METHODS FOR EARTH ANALYSIS

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is a PCT International Application claiming the benefit of United States Provisional Patent Application No. 62 / 792542, filed on January 15, 2019.BACKGROUND

[0002] Soil analysis of agricultural fields allows a grower to know whether there are sufficient amounts of nutrients in the soil for planting. If one or more nutrients is deficient, then the nutrient can be added to soil.

[0003] Typically, soil samples are obtained via a bag and tag system in which soil samples are obtained from multiple locations in a field, placed in a bag, tagged with the information of where the soil sample was taken in the field, and then shipped to a lab for testing. This takes time, and the grower needs to wait for the test results before being able to take action.

[0004] Current soil tests are usually laborious in that soil samples are first dried to a target moisture and then ground to provide a dry soil of uniform particle size for testing. This adds processing time and costs to the testing procedure.

[0005] There are many standardized soil tests available today, such as measurement of pH with a pH meter and measurement of soil nutrients by atomic spectroscopy. These tests, however, were designed for laboratory testing, and they are not suitable for an on the go soil sampling system.

[0006] It would be desirable to test soil samples on the go with soil tests that can provide results while in the field.BRIEF SUMMARY

[0007] The invention provides in a first aspect a method of measuring pH of a soil slurry as defined in claim 1; the method comprises: a) obtaining a soil extract; b) adding Bromocresol green and Nitrazine yellow in a weight ratio of Bromocresol green to Nitrazine yellow of 0.1: 1 to 100: 1 to the soil extract to form a mixture; and c) measuring absorbance of the mixture.

[0008] The invention provides in a second aspect a method of measuring buffer pH of a soil slurry as defined in claim 7; the method comprises: a) obtaining a soil extract; b) adding a buffer to the soil extract; c) adding methyl red and bromothymol blue in a molar ratio of 2.5:1 to 50:1 to the buffer and soil extract to form a mixture; and d) measuring absorbance of the mixture.

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[0018] The present invention is expressly not limited to use with soil sampling at any particular location but can be used at any location.DETAILED DESCRIPTION

[0019] The features and benefits of the invention are illustrated and described herein by reference to exemplary ("example") embodiments. This description of exemplary embodiments is intended to be read in connection with the accompanying drawings, which are to be considered part of the entire written description. Accordingly, the disclosure expressly should not be limited to such exemplary embodiments illustrating some possible non-limiting combination of features that may exist alone or in other combinations of features.

[0020] As used throughout, any ranges disclosed herein are used as shorthand for describing each and every value that is within the range. Any value within the range can be selected as the terminus of the range. In the event of a conflict in a definition in the present disclosure and that of a cited reference, the present disclosure controls.

[0021] The compositions and methods described below can be used with on the go soil sampling systems, such as those described in U.S. Patent Publication No. US2018 / 0124992, or in U.S. Application Nos. 62 / 696,271, filed 10 July 2018; 62 / 729,623, filed 11 September 2018; and 62 / 745,606, filed 15 October 2018. Also, the tests and methods can be used in a laboratory. When used in on the go systems, it is desirable to obtain results in a short period of time (shorter than traditional laboratory testing) so that multiple samples can be tested while traversing the field. This allows a grower to adjust application rates of nutrients in real time.

[0022] In one embodiment, the methods below can be used in a colorimetric analysis system. This allows for a minimization of testing equipment.pH Test

[0023] In the method of the first aspect, as defined in claim 1, pH is tested using a combination of Bromocresol green (2,6-Dibromo-4-[7-(3,5-dibromo-4-hydroxy-2-methyl-phenyl)-9,9-dioxo-8-oxa-9λ6-thiabicyclo[4.3.0]nona-1,3,5-trien-7-yl]-3-methyl-phenol, 3,3',5,5'-Tetrabromo-m-cresolsulfonphthalein Bromocresol green, CAS 76-60-8) with Nitrazine yellow (2-(2,4-Dinitrophenylazo)-1-hydroxynaphthalene-3,6-disulfonic acid disodium salt, 2-(2,4-Dinitrophenylazo)naphthol-3,6-disulfonic acid disodium salt, Nitrazol Yellow, CAS 5423-07-4). In one embodiment, pH is tested using a composition that includes a soil extract and Bromocresol green and Nitrazine yellow in a weight ratio of Bromocresol green to Nitrazine yellow of 0.1:1 to 100: 1. In other embodiments, pH is tested whereby the weight ratio of Bromocresol green to Nitrazine yellow is 0.2:1 to 20: 1. In one embodiment, pH is tested using an indicator composition having 0.01 weight% to 0.02 weight% Bromocresol green, 0.0125 weight% to 0.025 weight% Nitrazine yellow, and a liquid. A non-limiting example of the liquid is water, but other liquids can be used.

[0024] In one embodiment, the indicator composition is added in an amount of 40 to 120 µL per mL of soil extract. In this amount, absorbance at 615 nm is increased or maximized. In one embodiment, the absorbance machine is an Agilent Cary 100 UV-Vis spectrophotometer. In one embodiment, color will develop after mixing in about 10 seconds after mixing.

[0025] The soil extract can be prepared as follows. Soil taken directly from the ground can be used without first drying and grinding. A soil sample can be mixed in a 1:2 weight to weight ratio with a liquid, such as water, to form a slurry. In other embodiments, a weight ratio of soil to liquid is 1:1 to 1:5. The slurry is then mixed with a flocculating agent. Examples of flocculating agent include, but are not limited to, calcium chloride, polyacrylamide, cationic polyacrylamide, anionic polyacrylamide, polydiallyldimethyl ammonium chloride (PDADMAC), epichlorohydin / dimethylamine copolymer (ECH / DMA), chitosan, and polyaluminum chlorides. In one embodiment, the flocculating agent is calcium chloride. In another embodiment, the flocculating agent is a combination of polyacrylamide and calcium chloride. In another embodiment, the flocculating agent is polyacrylamide. The amount of flocculating agent varies on the type of flocculating agent chosen. The flocculating agent amount can be chosen to remove organic materials and / or reduce or eliminate cloudiness. In one embodiment, a 0.017M CaCl 2 ·2H 2 O solution is used. Alternatively, the anhydride or other hydrates of calcium chloride can be used. In one embodiment, a molar concentration for calcium chloride is 0.005M to 0.1M. The soil slurry is mixed with the flocculating agent in a volume ratio of 4:1 soil slurry:flocculating agent. In other embodiments, a volume ratio of slurry to flocculating agent is 1:1 to 10:1. In another embodiment, the calcium chloride solution can be replaced with a 0.025 weight% polyacrylamide solution. In one embodiment, the polyacrylamide can have a weight average molecular weight of 5,000,000 to 6,000,000 (CAS 9003-05-8). Other flocculating agents can be used in amounts that provide the same amount of flocculation as the above calcium chloride or polyacrylamide solutions. The soil slurry and flocculating agent are centrifuged to form the soil extract.

[0026] To convert absorbance readings to pH, an empirical correlation can be obtained as follows.

[0027] Soil samples are prepared as for typical laboratory testing by drying, crushing, and filtering to less than 2 mm particle size. Multiple samples are prepared to provide a sufficient number to generate a calibration curve. Soil is mixed in a 1:1 weight ratio with water for 5 minutes, and the pH is measured by a pH probe (an Orion ™< 8103BNUWP Ross Ultra ™< pH electrode). Each of these soil samples are then processed with the above method of mixing with the flocculating agent, centrifuging, adding the indicator composition, and then measuring absorbance. The results are logged into a correlation chart and a correlation plot is obtained.

[0028] A calibration curve can be obtained and used with the correlation chart. Flocculating agent solution before adding indicator composition is measured for absorbance to establish a blank reading. The indicator composition (as described above) is then added to this sample and remeasured for absorbance. The difference in the absorbance readings is used for a calibration curve. This will provide the pH of the flocculating agent, such as the calcium chloride. This calibration can be done as needed, such as once per day. The calibration curve is used to adjust the correlation chart.Buffer pH Test

[0029] In the method of the second aspect, as defined in claim 7, buffer pH is tested using a combination of methyl red (2-{[4-(Dimethylamino)phenyl]diazenyl}benzoic acid) with bromothymol blue (4,4'-(1,1-Dioxido-3H-2,1-benzoxathiole-3,3-diyl)bis(2-bromo-6-isopropyl-3-methylphenol), CAS 76-59-5). In one embodiment, buffer pH is measured using a composition that includes methyl red and bromothymol blue in a molar ratio of 20:1 to 30:1. In other embodiments, buffer pH is tested whereby the molar ratio of methyl red and bromothymol blue is 25:1. The mixed indicator solution can be made by taking 1% methyl red indicator in water and mixing it 1:1 with 0.04% bromothymol blue in a 90 / 10 water / ethanol mixture to make a final concentration of 0.5% methyl red, 0.02% bromothymol blue in a 95 / 5 water / ethanol solution by weight.

[0030] In some embodiments, the buffer is added to the soil extract before adding the methyl red and bromothymol blue. The soil extract can be prepared as described above for the soil slurry. The soil slurry can be combined with a buffer solution in a volume ratio of 4:1 slurry to buffer. In one embodiment, the volume ratio is 1:1 to 10:1. In one embodiment, the buffer solution is Sikora buffer. Sikora buffer is available from GFS Chemicals of Powell, Ohio, and it is about 85.6% water, 13.7% potassium chloride, 0.278% triethanol amine and balance minors. Optionally, a flocculating agent can be added (as described above, for example using polyacrylamide as described above) and centrifuged to form a filtrate.

[0031] In one embodiment, the indicator composition is added in an amount of 60 to 120 µL per mL of filtrate. In this amount, absorbance at 617 nm is increased or maximized. In one embodiment, the absorbance machine is an Agilent Cary 100 UV-Vis spectrophotometer. In one embodiment, color will develop after mixing in about 10 seconds after mixing.

[0032] To convert absorbance readings to buffer pH, an empirical correlation can be obtained as follows.

[0033] Soil samples are prepared as for typical laboratory testing by drying, crushing, and filtering to less than 2 mm particle size. Multiple samples are prepared to provide a sufficient number to generate a calibration curve. Soil is mixed in a 1:1 weight ratio with water for 5 minutes, and the SMP (Shoemaker, McLean, and Pratt) buffer pH is measured by a pH probe (an Orion ™< 8103BNUWP Ross Ultra ™< pH electrode) using the standard lab procedure for SMP buffer pH. Each of these soil samples are then processed with the above method of mixing with the buffer (e.g., Sikora buffer), centrifuging, adding the indicator composition, and then measuring absorbance. The results are logged into a correlation chart and a correlation plot is obtained.

[0034] A calibration curve can be obtained and used with the correlation chart. Soil slurry before adding indicator composition is measured for absorbance to establish a blank reading. The indicator composition (as described above) is then added to this sample and remeasured for absorbance. The difference in the absorbance readings is used for a calibration curve. This will provide the pH of the buffer (e.g., Sikora buffer). This calibration can be done as needed, such as once per day. The calibration curve is used to adjust the correlation chart.

[0035] The following further analyses and compositions are described but not claimed.Potassium Analysis

[0036] Potassium can be tested using a combination of reagents including sodium tetraphenylborate, sodium tetraborate, and a polyol (such as glycerol). In one embodiment, a first solution contains 60 mM to 100 mM (or 2 weight % to 3.5 weight%) sodium tetraphenylborate in the solution, or about 87.7mM (or 3 weight %) sodium tetraphenyl borate. A second solution contains sodium tetraborate at 0.85 mM to 1 mM (or about 0.938 mM) and 0.25 M to 0.4 M ( or about 0.327 M) glycerol. In one embodiment, the composition contains about 87.7 mM (about 3 weight%) sodium tetraphenylborate, about 0.938 mM sodium tetraborate decahydrate, and 0.327 M (about 2.4 or 2.38 weight%) glycerol. Optionally, the first solution and second solution can be prepared as a single solution.

[0037] The soil extract can be prepared as follows. Soil taken directly from the ground can be used without first drying and grinding. A soil sample can be mixed in a 1:2 weight to weight ratio with a liquid, such as water, to form a slurry. In other embodiments, a weight ratio of soil to liquid is 1:1 to 1:5. The slurry can then be extracted with an extractant, such as nitric acid. In one embodiment, nitric acid concentration is 0.005 to 0.2 M. In one embodiment, a volume ratio of extractant to soil slurry is 4:1. In other embodiments, the volume ratio is 1:1 to 10:1. A benefit to using either of these extractants is that a shorter extraction time can be obtained, such as 20 seconds or less or 10 seconds or less. This allows for faster processing while testing on the go.

[0038] Optionally, a flocculating agent can be added (as described above, for example using polyacrylamide as described above, such as at 0.01 weight %) and centrifuged to form a filtrate.

[0039] Optionally, a base, such as lithium hydroxide, can be added before or after centrifuging to remove interfering materials. In other embodiments, sodium hydroxide can be used. In one embodiment, a concentration of lithium or sodium hydroxide is 0.05 to 0.2M.

[0040] The extract is then centrifuged. A sufficient amount of base is added to remove the interfering materials.

[0041] In one embodiment, the base is added after extraction. In one embodiment, the extract before the base is added and potassium concentration is diluted 25 to 35 fold by the addition of the base, the first solution, the second solution, and optional water.

[0042] The extract is then mixed with the sodium tetraphenylborate, sodium tetraborate decahydrate, and glycerol reagent. In one embodiment, the first solution is mixed with the extract with a weight ratio of extract to tetraphenyl borate of 2:1 to 1:1, optionally 1.5:1. In one embodiment, the second solution is mixed with the extract in a weight ratio of sodium tetraborate to extract of 3:1 to 6:1, optionally 5.4:1. In this amount, absorbance at 420 nm is increased or maximized. In one embodiment, color will develop after mixing in about 10 seconds after mixing. In one embodiment, the absorbance machine is an Agilent Cary 100 UV-Vis spectrophotometer.

[0043] To convert absorbance readings to potassium levels, an empirical correlation can be obtained as follows.

[0044] Soil samples are prepared as for typical laboratory testing by drying, crushing, and filtering to less than 2 mm particle size. Multiple samples are prepared to provide a sufficient number to generate a calibration curve. The traditional test for potassium in soil is conducted using the ammonium acetate extraction using 1 g of soil and 10 parts of a 1M ammonium acetate solution at pH 7, mixing, filtering with filter paper, and then measuring by ICP-OES. The test can be referenced in Recommended Chemical Soil Test Procedures for the North Central Region, North Central Regional Research Publication No. 221, Missouri Agricultural Experiment Station SB 1001, August 2015 (http: / / extension.missouri.edu / explorepdf / specialb / sb1001.pdf). Alternatively, the Mehlich-3 extractant can be used instead of 1M ammonium acetate at pH 7. The samples are also measured using the above potassium test and the results are correlated for a correlation curve.

[0045] A calibration curve can be obtained and used with the correlation chart. Soil slurry before adding indicator composition is measured for absorbance to establish a blank reading. The indicator composition (as described above) is then added to this sample and remeasured for absorbance. The difference in the absorbance readings is used for a calibration curve. This calibration can be done as needed, such as once per day. The calibration curve is used to adjust the correlation chart.

[0046] A calibration curve can be obtained and used with the correlation chart. Soil slurry before adding indicator composition is measured for absorbance to establish a blank reading. The indicator composition (as described above) is then added to this sample and remeasured for absorbance. The difference in the absorbance readings is used for a calibration curve. This calibration can be done as needed, such as once per day. The calibration curve is used to adjust the correlation chart.Cartridge

[0047] In one embodiment, a multichamber cartridge can be provided in which each chamber contains one of the above compositions in a combination that tests for at least two of the above listed tests (e.g., two or more of the pH test, buffer pH test, potassium test, phosphorous test, calcium test, and / or magnesium tests). In one embodiment, the cartridge has a chamber for the pH test composition, a chamber for the buffer pH test composition, a chamber for the potassium test composition, a chamber for the phosphorous test composition, a chamber for the calcium test composition, and a chamber for the magnesium test composition. In one embodiment, any of the cartridges can contain an additional chamber that does not contain any of the compositions for the above tests.

Claims

1. A method of measuring pH of a soil slurry, the method comprising: a. obtaining a soil extract; b. adding Bromocresol green and Nitrazine yellow in a weight ratio of Bromocresol green to Nitrazine yellow of 0.1:1 to 100:1 to the soil extract to form a mixture; and c. measuring absorbance of the mixture.

2. The method of claim 1, wherein a weight ratio of Bromocresol green to Nitrazine yellow is 0.1:1 to 20:1.

3. The method of claim 1 or claim 2, wherein the Bromocresol green and Nitrazine yellow are provided as a composition that comprises 0.01 weight % to 0.02 weight % Bromocresol green and 0.0125 weight % to 0.025 weight % Nitrazine yellow, and a liquid.

4. The method according to any one of claims 1 to 3, wherein the soil extract is prepared by: a. obtaining a soil sample; b. adding a liquid to the soil sample to volumize the soil; c. mixing the liquid and soil to form a soil slurry; d. filtering the soil slurry; e. adding a flocculating agent to the soil slurry; and f. centrifuging the soil slurry to form the soil extract.

5. The method of claim 4, wherein the liquid is water, and a weight ratio of soil to water is 1:1 to 1:5.

6. The method of any one of claims 3 to 5, wherein the Bromocresol green and Nitrazine yellow is added in the form of an indicator composition comprising Bromocresol green and Nitrazine yellow and the composition is added in an amount of 40 to 120 µL per mL of soil extract.

7. A method of measuring buffer pH of a soil slurry, the method comprising: a. obtaining a soil extract; b. adding a buffer to the soil extract, c. adding methyl red and bromothymol blue in a molar ratio of 2.5:1 to 50:1 to the buffer and soil extract to form a mixture; and d. measuring absorbance of the mixture.

8. The method of claim 7, wherein the molar ratio of methyl red to bromothymol blue is 20:1 to 30:1.

9. The method of claim 8, wherein the molar ratio of methyl red to bromothymol blue is 25:1.