COMPOSITION WITH GLASS-BORNE PLANT NUTRIENTS

Abstract: Compositions with glass-borne plant nutrient, the glass being on a phosphate base, and a method of manufacturing such compositions. The new compositions are characterised in that the alumina content (Al2O3) is lower than in known compositions or they may be manufactured entirely without Al2O3. Instead, titanium dioxide (TiO2) in the form of ilmenite mineral, rutile or technically pure TiO2 is used as additive to regulate the solubility. Methods have been devised to produced such compositions by melting at 900-1300<o>C in a furnace with walls of highvalency refractory material. As raw product for the manganese in the compositions, manganese dioxide can be used in the form of pyrolusite which is converted to bivalent manganese during melting.

Description: Composition ωith glass-borne plant nutrients. The present invention relates to a product ωith specially com¬ bined glass particles containing microπutrieπts, and to a method of manufacturing these. The need for trace elements in agriculture has increased in re- cent years, due to the increasing yield demands both in the pro¬ duction of "animals and of crops. The need for trace elements for animals is relatively simply to fulfil by mixing various soluble salts into mineral fodder. However, the problems of supplying trace elements in crop cultivation are considerable and varied, primarily due to variations in the soil as a chemical environ¬ ment. It is primarlily alkaline and acidic soils ωhich cause re¬ actions of various kinds. In Scandinavia the most frequently occurring problem is in conjunction ωith stabilizing manganese. Manganese is also a problem internationally, and specific crops like fruit, berries and maize in alkaline soil also entail pro¬ blems ωith zinc and iron. Chelates- o various types are current¬ ly used to solve this plant nutrient problem. The chelates are generally used in the form of additives ωhεn watering, or as leaf sprays. Salts of various types are normally also added to ferti— lizers and leaf sprays. The drawbacks ωith chelates are that they aTB expensive and must be applied frequently, often several times a year. The achieve long-term effect glass has been used containing micro- nutrients ωhich are gradually leached out of the glass. The base for the glass carriers used in the microπutrient mixtures noω commercially available is silicates. However, due to their high alkali content, these types of glass are less suitable as carriers for manganese, for instance, ωhich is easily deposited in basic environments in the form of manganese hydroxide and is thus biolo- gically difficult to utilize. Silicate glass also gives rise to O '.Pl A r WIP0 silicon gel ωhich is difficult to dissolve and the solubility is therefore reduced ωith time. Glass based on phosphate has there¬ fore been assumed to be a better carrier since, ωith this type of glass, the pH value can be regulated upon release to the acid side or the manganese ions can be kept in solution by suquestering even if the environment is alkaline. The release rate should also be more uniform due to the absence of colloidal layer on the surface of the fertilizer particles. Another advantage ωith phosphate glass would be that the carrier material itself, which consists primarily of phosphates, can also be used as plant nutrient. Proposals have already been put forward for the use of phosphate glass. Such glass is made of phosphorus pentoxide ^O-. and the solubility of the glass is generally regulated by the inclusion of calcium oxide CaO. These types of phosphate glass were de- veloped to be used in combination with calcium cyanamide and give a fertilizer which acts slowly. Phosphate glass especially desig¬ ned to fulfil the soil's iron requirement is also known. The main components in a typical composition for this purpose are P Om* and FeO, with the addition of a few per cent K 0. Through the present invention new types of glass carriers have been developed adapted to icronutrients, primarily manganese, and surprisingly good results have been achieved. An essential part of our invention is that ωe have developed glass carriers ωith loω Al content or no Al at all. A draωback ωith previously knoωn gla,ss carriers on a phosphate base has been the high Al con¬ tent ωhich may entail risks of Al poisoning in the root system. This is a threat to forestry and -agriculture. In the following the manufacture of glass containing manganese will be described in more detail. OMPI Manufacture of manganese glass The aim was to manufacture a glassy -product which, by slowly, con¬ tinuously dissolving, gives off manganese over a relatively long period of time, perhaps about 10 years, and provides soil poor in 2+ manganese ωith a necessary addition of Mn ions. The glass should have a particle size suitable for existing spreaders (1-2 mm) and the quantity to be spread is also determined by the manner in ωhich the machines operate, giving about 200 kg glass frits per hectare. If the manganese can be released uniformly over a 10-year.period, ca. 10 Mn content in the glass ωill give the desired quantity of Mn. • An important requirement is also that the manganese released remains in soluble form and accessible for absorption by the crops. The carrier was phosphate-based glass which can be adjusted to slightly acid or almost neutral properties and by sequestering can keep the Mn ions in solution even in slightly alkaline environment, as well as having a more uniform release rate since no colloidal layer is formed on the surface of the particles. The dissolving rate of the glass is regulated by the addition of stabilizing oxides. The glass should contain 55-65% P to make it easy to melt, stable against crystalization and to avoid unnecessary evaporation of P ^ O during melting. It was found that 10% Mn, corresponding to 12,9% MnO is the manganese concentration ωhich provides the desired Mn addi¬ tion. A considerable quantity of alkali in the form of Na_0 or K_0 is desirable to stabilize the glass and regulation of the dissolving rate can be achieved by the addition of CaO and/or A1„0„. The choice between K_0 and Na„0 is dependent on economic factors since sodium compounds are less expensive but potassium compounds contri¬ bute to the macroπutrieπt supplement to the soil. Both alternatives were investigated, as well as combinations thereof. CaO was selecte'd as dissolving rate stabilizer, primarily from the cost point of view, but since CaO alone did not give the desired dissolving rate, A1,_0„ was also used. O PI v The following raw products were used : Name Formula Oxides Manganese carbonate MnC0 3 MnO . Manganese acetate Mn(CH 3 C00) 2 .4H 2 0 MnO Pyrolusite Mπ0„ MnO Potassium dihydrogen phosphate KH_P0. κ 2 o, P 2 O 5 Sodium hexameta phosphate (NaPD 3 ) 5 N 2 0, P 2 0 5 Aluminium phosphate A1P0 A1 2°3 > P 2°5 Tricalcium phosphate Ca 3 0 4 CaO, P 2 0 5 Ammonium dihydrogen phosphate NH 4 H 2 P0 4 P 0 *2 5 Calcium carbonate aC0 3 CaO Sodium carbonate a 2 C0 3 Na £ 0 The procedure for melting the glass was as follows: Batches for 100 or 200 g glass were melted in 250 ml quartz crucib¬ les (ROTOSIL, Hersus) in an electric furnace. The melting temperature varied between 900 C and 1300 C, depending primarlily on the Al-0 content. 2-3 batches were inserted at"intervals of 5-10 mins. 30 minutes after the last batch was inserted, the melt was stirred with an A1„0_ rod. After one hour the melt was poured out onto a steel plate. The quantity of manganese dissolved ωas determined as folloωs: Precisely 1 g crushed glass fraction 1-2 mm ωas weighed into a 500 ml polythene bottle and 250 ml 0.01 M phosphate buffer pH 6.6 was added. Stirring was accomplished by intermittent rotation of the bottle 5 miπ/h with the aid of a program. 10 ml of the leach solution ωas taken out. filtered, washed in di- ι stilled ωater and topped up to exactly 50 ml. The quantity of manga¬ nese in this solution ωas determined using a flame spectrophotometer. Examples of glass compositions and leaching results are given in f Table 1 beloω. The glass compositions have been calculated theo¬ retically ωithout taking into account ^O c losses ' during the melting The actual ~ r_,~- may be considered εomeωhat loωer. Some of the glass compositions contained 20 or 30% MnO, respectively, in order to in- vestigate the possibility of using glas ωith higher Mn contents, as well as to assess the effect of the MnO content on the solubility of the glass. Some general observations concerning the feasibility of manufac¬ turing the glass compositions are as follows: ° 1. The P^O-. content should be at least 55%. Crystallization is likely to accur below this limit. 2. The A1 9 0„ content should be limited to 10%. Crystallization occurs at higher contents, or there is a risk of undissolved remnants. 3. CaO contents above 10% cause crystallization. Samples were removed from the leaching experiments after 1, 4, 7 and 14 days. It ωas found that 1 day ωas too short a time for most of the glass compositions and the most soluble compositions gave cloudy solutions. After 14 days no analysis could be performed. The most complete series ωas Mn contents dissolved after 7 days and a statistical evaluation has therefore been carried out on the basis of these results to calculate the effect of the components on the solubility. The effect of the A1„0„ content is shown in Diagram 1. This diagram shows that there is a practical limit of about 5% A1 9 0„, ωhich gives maximum stabilization effect and any increase gives no further im- provemεnt. As a microπutrient, manganese should be in bivalent form. When pro¬ ducing the experimental glass compositions, therefore, manganese OMPI WiP0 was added in bivalent form, either as carbonate or acetate. How¬ ever, in normal production probably only pyrolusite (Mn0 9 ) is feasible from an economic point of view. It proved possible to reduce MnO to bivalent manganese. Three dif— ferent glass compositions were melted, having the same procεntual composition: M 30 Mn added in- the form of Mn acetate M 31 Mn added in the form of MnO (pyrolusite) M 32 Mn added in the form of Mn0„ 4- 25% carbon (coke) After melting polyvalent manganese was determined in. the glass with the Following results: ~ - 30 could hot be determined M 31 0.006% M 320.03% That M 32 had a somewhat higher content, despite the carbon additive, might be due to different melting times since this glass foamed more. The essential factor is that, irrespective of the valency stage of the raw material, Mn is reduced to bivalency in the phosphate glass. Some of the glass compositions were examined to determine the pH value of the solution. Variation was found to be between pH 6.4 and 7.3, i.„e. neutral. Orientated corrosion tests with chamotte material at 1000 C and a 5 day- corrosion period showed extreme corrosion and the melting ωas therefore performed in higher valency smelt—cast refractory -material such as Fondal (quartz block from Dider Werkεn) or ZAC . (Electro Rε- fractaires). Table 1 1 ' Des. P 0 MnO -_ - N 2 0 ! AI 2 O 3 ' CaO !Mn released as % of total 25 7 days 14 day M 20 55.0 13.0 20.2 0 •4.0 7.8 ' 2.2 3-3 M 22 55.0 13-0 16.2 0 8.0 7.8 0.8 1.2 M 25 55.0 13-0 0 16.2 8.0 7.8 0.6 0.9 M 27 55.0 13-0 24.0 0 8.0 0 0.8 1.2 M 33 60.0 12.9 11.1 0 8.0 8.0 0.7 1.0 M 34 65.0 12.9 6.1 0 8.0 8.0 { 0.4 0.5 K 36 i 65.0 12.9 4.1 0 10.0 : 8.0, 0.4 0.6 M 40 60.0 20.0 11.1 0 8.0 1.0, 0.7 1.6 M 43 60.0 .20.0 9-0 0 ■ ' 10.0 i.oj 0.5 1.0 M 46 65.0 12.9 6.1 0 : 12.0 ϋ.-oj 0.2 0.3 M i|8 65.0 30.0 5.0 0 0 - ! . 7.4 11.8 The compositions were tested in a leaching column and compared ωith MnSO.. This substance obviously had the greatest solubility. The leaching here ωas ca. 3000 Mg over a 5-day period. The corresponding leaching rate from the most easily dissolved glasses, M 20 and M 48, ωas ca. 12 Mg per 7-day period. For the glasses most difficult to dissolve, M 34 - M 46, thε leaching varied between 5 and 1 Mg over a corresponding period. The glasses were also tested in a receptacle experient using soil poor in Mn. The soil was thoroughly fertilized and the various glass composi¬ tions were t ' hen mixed in. The receptacles were then sown with grain cultivated in soil poor in Mn. The experiments showed that the glas¬ ses had provided an adequate supply of Mn ωithout the content of leached Mn bεing noticεable. Results of thε cultivation experiment are given in Table 2. ' The production of phosphate glass having a low content of Al o 0- Experiments have shown that titanium dioxide, Ti0 9 , can be used as solubility-regulating component instead of A1„0,. Various types of Ti0 9 material can be used, such as pure Ti0 (its conventional use being as colour pigment) , rutile-mineral and ilme. nitε. The latter mineral consists substantially of TiO , FeO and Fe 2 0 3 . The following are descriptions of thε phosphate glass produced using ilmεnite, by way of example. The il eπite usεd was of Norwεgian origin. A typical analysis for Norωεgian ilmeπite is the folloωing: Ti0 2 44 , .5 % FeO 34. .0 Fe 2°3 12, .5 MgO 5. .0 Si0„ 2. , 7 0 , .6 A1 2°3 99.3 % remainder: CaO, MnO, Cr 0 , P 2 ° c » In the experiments described bεloω ilmεnitε concεntrate in finely milled form ωas used. Thε results can be seen in Table 3 shoωing a phosphate glass MTi in comparison ωith the glassεs M48, M20 and M27 and a glass containing ZnO. The glasses ωere produced in thε same manner.- As can be seen from thε table, in MTi 8% A1 9 0 in thε comparison glas M27 has been replaced by 8% ilmeπite. From the leaching experiments it is clear * that ilmenite has a much greater effect on the ωater so¬ lubility, than A1 0„. A desired solubility can be set by adjusting the quantity added. Therε ωεre no problems during melting. This new type of phosphate glass containing TiO has many advantages when it comεs to producing compositions ωith glass-bornε plant nu¬ trients. Glass can be produced ωhich has a loω A1 0„ content or no Al Q at all. The titanium dioxide has been found to be a micro- nutrient able to give increased harvests and is in any case not damaging. The use of il enite concentrate enablεs compositions to bε manufactured at loω cost. Thε iron in thε ilmenite may also be useful. OMPI - ** WIPO Diagram 1 % dissolved Mn 7—day period % A1 2 0 3 OMPI TABLE 2 EFFECT OF VARIOUS Mn-FERTILIZERS (PEAT SOIL) Harvest of oats and rape and Mn content thersin Treatment Control 3.6 27 200 85 M48 69 3.6 28 591 289 M48 7 4.2 28 Gla98 264 128 M20 30 4.6 ' 28 327 152 M20 3 5.1 29 211 101 3d 5.1 26 484 228 Mn-aulphatθ added to soil 3 4.3 24 230 88 0.3 5.1 27 204 89 TABLE 3

Claims: CLAIMS 1. Composition ωith glass-borne plant nutrient, the glass being on a phosphate base, c h a r a c t e r i s e d in that the composition contains phosphate glass ωith an alumina content (A1„0„) varying betωeen low and no alumina at all. Composition according to claim 1, c h a r a c t e r i s e d iinn tthhaatt ttiittaanniiuumm ddiiooxxiiide (TiO„) is used as additive to re- gulate the solubility. Composition according to claim 2, c h a r a c t e r i s e d iLnn tthhaatt tthhee ccoonntteenntt of titanium dioxide (TiO,-) varies bet- ωeen 0.1 and 10.0^. Composition according to claims 1—3, c h a r a c t e r ¬ i s e d in that Ti0_ is added in the form of ilmenite mineral. •5. Composition according to claims 1—3, c h a r a c t e r i s e d in that Ti0„ is added in the form of rutile mineral. 6. Composition according to claims 1—3, c h a r a ct e r ¬ i s e d in that technically pure TiO is used. 7. Composition according to claims 1-6, c h a r a c t e r ¬ i s e d in that the composition contains manganese. 8. Composition according to claim 7, c h a r a c e, r i s e d in that the manganese is bivalent. JTJREΛ OMPI WIPO 9. Method of manufacturing a composition according to one or more of claims 1-8 by melting at temperatures between 900 and 1300 C, c h a r a c t e r i s e d in that the components are supplied to a furnace hauing walls of high- valency smelt-cast refractory material of quartz block type. 10. Method according to claim 9. c h a r ac t e r i s e d in that manganese is supplied as manganese dioxide (Mn0„) 'in the form of pyrolusite and that during melting the manganese dioxide is converted to bivalent manganese in the phosphate glass .formed. OMPI

Inventors: LAKATOS TIBOR, SIMMINSKOELD BO, WIBERGER INGVAR, LAKATOS, TIBOR, SIMMINSKOELD, BO, WIBERGER, INGVAR
Applicants: CHEMICAL DYNAMICS SWEDEN AB
Application year: 1983
Main classification: C05G3
IPC codes: C05B17