Iron-based nutritive composition

Abstract

The present invention relates to an inorganic solid nutritive composition comprising at least one polyphosphate and at least one source of iron as micronutrient, wherein said composition is water-soluble and comprises an iron content of between 0.1% and 5% by weight of iron relative to the total weight of said solid composition.

Claims

1. An iron-based solid nutrient composition suitable for preparing a solution having substantially non insolubles, comprising a mixture of an iron source, and of a phosphate source, said phosphate source containing at least one polyphosphate, said mixture having an iron content of between 0.1 and 5% by weight relative to the total weight of the composition and a molar ratio P.sub.poly/Fe of between 5 and 50, said mixture being soluble in water and, after dissolution in water, having a percentage of insolubles of less than 0.2% by weight relative to the weight of the composition.

2. An inorganic solid nutrient composition according to claim 1, characterized in that it further comprises at least one additional source of micronutrient selected from the group consisting of sources of B, Mn, Zn, Cu, Mo, Co and the mixtures thereof, and in that the said at least one additional source of micronutrients is contained in an atomic ratio relative to Fe of between 0.1 and 5 for B, between 0.05 and 2.5 for Mn, between 0.01 and 1 for Zn, between 0.005 and 0.25 for Cu and Mo, and between 0.001 and 0.1 for Co.

3. The inorganic solid nutrient composition according to claim 1, wherein the said at least one polyphosphate is selected from the group consisting of sodium and potassium alkaline polyphosphates in powder or granule form.

4. The inorganic solid nutrient composition according to claim 1, wherein the said at least one polyphosphate is selected from the group consisting of pyrophosphates and tripolyphosphates.

5. The inorganic solid nutrient composition according to claim 3 having a molar ratio M/P.sub.total of between 1 and 2, where M represents the total number of moles of sodium and potassium alkaline metal and where P.sub.total represents the total number of moles of phosphorus.

6. The inorganic solid nutrient composition according to claim 1, further comprising phosphorus in orthophosphate form in a molar ratio P.sub.ortho/P.sub.total of between 0 and 0.95, where P.sub.ortho is the number of phosphorus moles in orthophosphate form and where P.sub.total is the number of moles of total phosphorus.

7. The inorganic solid nutrient composition according to claim 1, comprising a dissolution time of less than 15 minutes at 20 C. under magnetic stirring to obtain solution turbidity lower than 50 NTU, and a standard concentration of 10 mmol Fe/kg of solution.

8. The inorganic solid nutrient composition according to claim 1, having a clumping index lower than 100.

9. The inorganic solid nutrient composition according to claim 1, having a storage time of more than 6 months at 25 C.

10. The inorganic solid nutrient composition according to claim 4, wherein said pyrophosphates and tripolyphosphates are selected from the group consisting of: tetrapotassium pyrophosphate (TKPP), potassium tripolyphosphate (KTPP), sodium tripolyphosphate (STPP), sodium acid pyrophosphate (SAPP) and tetrasodium pyrophosphate (TSPP).

Description

(1) Other characteristics, details and advantages of the invention will become apparent from the examples given below that are non-limiting and given with reference to the appended Figures and examples.

(2) FIG. 1 illustrates the results obtained when measuring the biomass of cucumber plants (grams in dry weight) fed with different nutrient solutions.

(3) FIG. 2 gives the iron concentrations (mmol of Fe/kg of dry matter) obtained from measurements of cucumber plants fed with different nutrient solutions.

(4) FIGS. 3 and 4 illustrate the scores recorded after visual estimation of chlorosis in cucumber plants fed with different nutrient solutions.

EXAMPLES

(5) Tests were conducted under laboratory conditions to determine the physicochemical characteristics of the inorganic, solid nutrient composition of the invention. Dissolution, ageing and clumping tests were carried out for which the results are given below.

(6) These different tests were performed after mixing a first component comprising at least one polyphosphate for 30 seconds in a powder mixer (Magimix, type 5200) with a second component comprising at least one iron source. These two components (or raw materials) were used as such without any prior treatment and were added simultaneously to the mixer.

Example 1

Dissolution and Ageing Tests

(7) Six compositions such as reproduced in Table 1 were prepared.

(8) TABLE-US-00001 TABLE 1 Dissolution test Solid composition [Fe] Dissolution Stir Type of poly- MR mmol/kg time time phosphate Iron source (Poly/Fe) solution (min) (min) pH 1 KTPP (a) FeSO.sub.47H.sub.2O (e) 10 10 <10 15 9.4 2 KTPP (b) FeSO.sub.4H.sub.2O (f) 10 50 <15 15 8.7 3 KTPP (a) FeCl.sub.24H.sub.2O (g) 10 50 4 15 ND 4 TKPP (c) FeSO.sub.47H.sub.20 (e) 10 20 5 840 9.8 5 STPP (d) FeSO.sub.47H.sub.2O (e) 14 50 <15 15 ND 6 KTPP (b) FeSO.sub.47H.sub.2O (e) 30 50 <10 15 9.6 (a) 46.4 weight % total P.sub.2O.sub.5, 53.3 weight % K.sub.2O, 1.6 wt. % > 86 wt. % < 0.5 mm (b) 46.6 weight % total P.sub.2O.sub.5, 53.2 wt. % K.sub.2O, 0.6 wt.. % < 2 mm, 34 wt. % < 0.5 mm (c) 42.7 weight % total P2O5, 57.0 weight % of K20 (d) 57.6 weight % total P.sub.2O.sub.5, 42.1 weight % Na.sub.2O (e) 19.2 weight % total iron (f) 28.7 weight % total iron (particle size of 0 to 0.5 mm) (g) 28.0 weight % total iron ND = Non-determined value

(9) Dissolution Test

(10) The solid powder mixtures obtained were immediately placed in a beaker (inner diameter 6 cm) containing dissolution water at 20 C. and stirred with a magnetic rod (length 4 cm) at a rate of 400 revs per minute. Each final solution obtained weighed 250 g and contained a total of 10, 20 or 50 mmol Fe/kg of solution.

(11) After a given stir time, the final degree of dissolution was evaluated by measuring: the turbidity of the solution using a laboratory nephelometer: HACH Ratio/XR; and the concentration of insolubles (residual solid particles).

(12) The content of insolubles for which results are expressed in relation to the initial solid weight, was measured by gravimetric analysis via filtration through a membrane of size 0.45 m (Porafil NC type by Macherey-Nagel), the residue being washed and dried at 105 C.

(13) Quantitative analysis was also performed of the iron contained in this solid residue to determine relative iron loss.

(14) Table 2 gives the characteristics of the six compositions with regard to the criteria of turbidity, percentage of insolubles and iron loss. These criteria were recorded for two different ages of each solubilised composition such as indicated in Table 2.

(15) TABLE-US-00002 TABLE 2 Evaluation 1 of the solution Evaluation 2 of the solution Age of Turbidity Insolubles Iron loss Age of Turbidity Insolubles Iron loss solution (NTU) (wt. %) (relative %) solution (NTU) (wt. %) (relative %) 1 15 min 2 0.06 <1 24 D 2 0.06 <1 2 15 min 40 0.08 <1 21 D 45 0.09 <1 3 10 min 11 0.06 <1 ND ND ND ND 4 10 min <50 0.08 <1 14 H >2000 15 >50 5 15 min 10 0.08 <1 7 D 410 0.7 16 6 15 min 27 0.07 <1 24 D 24 0.08 <1 ND = Non-determined value D = days H = hours

(16) To meet the criteria of the present invention, the placing in aqueous solution of the inorganic solid nutrient composition must allow the obtaining of a nutrient solution in which the different components are fully and quickly dissolved. In the meaning of the present invention, it is considered that all the components are dissolved if: the measured turbidity is lower than 50 NTU; and the weight percentage of insolubles is less than 0.2%.

(17) Also, the iron loss must be less than 5% during the changeover from the solid state to the dissolved state of this metal element.

(18) After a first evaluation performed 10 to 15 minutes after the placing in solution of the said inorganic nutrient composition of the invention, it was ascertained that the different tested compositions (No 1 to 6 in Table 2) all allowed the three criteria to be met irrespective of type of polyphosphate, iron source or iron concentration in the tests conducted.

(19) Similarly it was most advantageously observed that some compositions exhibited an increase in stability, even after dissolution. These were compositions No 1, 2 and 6 which after 20 to 21 days still displayed reduced turbidity and reduced insoluble content.

Example 2

Stability of the Solid Compositions

(20) The product shelf-life and hence stability were determined by subjecting the product to the same dissolution test after different compression times at 25 C. under the conditions of the clumping test described below.

(21) According to the invention the product expires as soon as: the measured turbidity is higher than 50 NTU; and the weight percentage of insolubles is higher than 0.2%.

(22) Two solid compositions of the invention were considered (Table 3) to evaluate whether ageing of the solid form has an influence on its dissolution when placed in solution.

(23) A first composition less than one day old was compared with a second composition 21 days old.

(24) TABLE-US-00003 TABLE 3 Solid composition Dissolution test Type of [Fe] Dissolution polyphos- MR mmol/kg time phate Iron source (Poly/Fe) Age solution (min) pH 1 KTPP (a) FeSO.sub.47H.sub.2O (b) 10 <1 D 50 3 min 8.3 2 KTPP (a) FeSO.sub.47H.sub.2O (b) 10 21 D* 50 5 min ND (a) 46.4 weight % total P.sub.2O.sub.5, 53.3 weight % K.sub.2O, 1.6 wt. % > 1 mm, 86 wt. % < 0.5 mm (b) 19.2 weight % total iron ND = Non-determined value D = days *21-day ageing under compression at a temperature of 25 C.

(25) As can be seen, the two solid forms exhibit an equivalent dissolution time in the order of 3 to 5 minutes for solution turbidity of lower than 50 NTU and weight percentage of insolubles of less than 0.2%, which demonstrates the stability over time of the solid form of the composition of the invention when it is stored at a temperature of 25 C.

Example 3

Clumping Tests (Clumping Index)

(26) Measurement of the clumping index was obtained using a laboratory test developed by the inventors to quantitate the clumping tendency of a solid composition and thereby characterize the composition. This index reflects the mechanical strength of a core sample of the product obtained after a compression time of 21 days at 25 C. in a sealed cell preventing practically all moisture or oxygen exchange with ambient air.

(27) The compression cell comprises two semi-cylinders in stainless steel (obtained by cutting a tube along its longitudinal median) held together around a disc by means of a removable locking plate. The disc also in stainless steel closes the cylinder at its base. The diameter of the disc is 46 m for a height of 10 mm. The cylinder height is 80 mm. The locking plate and two semi-cylinders can be easily removed without jolting the disc. A polypropylene piston sliding freely inside cylinder and surmounted by a weight of 6 kg is used to compress the product from above. The disc-shaped piston has a diameter of 44 mm and height of 30 mm.

(28) The assembly (with the exception of the 6 kg weight) was wrapped in a sachet composed of a multilayer plastic film comprising an aluminium sheet, and was heat welded to prevent any exchange of moisture with ambient air. The sealing of the sachet was verified by gravimetric analysis, the variation in relative weight of the product not to exceed 0.2% over the test time. Homogeneous filling of the cell was ensured by performing this operation progressively whilst rotating the cell. The product was packed using the piston before completion of filling to avoid excessive packing during the actual compression phase. The weight of the composition varied between 70 and 120 g. The top of the piston must project from the cylinder up until the end of the compression phase otherwise there is a risk that the weight will not apply the expected pressure of 0.36 bar. Care must also be taken to ensure that the weight is fully centred relative to the piston.

(29) The assembly was left to stand throughout the entire compression phase. Dynamometric measurement was performed no later than 4 hours after removal of the weight. After removing the locking plate and the two semi-cylinders without jolting the core of product, a dynamometer test bench was used to measure the rupture force of the core. This force was applied vertically to the centre of the disc-shaped piston via a metal tip. The tip was driven forward by the dynamometer test bench at a constant speed of 60 mm/minute. The rupture force in Newtons (N) measured in this manner corresponds by definition to the clumping index. This index is 0 if the product flows at the time of mould release or if the core collapses between mould release and dynamometric measurement.

(30) The dynamometer scale used in the laboratory was limited to 460 N. When this force at the end of the scale was insufficient to cause rupture of the core, the core was subjected to a second dynamometric measurement after withdrawing the piston and replacing the tip with a calibrated blade.

(31) The results obtained for the three inorganic, solid nutrient compositions of the invention are given in Table 4 below. A P.sub.poly/Fe ratio of 10 was set for each of the compositions. A compression time of 21 days at 25 C. was applied.

(32) TABLE-US-00004 TABLE 4 Ageing Rupture Type of before Clumping force with poly- compres- index blade phosphate Iron source sion* (1) (Newton) 1 KTPP (a) FeSO.sub.47H.sub.2O (c) None >460 131 2 KTPP (a) FeSO.sub.47H.sub.2O (c) 24 hours 83 3 KTPP (a) FSO46-7H.sub.2O (b) 24 hours 32 (a) 46.6 weight % total P.sub.2O.sub.5, 53.2 weight % K.sub.2O, 0.6 wt. % > 2 mm, 34 wt. % < 0.5 mm (b) 19.8 weight % total iron (c) 19.2 weight % total iron (1) Rupture force in Newtons with the disc *reaction between the two constituent powders before compression of the mixture resulting in a coating phenomenon.

(33) To meet the criteria of the present invention, the inorganic solid nutrient composition must be able to be stored without an increase in weight. This characteristic is heeded when the clumping index is lower than 100 after compression at 25 C. As shown in Table 4, and for a fixed molar ratio P.sub.poly/Fe of 10, it was found that a clumping index lower than 100 was observed for compositions 2 and 3 i.e. after ageing for 24 hours before compression at 25 C. for 21 days.

Example 4

Hydroponic Culture (Cucumber)

(34) Hydroponic growing tests (substrate-free) in a greenhouse were carried out for 6 weeks to verify the efficacy of the nutrient solution of the invention.

(35) Previously, cucumbers had been seeded in vermiculite to obtain plantlets. These plantlets were transferred 3 weeks after seeding to hydroponic growing conditions i.e. in plastic boxes (503020 cm) fitted with a perforated PVC lid. These boxes were filled with water and nutrient solution and the plantlet roots were placed in the aqueous solution through the perforations of the lid. The lid allowed the nutrient solution to be isolated from the outside medium to prevent penetration of light and/or contaminant which could deteriorate the fertilizing nutrient solution. The aerial portion of the plant was tutored with an inert, flexible material. The boxes were also equipped with nozzles allowing the injection of air into the nutrient solution to provide oxygen to the root system.

(36) The level of water in the boxes was checked twice a week and the amount of nutrient solution adjusted in relation to the electrical conductivity of the nutrient solution. The electrical conductivity of the solution was initially set at 3 mS.Math.cm.sup.1 and was held between 2.5 and 3.5 mS.Math.cm.sup.1 throughout growing time.

(37) The pH of the nutrient solution was measured three times a week and adjusted if necessary through the addition of HNO.sub.3+H.sub.2SO.sub.4 mixture (ratio 12:1) or KOH.

(38) a) Treatments: Tested Iron Sources

(39) Three iron sources (P1 to P3) of the invention containing ferric sulfate were tested at two different pH values of the nutrient solution and compared with a standard commercial organic iron chelate as control (P4). The characteristics of the tested solutions are given in Table 5 below.

(40) TABLE-US-00005 TABLE 5 Fe mmol mol complexing MR Solution Ptotal/l Fe/l pH agent (P.sub.poly/Fe) P1a 1.5 15 5.2-5.6 TKPP (a) 10 P1b 1.5 15 6.4-6.8 TKPP (a) 10 P2a 1.5 15 5.2-5.6 KTPP (b) 10 P2b 1.5 15 6.4-6.8 KTPP (b) 10 P3a 1.5 15 5.2-5.6 KTPP (b) 20 P3b 1.5 15 6.4-6.8 KTPP (b) 20 P4a 1.5 15 5.2-5.6 organic chelate 0 P4b 1.5 15 6.4-6.8 organic chelate 0 (a) 42.7 weight % total P.sub.2O.sub.5, 57.0 weight % K.sub.2O (b) 46.6 weight % total P.sub.2O.sub.5, 53.2 weight % K.sub.2O

(41) The other nutrient elements listed in Table 6 were supplied to the nutrient medium in accordance with recommended standards for cucumber culture.

(42) TABLE-US-00006 TABLE 6 Nutrient Target value NH4 0.1 mmole/l K 8 mmole/l Ca 6.5 mmole/l Mg 3 mmole/l NO3 18 mmole/l SO4 3.5 mmole/l Mn 7 mole/l Zn 7 mole/l B 50 mole/l Cu 1.5 mole/l Mo 1 mole/l

(43) Each treatment was repeated 4 times, each repeat entailing a box containing water and the tested nutrient solution and 2 cucumber plants.

(44) b) Analyses

(45) To evaluate the efficacy of the iron sources P1 to P3 of the invention, the following parameters were measured at the end of growing time (after 6 weeks): production of biomass (dry weight); micronutrient concentrations: tissue analysis.

(46) Statistical analysis (ANOVA, P<0.05) was applied to compare the different treatments.

(47) b.1. Biomass Production

(48) The cucumber plants were harvested after 6 weeks' hydroponic growth in accordance with the above-described conditions. After drying the tissues, the dry weight was determined of the cucumber plants (roots+aerial portion of the plants). FIG. 1 gives the result obtained.

(49) As can be seen, no significant difference was observed between the different treatments applied in terms of biomass at the end of growth.

(50) b.2. Nutrient Concentrations

(51) The nutrient concentrations in mmol/kg dry matter (except for copper in mol/kg dry matter) were determined on dry tissue following techniques conventionally used for the assay of nutrients. The results obtained (n=4) are given in Table 7 below. FIG. 2 only concerns the iron concentration measured from the dry matter.

(52) TABLE-US-00007 TABLE 7 P1a P1b P2a P2b P3a P3b P4a P4b K 1565 1508 1653 1608 1609 1503 1856 1542 Na 18 18 30 17 19 16 26 19 Ca 921 958 911 984 886 958 877 1048 Mg .sup.332.sup.ab .sup.353.sup.ab .sup.323.sup.ab .sup.362.sup.ab .sup.296.sup.a .sup.334.sup.ab .sup.319.sup.ab .sup.377.sup.b P.sub.total 385 371 414 398 375 83 413 396 Fe .sup.8.2bc .sup..sup.5.9.sup.ab .sup..sup.8.2.sup.bc .sup.6.1.sup.abc .sup..sup.9.0.sup.c .sup..sup.5.8.sup.ab .sup..sup.4.9.sup.a .sup..sup.4.5.sup.a N.sub.total 4748 4439 4645 4665 4656 4410 4756 4575 Mn 1.8 .sup.1.9 .sup.1.5 .sup.2.0 .sup.1.6 .sup.2.0 .sup.1.7 .sup.1.7 Zn .sup..sup.2.4.sup.ab .sup..sup.2.3.sup.ab .sup..sup.2.3.sup.ab .sup..sup.2.6.sup.b .sup..sup.2.2.sup.ab .sup..sup.2.3.sup.ab .sup..sup.1.5.sup.a .sup..sup.1.4.sup.a B .sup.4.1 .sup.3.6 .sup.4.1 .sup.3.8 .sup.4.0 .sup.3.9 .sup.4.2 .sup.3.9 Cu 342 349 352 345 371 374 292 330 Mo 106 72 103 80 104 81 104 106

(53) Statistical analysis (ANOVA) evidenced that the plants fed with solutions P1a, P2a and Pa (pH between 5.2 and 5.6) contained more iron than the plants fed with the nutrient solution of reference P4a at this same pH. At higher pH (P1b, P2b, P3b and P4b where the pH was between 6.4 and 6.8) no significant difference was noted for iron, which could be accounted for by lesser complexing on account of the higher baseness of the solution.

(54) b.3 Chlorosis

(55) Throughout the 6 weeks of hydroponic growth, symptoms of iron deficiency were visually evaluated.

(56) Chlorosis, indicative of iron deficiency, was evaluated using scores ranging from 0 (green leaf colour) to 10 (yellow leaf colour). FIG. 3 gives the results obtained when the pH of the nutrient solution was between 5.2 and 5.6 whilst FIG. 4 gives the results obtained when the pH of the nutrient solution was between 6.4 and 6.8.

(57) With these two Figures it can be ascertained that chlorosis having equivalent scores was observed over time for the different treatments applied irrespective of pH.

(58) It was therefore found that the compositions of the invention allow better uptake of macro- and micronutrients by plants, in particular better iron uptake.

Comparative Example

(59) The example of patent CN 1274706 was reproduced on laboratory scale. The solid obtained after the procedure was subjected to the dissolution test in Example 1 of the present invention.

(60) The solution obtained displayed turbidity at 10 mmoles Fe/kg of solution which exceeded 1000 NTU.

(61) The content of insolubles also reached 59% relative to the weight of powder used for the dissolution test. The composition of CN 1274706 is therefore in no way a water-soluble solid composition.

(62) The present invention is evidently not limited to the embodiments described above and numerous modifications can be made thereto without departing from the scope of the appended claims.