Measuring and testing – Sampler – sample handling – etc. – With heating or cooling
Reexamination Certificate
1999-11-02
2001-12-04
Larkin, Daniel S. (Department: 2856)
Measuring and testing
Sampler, sample handling, etc.
With heating or cooling
C073S866000, C422S068100
Reexamination Certificate
active
06324922
ABSTRACT:
BACKGROUND OF INVENTION
1. Field of the Invention
This invention relates to soil nutrient extraction methods and, more particularly, to hot water nutrient extraction systems that are automated and coupled to computer systems for determining fertilizer requirements.
2. Description of Related Art
Increasing demand for soil analysis, prompted by environmental and economic factors, has intensified the need for an inexpensive, fast, convenient, and precise extraction method. Wet chemistry extractions for soil analyses are often labor intensive, complicated, or environmentally hazardous. The extractions are generally tedious, typically involve expensive equipment, require considerable laboratory space, and normally involve the use of numerous chemical reagents. These factors render contemporary soil analysis method prohibitively expensive for all but the most serious agronomic and horticultural pursuits. Simplified soil analysis procedures, if commercially available, are unlikely to extract multiple nutrients in one step and generally require varied reagent use for extractions.
The search for simple, one-step, nutrient extraction method utilizing hot water was probably initiated in the twentieth century by Konig (1906). Anion exchange resin, in combination with water, has been used to measure the total desorption of phosphorus (Amer, et al., 1955). Van der Paaus (1969) proposed that phosphorus (P) extraction efficiency could be improved by using a soil-water ration of 1:50. Korschens, et al. (1984) used the Soxhlet extraction technique, which utilized water, to extract and measure carbon (C) and nitrogen (N) in soils. Suntheim and Matzel (1985) used a continuous water extraction technique to determine phosphorous content in soils. Most recently, a hot water percolation method to extract both macro and micro nutrients was reported for acidic soils of Hungary by Fulkey and Czinkota (1993). Using this method, a mixture consisting of a 30 g soil sample and 10 g of sand was placed on the filter of a coffee percolator and water preheated to 102-105° C. was percolated through the sample under a pressure of 120 to 150 kilopascals (equivalent to about 1.2 to 1.5 bar or 17.4 to 21.75 lbs./in
2
) until about 100 to 500 ml of extract were collected. Results obtained from this latter extraction process compared favorably with plant uptake experiments for acidic soils. Fulkey and Czinkota determined that the time required to obtain 100 ml of extract for percolation through pure soil samples averaged Forty one minutes, while an average of one hundred eighty-eight minutes was required to obtain 500 ml of extract. Because of such unreasonably long percolation times, they determined that it was necessary to dilute the soil samples with sand. They determined that too much sand resulted in such rapid percolation that the amount of nutrients released into the accumulated extract was insufficient for accurate quantitative analysis of the soil sample. Through trial and error, it was determined that a mixture of 25% sand and 75% soil sample, by weight, provided the best combination of reasonable percolation times an average of 2.6 minutes for 100 ml of extract) and adequate release of nutrients into the extract.
What is needed is an improved method for hot water extraction of nutrients from soil samples which is inexpensive, rapidly performed, capable of providing excellent analytical results for a variety of nutrients, and which does not require the mixing of sand with a soil sample. Ideally, such an improved method would make use of readily available equipment which could be used, without modification, to practice the improved method, or which could be readily and inexpensively modified for such practice.
SUMMARY OF THE INVENTION
The invention fills the heretofore expressed need for an improved method of extracting nutrients from soil samples using hot water. The improved method forces pressurized hot water through soil samples to which no filer materials, such as silica sand, had been added. Tests were performed with a Braun model E-250T expresso machine supplied by Braun, Inc., Lynnfield, Mass.). The E-250T generates a pressure of 2.5 bar and a temperature of 93° C.
The method was performed with the following steps. Soils to be tested were air dried at a maximum temperature of 25° C. and passed through a 2.0 mm (number 10 mesh) screen. A 5.0-gram soil sample was placed in the expresso machine's filter basket, which was lined with a 5.50-cm diameter medium filter paper. 100 ml of distilled water was placed in the expresso machine's boiler, and allowed to heat for 2.0 minutes. The heated water was released and passed through the soil sample until the boiler was empty and the filter basket without surface water. This generally occurred in 0.5 to 5 minutes. Extraction aliquots were allowed to cool and the volumes measured (the measured volumes, which ranged from 64 to 91 ml, averaged 79 ml. 10 ml samples from the extraction aliquots were tested for various soil nutrients. Nitrate (NO
3
) content was quantified colormetrically by using a chromatropic acid procedure according to Sims and Jackson (1971). Clarity of the sample for nitrate was determined by adding 0.35 grams of Ca(OH)
2
to a 10 ml sample, the mixture was shaken for five seconds, centrifuged at 2,000 RPM for Forty-Five seconds, and the resultant solution used in nitrate analysis. Sulfate (SO
4
) content was determined using an ion chromatograph. Potassium (K) content was analyzed using an atomic absorption spectrophotometer. The pH value for the sample was determined with a conventional pH meter. Phosphorus (P) content was determined colormetrically using a molybdenum-blue procedure according to Watanabie and Olsen (1965).
For comparison and calibration purposes, the same soils analyzed using the new hot water extraction method were also analyzed for nitrate content, sulfate content, potassium content, phosphorus content, and pH using widely-recognized standard methods. The procedures used are hereinafter identified. Linear regression analysis was employed to predict the relationship between the nutrient values obtained using the new hot water method and the nutrient values obtained via the standard nutrient analysis procedures.
REFERENCES:
patent: 5526705 (1996-06-01), Skotnikov et al.
patent: 5672813 (1997-09-01), Doherty
“Hot Water Percolation (HWP): A new rapid soil extraction method” Gy. Fuleky and I. Czinkota, Plant and Soil 157, 131-135, 1993.
Larkin Daniel S.
Pate & Pierce & Baird
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