を多孔質化して比表面積を調整することによって窒素成分の溶解速度を調整出来ることを見出した。
【００１０】
またこの様な多孔質緩効性粒状肥料を連続相とし、そして分散相に易水溶性物質、具体的には溶解度（２５℃の飽和水溶液１００ｇ中の溶質重量）が１０ｇ以上のものである易水溶性物質を用い、これらを特定の比率で含有させた粒状窒素肥料が、その粒径を変更せずとも窒素成分の溶出速度を極めて広い範囲で調整可能な粒状緩効性窒素肥料となることを見出し、本発明を完成させた。
【００１１】
即ち本発明は、尿素−アルデヒド類縮合物を含む連続相と、易水溶性物質を含む分散相とを有し、その重量比が９５：５〜５０：５０である粒状緩効性窒素肥料に存する。
【００１２】
【発明の実施の形態】
以下、本発明を詳細に説明する。
本発明の粒状緩効性肥料においては、尿素−アルデヒド類縮合物を連続相として用いる。この尿素−アルデヒド類縮合物は、尿素とアルデヒド類を脱水縮合反応させて得られたものであり、その製造方法は任意である。
【００１３】
この脱水縮合反応に用いるアルデヒド類は任意のものを使用することが出来る。具体的には例えば、イソブチルアルデヒド、クロトンアルデヒド、アセトアルデヒド、ホルムアルデヒド等が挙げられる。またこの反応に用いる尿素としては、その形状は任意であり、固体、液体（溶融液）等のいずれでもよい。
本発明で用いる尿素−アルデヒド類縮合物としては例えば、尿素−イソブチルアルデヒド縮合物（ＩＢＤＵ）、尿素−ホルムアルデヒド縮合物（ウレアホルム。以下、「ＵＦ」と記すことがある。）、及び尿素−クロトンアルデヒド縮合物（クロトニリデン２尿素。以下「ＣＤＵ」と記すことがある。）等が挙げられる。例えばＵＦ等は、その縮合度を調整するという工業的に困難な手法を取らずとも、本発明によって簡便な方法で窒素成分の溶出速度を調整することが出来る。中でも本発明においては、尿素とアルデヒド類とを縮合して得られた尿素―アルデヒド類縮合物が、複数の縮合度を有するものからなる際に、同一縮合度の尿素―アルデヒド類縮合物を７０重量％以上含有することが、緩効性窒素肥料としての溶出曲線が安定するので好ましく、中でも８０重量％以上、特に９０重量％以上含有するものであることが好ましい。具体的には、その製造過程で様々な縮合物を生じる為に同一縮合度を有する縮合物の含有量が５０重量％程度のＵＦに比べて、ＩＢＤＵやＣＤＵを用いることによって、同一縮合度を有する縮合物を７０重量％以上含有する縮合物が容易に得られるので好ましい。
【００１４】
本発明においては、例えば尿素−アルデヒド類縮合物を粒状物として用い、この粒状の尿素−アルデヒド類縮合物と後述する易水溶性物質とを造粒等の方法によって本発明の粒状緩効性窒素肥料を製造することが出来る。この際に用いる尿素−アルデヒド類縮合物の粒径は、製造する本発明の粒状緩効性肥料の粒径以下であればよい。中でも、製造方法における造粒性や尿素−アルデヒド類縮合物が溶解した後の空洞構造に寄与する易水溶性物質の分散性等を考慮すると、本発明の粒状緩効性肥料の直径に対して１／４以下、中でも１／６以下、特に１／８以下であることが好ましい。
【００１５】
本発明に用いる易水溶性物質としては、従来公知のものを使用することができるが、易水溶性肥料は粒状緩効性窒素肥料の肥料成分を高く出来る点で好ましく、中でも速効性窒素肥料は粒状緩効性肥料が窒素単肥となることからＢＢ肥料原料への適用性が優れており、更に好ましい。
本発明における易水溶性物質とは水への溶解度が高いものであり、具体的には溶解度（２５℃の飽和水溶液１００ｇ中の溶質重量）が１０ｇ以上のものである。具体的には例えば、尿素（５４．８）、硫酸アンモニウム（４３．３）、塩化アンモニウム（２８．２）、硝酸アンモニウム（６８．２）、硝酸ナトリウム（４７．９）、リン酸二アンモニウム（４１．０）、リン酸一アンモニウム（２９．４）、リン酸水素二カリウム（６２．０）、塩化カリウム（２６．４）、硫酸カリウム（１０．７５）、塩化マグネシウム（３５．５）、硫酸マグネシウム（２６．７）、塩化カルシウム（４５．３）等が挙げられる（かっこ内の数字は溶解度を示す）。前述の通り、これらの中でも粒状緩効性肥料が窒素単肥となりうることから、速効性窒素肥料が好ましく、更に化合物中における窒素成分が高く、入手が容易である等の理由から尿素が好ましい。
【００１６】
本発明における易水溶性物質の含有量は任意である。一般的には先述の緩効性窒素肥料である尿素―アルデヒド類縮合物との重量比（尿素―アルデヒド類縮合物：易水溶性物質）が、９５：５〜５０：５０、中でも９０：１０〜６０：４０、更には９０：１０〜７０：３０、特に９０：１０〜８０：２０であることが好ましい。この比が９５：５を下回って易水溶性物質の含有量が少ないと、造粒物内部の空洞化作用が不十分となり従来の尿素−アルデヒド類縮合物のみを造粒した場合と肥効期間の差が認められず、逆に５０：５０を超えて速効性窒素肥料の含有量が多いと、土壌中への窒素成分の溶出速度が速くなるために緩効性肥料としての効果が不十分となる場合がある。
【００１７】
本発明の粒状緩効性窒素肥料は、このような易水溶性物質が溶出した後の連続相、つまり緩効性窒素の比表面積が従来のものと比べて非常に大きいことを特徴とする。この連続相の比表面積は、施肥対象の植物等によって適宜調整すればよく、その調整方法は後述する本発明の粒状緩効性窒素肥料の製造方法において、易水溶性物質との量比によって決定することが出来る。
【００１８】
尚、本発明の粒状緩効性窒素肥料においては、その他の肥料成分を含む肥料粒とブレンドし、バルクブレンド肥料として使用してもよい。用いる肥料粒としては従来公知の任意ものを使用でき、例えば硫安、塩安、硝安、石灰窒素、過燐酸石灰、重過石、重焼燐、塩加、硫加等の単肥の他に、Ｎ、Ｐ_２Ｏ_５、Ｋ_２Ｏ等の２成分以上からなる燐安、化成肥料、およびこれらを２種以上複合したバルクブレンド肥料が挙げられる。
【００１９】
本発明の粒状緩効性窒素肥料の製造方法は、例えば先述の緩効性窒素肥料である尿素―アルデヒド類縮合物と、易水溶性物質とを造粒して製造することができる。造粒に際しては造粒液等を用いてもよく、例えば水、易水溶性物質水溶液、メチロール尿素液、及び尿素―アルデヒド類縮合物を水に分散させたもの等が挙げられる。中でも、易水溶性物質水溶液は、造粒物内部の空洞化現象に寄与する易水溶性物質を均一に分散させるという理由から好ましい。一方、メチロール尿素液を用いた場合は、前記の（特許文献１）に示されたように、粒子硬度が非常に高くなり、ＢＢ肥料や機械施肥法に適した物性が得られる点で好ましい。
【００２０】
本発明の粒状緩効性窒素肥料の製造に用いる造粒装置としては、従来公知の粒状肥料製造技術のうち、任意のものを適宜選択して採用すればよい。例えば造粒容器自体が回転するタイプの皿型造粒機やドラム型造粒機、造粒容器内部の撹拌羽根が高速回転するタイプの撹拌（混合）型造粒装置等が挙げられる。本発明の主原料である尿素−アルデヒド縮合物は、一般の化成肥料に比べ比重が軽く、撥水性も高い故に造粒性が悪い。従って、上記装置の中でも、造粒能力が高い（粒にかかる圧縮応力が高い）という理由から、撹拌（混合）型の造粒装置を用いることが好ましい。
【００２１】
本発明の粒状緩効性窒素肥料の製造方法においては、この様な造粒装置を用い、例えば造粒装置により粒状緩効性窒素肥料の核となる粒子を転動させ、これに造粒液と緩効性肥料及び易水溶性物質を交互或いは同時に添加することを続け、粒を必要な粒径まで成長（造粒）させればよい。粒径の調節は、造粒液の添加量、添加速度、造粒機の機械的条件、及び造粒時間等を適宜調節する等の従来公知の技術により行えばよい。
【００２２】
緩効性肥料粉体と易水溶性物質粉体とを予め混合しておき、その粉体を造粒する方法や、造粒時にこの両方の粉体を別々に添加する方法等も可能である。その際、本発明の粒状緩効性窒素肥料内部の空洞化に寄与する易水溶性物質の分散性を考慮すると、両粉体を同時に添加することが好ましい。また、造粒液の添加方法も任意であるが、造粒物が十分に転動している部分になるべく均一に添加すれば、製品粒径の取得率が向上するので好ましい。また造粒操作終了後、所望の粒径に満たない小粒径品が生じた際には、これを次の造粒操作における粒状緩効性窒素肥料の核となる小粒子として用いることが好ましい。
【００２３】
そして必要に応じて、造粒後に得られた粒状緩効性窒素肥料を乾燥してもよい。乾燥温度は、粒状緩効性窒素肥料中の尿素―アルデヒド類縮合物や、尿素などの易水溶性物質が分解しない範囲内で行うことが好ましく、具体的には室温〜１２０℃、中でも４０〜１２０℃、特に６０〜１００℃の範囲内にて行うことが好ましい。例えば造粒液の一部としてメチロール尿素水溶液を用いて造粒した際には、このメチロール尿素が酸触媒の作用でメチレン化反応を起こし、尿素樹脂接着剤として物性維持に寄与するよう、６０〜１２０℃、特に８０〜１００℃の温度範囲内で乾燥することが好ましい。
【００２４】
本発明の粒状緩効性窒素肥料の粒子径は任意であり、使用場面に合わせて適宜調整すればよい。一般的には０．５〜１５ｍｍ、中でも１〜１０ｍｍ、更には２〜６ｍｍが好ましく、特にＢＢ肥料や機械施肥用の粒状緩効性窒素肥料とするに際しては２〜４ｍｍであることが好ましい。また本発明の粒状緩効性窒素肥料の形状も任意であるが、真球性が高い程、例えばバルクブレンド肥料とした際や機械施肥用肥料とした際の取扱性が良好となるので好ましい。
【００２５】
こうして得られた本発明の粒状緩効性窒素肥料は、尿素−アルデヒド類縮合物（連続相）の隙間に易水溶性物質（分散相）を配した構造となり、このような造粒物が土中に施肥されると、土壌中の水分により、まず易水溶性物質が速やかに土中へ溶出し、粒状緩効性窒素肥料内部が空洞化する。そして内部が空洞化すると、尿素−アルデヒド類縮合物の表面積が増大し、その溶出速度も同一粒径の尿素−アルデヒド類縮合物単独造粒物のそれに比べて増大する。即ち、造粒物本来の粒径から想定される以上の溶出速度が達成され、同一の粒径でありながら、異なる溶出速度を創出することが出来る。
【００２６】
本発明の粒状緩効性窒素肥料の用途は特に限定されるものではなく、作物の養分要求特性に合わせて適宜選択される。例えば、従来の尿素−アルデヒド類縮合物単独造粒物（粒径２〜４ｍｍ）では肥効期間が長すぎて適用できなかった、２発施肥体系（基肥と穂肥）での水稲栽培や秋冬作野菜栽培における窒素成分の施肥に際して使用可能となり、緩効性窒素肥料の適用範囲が大きく広がった。
【００２７】
【実施例】
以下に実施例を示し、本発明をより具体的に説明するが、本発明はその趣旨を超えない限り、以下の実施例に限定されるものではない。
実施例１、２
粒状緩効性肥料の製造：
核となる小粒子にＩＢＤＵ小粒品（粒径０．７〜２．５ｍｍ）を、まぶし粉としてＩＢＤＵ粉体（粒径０．５ｍｍ以下）を表１の通り計量し準備した。易水溶性物質としては尿素を用い、粉砕品（粒径０．５ｍｍ以下）を上述のＩＢＤＵ粉体と混合して使用した。
【００２８】
脱塩水３６５．６ｇに尿素３９４．８ｇ及びホウ砂９．９ｇを添加し、５０℃に加温してこれにパラホルムアルデヒド（８６％濃度）２２９．７ｇを添加し、６０分間撹拌し、メチロール尿素水溶液を調整した。このメチロール尿素水溶液に、メチレン化触媒として５０％クエン酸を造粒操作の使用直前に１９．４ｇ／１０００ｇの割合で添加し、造粒液とした。
【００２９】
撹拌型造粒機（大和加工機製、ＮＧ−３５０型）に核用のＩＢＤＵ小粒品を７８０ｇ入れ、撹拌羽根の回転数が３００±５０ｒｐｍとなるように撹拌しながら、表１に示す量の造粒液とＩＢＤＵ粉体と尿素粉体の混合物を徐々に加えながら、約１０分間造粒操作を行った。得られた造粒物を篩い分けし、２．３６〜４ｍｍのものを更に１００℃で１時間乾燥し、以下の水中溶出試験に供試した。
水中溶出試験：
製造した粒状緩効性窒素肥料２００ｍｇと海砂（１５〜２０ｍｅｓｈ）２０ｇを混合し、不織布の袋に詰め、溶出用パックとした。２００ｍｌ容のスチロール製容器に脱塩水２００ｍｌと溶出用パックを入れ、蓋をした後２５℃の恒温器内に静置した。所定期間経過後、容器内を軽く撹拌し、溶出液の窒素含量を測定した。溶出液中の窒素含量と予め求めておいた仕込み窒素量から、溶出率を算出した。残りの溶出液は廃棄し、新たに脱塩水２００ｍｌを加え、再度２５℃の恒温器内に静置した。以上の操作を積算溶出率が８０％を越えるまで繰り返した。造粒物の特性値を表２に示す。また水中溶出試験の結果を図１〜３に示す。
【００３０】
比較例１
尿素を用いなかったこと以外は、実施例１と同様に、表１に記載の量にて肥料を造粒し、評価した。造粒物の特性値を表２に示す。また水中溶出試験の結果を図１に示す。
【００３１】
比較例２
比較例１と粒状尿素を窒素比で９０：１０となるように混合（バルクブレンド）し、比較例２を得た。これを実施例１と同様に評価した。混合物の水中溶出試験の結果を図２に示す。
【００３２】
比較例３
比較例１と粒状尿素を窒素比で７０：３０となるように混合（バルクブレンド）し、比較例３を得た。これを実施例１と同様に評価した。混合物の水中溶出試験の結果を図３に示す。
【００３３】
【表１】

【００３４】
【表２】

【００３５】
図１の実施例１、２と比較例１との比較から明らかなように、易水溶性物質である尿素を緩効性窒素肥料ＩＢＤＵと共に造粒した実施例１、２においては、ＩＢＤＵのみを造粒した比較例１に比べて、同一粒径にも関わらず明らかに溶出速度が大きくなっていることが判る。
【００３６】
更に、図２の実施例１と比較例２との比較及び図３の実施例２と比較例３との比較から明らかなように、易水溶性物質である尿素をＩＢＤＵと共に造粒した実施例１及び２は、比較例２及び３と同一粒径かつ同一尿素比率であるにも関わらず、明らかに溶出速度が大きくなっていることが判る。
以上の通り、緩効性窒素肥料中に易水溶性物質を分散させた場合は、それらを単に配合した場合よりも、明らかに大きな溶出速度を示した。このことは、水中投入後速やかに易水溶性物質が溶出し、緩効性窒素肥料内部が空洞化し（内部表面積が増大し）、同一粒径にもかかわらず緩効性窒素肥料の溶出速度が大きくなったことを示している。即ち、従来困難であった同一粒径での緩効性窒素肥料の溶出速度コントロールが可能となった。
【００３７】
【発明の効果】
本発明の粒状緩効性窒素肥料によって、施肥後速やかに易水溶性物質が土中へ溶出することで施肥初期の土中への窒素溶出量増加させ、且つ易水溶性物質の溶出後に残った緩効性窒素肥料粒子は、従来の同一粒径の易水溶性物質を含まない粒状緩効性窒素肥料と比較すると、内部が空洞化して表面積が増大しているので、土中への窒素成分の溶出速度が向上し、今までにない溶出パターンの粒状緩効性窒素肥料を提供することが出来る。
【図面の簡単な説明】
【図１】実施例及び比較例における粒状肥料の溶出パターンを示した図である。
【図２】実施例及び比較例における粒状肥料の溶出パターンを示した図である。
【図３】実施例及び比較例における粒状肥料の溶出パターンを示した図である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a granular slow release nitrogen fertilizer capable of controlling the elution rate of fertilizer components, particularly nitrogen components, into soil. Specifically, fertilizer components (nitrogen) are leached stably in the soil, and there is no covering, etc., and there is a granular slow-release nitrogen fertilizer with different release rates even if the particle size of the slow-release fertilizer is the same. .
[0002]
[Prior art]
Fertilizer according to the growth stage is necessary for cultivation of agricultural crops, and in order to match the required time, fertilizer has been applied several times before harvesting crops such as raw fertilizer and topdressing. In recent years, with the modernization of agriculture and the decline in the agricultural population, there is a need for the development of fertilizers that require less time and less fertilization, so that the elution of fertilizer components can be adapted to the nutrient requirements of crops. Various fertilizers have been developed to control.
[0003]
For example, when fertilizing fast-acting nitrogen fertilizer, fertilization is carried out by dividing the required amount into several times in order to avoid high nitrogen concentration damage to crops and improve the utilization rate of nitrogen fertilizer.
On the other hand, slow-acting nitrogen fertilizers, such as urea-isobutyraldehyde condensates (isobutylidene diurea, hereinafter sometimes referred to as “IBDU”), have a solubility in water. Because it is low, it uses the gradual decomposition in the soil, it is possible to fertilize the required amount at once, save labor for fertilization work, and it is difficult to cause leaching and runoff, so the efficiency of crop use is high There is an advantage of high. In such a slow-release fertilizer, the dissolution rate is proportional to the surface area of the granular slow-release fertilizer. Therefore, the particle size of the fertilizer is changed to adjust the specific surface area, and the granular slow-release fertilizer has a dissolution rate that matches the fertilization conditions. It was supposed to be an effective fertilizer.
[0004]
In recent years, so-called bulk blend fertilizers (hereinafter sometimes referred to as “BB fertilizers”) in which fertilizers containing various fertilizer components such as nitrogen, phosphoric acid, and potassium are blended before fertilization are widely used. In such a fertilizer, in order to prevent the fertilizer components from being biased, that is, in the storage container or fertilizer machine, large grains are prevented from collecting on the top and small grains on the bottom. It is important to align the diameters. In addition, mechanical fertilization methods using various fertilizers such as a side fertilizer and a broadcaster have been actively responding to demands for labor saving. When fertilizing using such a machine, the particle size of granular fertilizer that can be handled by one machine is limited. Therefore, when using for such a fertilization method, it is necessary to arrange | equalize the particle diameter with the fertilizer which contains a phosphoric acid component and a potassium component other than a nitrogen component also in the fertilizer which has nitrogen as a main component.
[0005]
However, conventional granular slow-release fertilizers, especially granular slow-release nitrogen fertilizers, have a problem that their use is limited because the granular slow-release nitrogen fertilizer has different elution rates by adjusting the particle size. It has occurred. Further, in the fertilizer used for the BB fertilizer and the mechanical fertilization method, as described above, since a granular fertilizer having a uniform particle size distribution and a relatively high grain hardness is used, a conventional slow-release nitrogen fertilizer such as urea-aldehyde is used. Nitrogen component fertilizers for use in BB fertilizers and mechanical fertilization methods because it is difficult to produce a condensate or the like having a small particle size and a relatively large particle size and low hardness There was a problem.
[0006]
On the other hand, a method for producing a slow-release nitrogen fertilizer having high hardness obtained by granulating a urea-aldehyde condensate has been proposed (see Patent Document 1). By this method, a slow-acting nitrogen fertilizer having an average particle diameter of 2 to 4 mm can be obtained, and what can be used for BB fertilizer and mechanical fertilization has been proposed.
[0007]
[Patent Document 1] Japanese Patent Application Laid-Open No. 2-289479
[Problems to be solved by the invention]
However, even in BB fertilizers using such slow-release nitrogen fertilizers, the average particle size is generally about 2 to 4 mm, and within this limited particle size range, fertilizer components (nitrogen) ) Is very limited, and there is a problem that it cannot be a fertilizer having an elution pattern suitable for a variety of plant cultivation periods. For example, when fertilizing nitrogen components in paddy rice cultivation and autumn / winter cropping cultivation in two fertilization systems (basic fertilizer and pantilizer), which are important agricultural products, the fertilization period is too long with a particle size of 2 to 4 mm, and to BB fertilizer There were problems such as not being adapted. Under such circumstances, slow-release nitrogen fertilizers, particularly slow-release nitrogen fertilizers whose elution pattern is generally called “L-type”, have a particle size of 2 to 4 mm and a short duration of fertilization. Nitrogen fertilizer was desired.
[0009]
[Means for Solving the Problems]
Therefore, the present inventors diligently studied a method for adjusting the elution rate of the fertilizer component without adjusting the particle diameter, particularly a method for adjusting the elution rate of the nitrogen component. In the slow-release nitrogenous fertilizer having low solubility in water, the present inventors paid attention to the fact that the surface area and the dissolution rate of the nitrogen component into the soil are closely related, and in the slow-release fertilizer particles. It was found that the dissolution rate of the nitrogen component can be adjusted by making the inside of the particles porous and adjusting the specific surface area.
[0010]
Further, such a porous slow-release granular fertilizer is used as a continuous phase, and an easily water-soluble substance in the dispersed phase, specifically, a solubility (a solute weight in 100 g of a saturated aqueous solution at 25 ° C.) is 10 g or more. Granular nitrogen fertilizers containing water-soluble substances and containing them in specific ratios should be granular slow-release nitrogen fertilizers that can adjust the elution rate of nitrogen components in a very wide range without changing the particle size. The present invention was completed.
[0011]
That is, the present invention provides a granular slow-release nitrogenous fertilizer having a continuous phase containing a urea-aldehyde condensate and a dispersed phase containing a readily water-soluble substance and having a weight ratio of 95: 5 to 50:50. Exist.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail.
In the granular slow-release fertilizer of the present invention, a urea-aldehyde condensate is used as a continuous phase. This urea-aldehyde condensate is obtained by subjecting urea and aldehydes to a dehydration condensation reaction, and its production method is arbitrary.
[0013]
Any aldehyde can be used for the dehydration condensation reaction. Specific examples include isobutyraldehyde, crotonaldehyde, acetaldehyde, formaldehyde and the like. The urea used in this reaction may have any shape and may be solid, liquid (melt), or the like.
Examples of the urea-aldehyde condensate used in the present invention include urea-isobutyraldehyde condensate (IBDU), urea-formaldehyde condensate (ureaform, hereinafter sometimes referred to as “UF”), and urea-crotonaldehyde. And a condensate (crotonylidene diurea, hereinafter sometimes referred to as “CDU”). For example, UF and the like can adjust the elution rate of the nitrogen component by a simple method according to the present invention without taking an industrially difficult method of adjusting the degree of condensation. In particular, in the present invention, when the urea-aldehyde condensate obtained by condensing urea and aldehydes has a plurality of condensation degrees, a urea-aldehyde condensate having the same condensation degree is 70%. It is preferable to contain it in an amount of not less than 80% by weight because the dissolution curve as a slow-release nitrogenous fertilizer is stable. Specifically, in order to produce various condensates in the production process, the same degree of condensation can be obtained by using IBDU or CDU compared to UF having the same degree of condensate content of about 50% by weight. This is preferable because a condensate containing 70% by weight or more of the condensate is easily obtained.
[0014]
In the present invention, for example, a urea-aldehyde condensate is used as a granular material, and the granular urea-aldehyde condensate and a readily water-soluble substance to be described later are granulated or the like to form the granular slow-release nitrogen of the present invention. Fertilizer can be manufactured. The particle size of the urea-aldehyde condensate used in this case may be equal to or smaller than the particle size of the granular slow-release fertilizer of the present invention to be produced. Among them, considering the granulation property in the production method and the dispersibility of the readily water-soluble substance that contributes to the cavity structure after the urea-aldehyde condensate is dissolved, the diameter of the granular slow-release fertilizer of the present invention It is preferably 1/4 or less, particularly 1/6 or less, particularly 1/8 or less.
[0015]
As the readily water-soluble substance used in the present invention, conventionally known substances can be used, but the easily water-soluble fertilizer is preferable in that the fertilizer component of the granular slow-release nitrogen fertilizer can be increased, and among these, the fast-acting nitrogen fertilizer is Since the granular slow-release fertilizer becomes nitrogen simple fertilizer, the applicability to the BB fertilizer raw material is excellent, and more preferable.
The easily water-soluble substance in the present invention has high water solubility, and specifically has a solubility (solute weight in 100 g of a saturated aqueous solution at 25 ° C.) of 10 g or more. Specifically, for example, urea (54.8), ammonium sulfate (43.3), ammonium chloride (28.2), ammonium nitrate (68.2), sodium nitrate (47.9), diammonium phosphate (41. 0), monoammonium phosphate (29.4), dipotassium hydrogen phosphate (62.0), potassium chloride (26.4), potassium sulfate (10.75), magnesium chloride (35.5), magnesium sulfate (26.7), calcium chloride (45.3), etc. (numbers in parentheses indicate solubility). As described above, among these, the granular slow-release fertilizer can be a simple nitrogen fertilizer, so that a fast-acting nitrogen fertilizer is preferable, and urea is preferable because it has a high nitrogen component in the compound and is easily available.
[0016]
The content of the easily water-soluble substance in the present invention is arbitrary. In general, the weight ratio of the above-mentioned slow-acting nitrogen fertilizer urea-aldehyde condensate (urea-aldehyde condensate: water-soluble substance) is 95: 5 to 50:50, especially 90:10. 60:40, more preferably 90:10 to 70:30, and particularly preferably 90:10 to 80:20. When this ratio is less than 95: 5 and the content of the easily water-soluble substance is small, the cavitation action inside the granulated product becomes insufficient, and the conventional urea-aldehyde condensate is granulated and the fertilization period On the contrary, if the content of fast-acting nitrogen fertilizer exceeds 50:50 and the content of fast-acting nitrogen fertilizer is large, the elution rate of nitrogen components into the soil increases, so the effect as a slow-acting fertilizer is insufficient. It may become.
[0017]
The granular slow-release nitrogen fertilizer of the present invention is characterized in that the specific surface area of the continuous phase after elution of such a readily water-soluble substance, that is, slow-release nitrogen is much larger than that of the conventional one. The specific surface area of the continuous phase may be adjusted as appropriate depending on the plant to be fertilized, and the adjustment method is determined by the ratio of the water-soluble substance to the water-soluble substance in the granular slow-release nitrogen fertilizer production method of the present invention described later. I can do it.
[0018]
The granular slow-release nitrogen fertilizer of the present invention may be blended with fertilizer grains containing other fertilizer components and used as a bulk blend fertilizer. As the fertilizer grains to be used, any conventionally known fertilizer grains can be used. For example, N, in addition to simple fertilizers such as ammonium sulfate, ammonium sulfate, ammonium nitrate, lime nitrogen, percalcium lime, bitumen, heavy calcined phosphorus, salted, sulfurized, etc. , P ₂ O ₅ , P ₂ O ₅ , K ₂ O and other phosphorous ammonium, chemical fertilizers, and bulk blend fertilizers in which two or more of these are combined.
[0019]
The method for producing a granular slow-release nitrogenous fertilizer of the present invention can be produced, for example, by granulating a urea-aldehyde condensate, which is the above-mentioned slow-release nitrogenous fertilizer, and a readily water-soluble substance. For granulation, a granulation liquid or the like may be used, and examples thereof include water, a water-soluble substance aqueous solution, a methylol urea liquid, and a urea-aldehyde condensate dispersed in water. Among these, an easily water-soluble substance aqueous solution is preferable because the easily water-soluble substance contributing to the cavitation phenomenon inside the granulated product is uniformly dispersed. On the other hand, when a methylol urea solution is used, as shown in the above (Patent Document 1), the particle hardness is very high, which is preferable in that physical properties suitable for BB fertilizer and mechanical fertilization are obtained.
[0020]
What is necessary is just to select suitably and arbitrarily employ | adopt among the conventionally well-known granular fertilizer manufacturing techniques as a granulation apparatus used for manufacture of the granular slow release nitrogen fertilizer of this invention. For example, a dish type granulator or drum type granulator of the type in which the granulation container itself rotates, an agitation (mixing) type granulator of the type in which the stirring blade inside the granulation container rotates at high speed, and the like can be mentioned. The urea-aldehyde condensate, which is the main raw material of the present invention, has a low specific gravity and high water repellency compared to general chemical fertilizers, and therefore has poor granulation properties. Therefore, among the above apparatuses, it is preferable to use a stirring (mixing) type granulating apparatus because of its high granulating ability (high compressive stress applied to the grains).
[0021]
In the method for producing granular slow-release nitrogenous fertilizer of the present invention, such a granulator is used, for example, the particles serving as the core of the granular slow-release nitrogenous fertilizer are rolled by the granulator, and the granulated liquid is used for this. And the slow-release fertilizer and the easily water-soluble substance may be added alternately or simultaneously to grow (granulate) the grains to the required particle size. The particle diameter may be adjusted by a conventionally known technique such as appropriately adjusting the addition amount of the granulation liquid, the addition speed, the mechanical conditions of the granulator, the granulation time, and the like.
[0022]
A slow-release fertilizer powder and a readily water-soluble substance powder can be mixed in advance, and the powder can be granulated, or both powders can be added separately during granulation. . At that time, it is preferable to add both powders at the same time, considering the dispersibility of the easily water-soluble substance that contributes to the hollow formation of the granular slow-release nitrogen fertilizer of the present invention. The granulating liquid may be added by any method, but it is preferable to add the granulated product as uniformly as possible to the part where the granulated product is sufficiently rolled, because the acquisition rate of the product particle size is improved. Further, when a product having a small particle size less than the desired particle size is produced after completion of the granulation operation, it is preferably used as a small particle that becomes the core of the granular slow-release nitrogen fertilizer in the next granulation operation. .
[0023]
And as needed, you may dry the granular slow release nitrogen fertilizer obtained after granulation. The drying temperature is preferably within a range in which the urea-aldehyde condensate in the granular slow-release nitrogenous fertilizer and easily water-soluble substances such as urea are not decomposed, specifically room temperature to 120 ° C., particularly 40 to It is preferable to carry out within a range of 120 ° C., particularly 60 to 100 ° C. For example, when granulation is performed using a methylol urea aqueous solution as a part of the granulation liquid, the methylol urea causes a methyleneation reaction by the action of an acid catalyst, and contributes to maintaining physical properties as a urea resin adhesive. It is preferable to dry within a temperature range of 120 ° C., particularly 80 to 100 ° C.
[0024]
The particle diameter of the granular slow-release nitrogenous fertilizer of the present invention is arbitrary, and may be appropriately adjusted according to the usage scene. In general, 0.5 to 15 mm, particularly 1 to 10 mm, and more preferably 2 to 6 mm are preferable. In particular, when the granular slow-release nitrogen fertilizer is used for BB fertilizer or mechanical fertilization, it is preferably 2 to 4 mm. The shape of the granular slow-release nitrogenous fertilizer of the present invention is also arbitrary, but the higher the sphericity, the better the handleability when using, for example, a bulk blend fertilizer or a mechanical fertilizer.
[0025]
The granular slow-release nitrogenous fertilizer of the present invention thus obtained has a structure in which an easily water-soluble substance (dispersed phase) is arranged in the gap between the urea-aldehyde condensates (continuous phase), and such a granulated material is soiled. When fertilized inside, the water-soluble substance is first quickly eluted into the soil by moisture in the soil, and the inside of the granular slow-release nitrogen fertilizer is hollowed out. When the inside becomes hollow, the surface area of the urea-aldehyde condensate increases, and the elution rate also increases as compared with that of the single granule of urea-aldehyde condensate having the same particle size. That is, an elution rate higher than expected from the original particle size of the granulated product is achieved, and different elution rates can be created while maintaining the same particle size.
[0026]
The use of the granular slow-release nitrogen fertilizer of the present invention is not particularly limited, and is appropriately selected according to the nutrient requirement characteristics of the crop. For example, the conventional urea-aldehyde condensate single granulated product (particle size 2 to 4 mm) was too long to be applied and could not be applied. It became usable when fertilizing nitrogen components in vegetable cultivation, and the range of application of slow-release nitrogen fertilizer was greatly expanded.
[0027]
【Example】
EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples as long as the gist thereof is not exceeded.
Examples 1 and 2
Production of granular slow-release fertilizer:
As shown in Table 1, IBDU small particles (particle size: 0.7 to 2.5 mm) and IBDU powder (particle size: 0.5 mm or less) were measured and prepared as the dust particles. Urea was used as the easily water-soluble substance, and a pulverized product (particle diameter of 0.5 mm or less) was mixed with the above-mentioned IBDU powder.
[0028]
Add 394.8 g of urea and 9.9 g of borax to 365.6 g of demineralized water, warm to 50 ° C., add 229.7 g of paraformaldehyde (86% concentration), stir for 60 minutes, and then methylol urea. An aqueous solution was prepared. To this methylol urea aqueous solution, 50% citric acid as a methyleneation catalyst was added at a ratio of 19.4 g / 1000 g immediately before the use of the granulating operation to prepare a granulating liquid.
[0029]
780g of core IBDU granules are put into an agitation type granulator (manufactured by Daiwa Processing Machine, Model NG-350), and the agitation of the amount shown in Table 1 is carried out while stirring so that the number of revolutions of the agitation blade is 300 ± 50 rpm. The granulation operation was performed for about 10 minutes while gradually adding the mixture of the granule liquid, IBDU powder and urea powder. The obtained granulated material was sieved, and a 2.36-4 mm thing was further dried at 100 degreeC for 1 hour, and it used for the following underwater elution tests.
Water dissolution test:
The produced granular slow-release nitrogen fertilizer 200 mg and sea sand (15 to 20 mesh) 20 g were mixed and packed in a non-woven bag to obtain an elution pack. In a 200 ml styrene container, 200 ml of demineralized water and an elution pack were placed, covered, and placed in a 25 ° C. incubator. After a predetermined period of time, the inside of the container was gently stirred and the nitrogen content of the eluate was measured. The elution rate was calculated from the nitrogen content in the eluate and the amount of charged nitrogen determined in advance. The remaining eluate was discarded, 200 ml of demineralized water was newly added, and it was left in a thermostat at 25 ° C. again. The above operation was repeated until the cumulative elution rate exceeded 80%. Table 2 shows the characteristic values of the granulated product. Moreover, the result of a water dissolution test is shown in FIGS.
[0030]
Comparative Example 1
Fertilizer was granulated and evaluated in the amounts shown in Table 1 in the same manner as in Example 1 except that urea was not used. Table 2 shows the characteristic values of the granulated product. The results of the water dissolution test are shown in FIG.
[0031]
Comparative Example 2
Comparative Example 1 and granular urea were mixed (bulk blended) so that the nitrogen ratio was 90:10 to obtain Comparative Example 2. This was evaluated in the same manner as in Example 1. The result of the water dissolution test of the mixture is shown in FIG.
[0032]
Comparative Example 3
Comparative Example 1 and granular urea were mixed (bulk blended) so that the nitrogen ratio was 70:30, and Comparative Example 3 was obtained. This was evaluated in the same manner as in Example 1. The result of the water dissolution test of the mixture is shown in FIG.
[0033]
[Table 1]

[0034]
[Table 2]

[0035]
As is clear from comparison between Examples 1 and 2 and Comparative Example 1 in FIG. 1, in Examples 1 and 2 in which urea, which is a water-soluble substance, is granulated together with slow-release nitrogen fertilizer IBDU, only IBDU is used. Compared to the granulated Comparative Example 1, it can be seen that the dissolution rate is clearly increased despite the same particle size.
[0036]
Further, as is clear from the comparison between Example 1 and Comparative Example 2 in FIG. 2 and the comparison between Example 2 and Comparative Example 3 in FIG. 3, an example in which urea, which is a water-soluble substance, is granulated together with IBDU. Although 1 and 2 have the same particle diameter and the same urea ratio as Comparative Examples 2 and 3, it can be seen that the elution rate is clearly increased.
As described above, when the easily water-soluble substances were dispersed in the slow-release nitrogen fertilizer, the dissolution rate was clearly higher than when they were simply blended. This means that readily water-soluble substances are eluted immediately after being put into water, the inside of the slow-release nitrogen fertilizer is hollowed out (internal surface area is increased), and the release rate of the slow-release nitrogen fertilizer is increased despite the same particle size. It shows that it has grown. That is, it became possible to control the dissolution rate of slow-acting nitrogen fertilizer with the same particle size, which was difficult in the past.
[0037]
【The invention's effect】
The granular slow-release nitrogen fertilizer of the present invention increases the amount of nitrogen dissolved in the soil at the initial stage of fertilization by quickly eluting the readily water-soluble substance into the soil after fertilization, and remains after the dissolution of the easily water-soluble substance. Compared with conventional granular slow-release nitrogen fertilizers that do not contain readily water-soluble substances of the same particle size, the slow-release nitrogen fertilizer particles have a hollow surface and an increased surface area. The rate of elution of the liquid is improved, and a granular slow-release nitrogen fertilizer with an unprecedented elution pattern can be provided.
[Brief description of the drawings]
FIG. 1 is a diagram showing an elution pattern of granular fertilizers in Examples and Comparative Examples.
FIG. 2 is a diagram showing an elution pattern of granular fertilizer in Examples and Comparative Examples.
FIG. 3 is a diagram showing an elution pattern of granular fertilizer in Examples and Comparative Examples.

Claims

A granular slow-release nitrogenous fertilizer having a continuous phase containing a urea-aldehyde condensate and a dispersed phase containing an easily water-soluble substance, and the weight ratio of the continuous phase to the dispersed phase being 95: 5 to 50:50.

The granular slow-release nitrogenous fertilizer according to claim 1, wherein the readily water-soluble substance is a fast-acting nitrogenous fertilizer.

The granular slow-release nitrogenous fertilizer according to claim 1 or 2, wherein the urea-aldehyde condensate contains 70% by weight or more of a condensate having the same degree of condensation.

The granular slow-release nitrogenous fertilizer according to any one of claims 1 to 3, wherein the urea-aldehyde condensate is a urea-isobutyraldehyde condensate.