Determination of nitrate nitrogen in soil samples
Reagent
Nitrate test strip
Sample processing
100 g of uniformly mixed soil samples were accurately weighed, 100 ml of a 0.01 M CaCl 2 solution was added, shaken for 30 minutes, and filtered.
Sample analysis
Wait 60s, measure the test strip on the reflectometer, and the data will be saved automatically (please refer to the RQflex plus operating instructions and the Reflectoquant ® plus nitrate test package insert). .
data processing
Nitrate nitrogen content (mg/kg) = measured value (mg/kg) x volume of CaCl 2 solution (ml) / mass of soil sample (g)
Determination of ammonium nitrogen in soil samples
Reagent
Ammonium nitrogen test strip
Sample processing
Accurately weigh 150 g of the uniformly mixed soil sample into a beaker, add 600 ml of 0.0125 M CaCl 2 solution (weigh 1.8389 g of calcium chloride dihydrate to 1 L of deionized water), shake for 1 hour, and immediately filter.
Sample analysis
Rinse the sample container with the test solution several times, add 5 ml of the test solution, add 10 drops of NH4-1 reagent and shake well, add 1 tsp of the first blue NH4-2 reagent and shake. Press the reflectometer start button and immerse the analytical test strip in the sample to be tested for 8 or 4 minutes (20 - 30 °C) to ensure that each reaction zone is immersed. The excess liquid is absorbed by the absorbent paper through the long edge zone.
The test strip on the reflectometer is measured and the data is automatically saved (refer to the RQflex plus operating instructions and the Reflectoquant ® plus ammonium nitrogen test package insert).
data processing
Ammonium nitrogen content (mg/kg) = measured value (mg/kg) x volume of CaCl 2 solution (ml) / mass of soil sample (g)
Determination of phosphate in soil samples
Reagent
Phosphate test strip, calcium lactate, 32% hydrochloric acid
Sample processing
Stock solution: Weigh 120g of calcium lactate and add 800ml of deionized water and heat until all is dissolved. After a little cold, add 40 ml of 10 mol/L hydrochloric acid solution, and then cool the solution to room temperature to a volume of 1000 ml.
DL solution: 50 ml of the stock solution was diluted to 1000 ml with deionized water. The pH of the solution must be 3.6.
Accurately weigh 5g of soil sample (particle size less than 2mm) in a beaker, add 250ml DL solution, shake for 90min, and filter.
Sample analysis
Rinse the sample container with the test solution several times and add 5 ml of the test solution. Add 10 drops of PO4-1 reagent and shake well. Press the reflectometer start button and immerse the analytical test strip in the sample to be tested for 2 seconds (15 - 30 °C) to ensure that each reaction zone is immersed. Remove excess sample from the test strip.
Wait 90s, measure the test strip on the reflectometer, and the data will be saved automatically (please refer to the RQflex plus operating instructions and the Reflectoquant ® plus phosphate test package insert).
data processing
Phosphate content (mg/100g) = measured value x volume of extractant (ml) / (soil sample mass gx 10)
Determination of potassium in soil samples
Reagent
Potassium test strip, calcium lactate, 32% hydrochloric acid solution
Sample processing
Stock solution: Weigh 120g of calcium lactate and add 800ml of deionized water and heat until all is dissolved. After a little cold, add 40 ml of 10 mol/L hydrochloric acid solution, and then cool the solution to room temperature to a volume of 1000 ml.
DL solution: 50 ml of the stock solution was diluted to 1000 ml with deionized water. The pH of the solution must be 3.6.
Accurately weigh 10 g of soil sample in a 200 ml Erlenmeyer flask, add 60 ml of DL solution, shake for 60 min, and filter.
Sample analysis
Add 5 ml of soil sample solution to the beaker, add 10 drops of K-1 reagent, add 6 drops of K-2 reagent and mix, add 1 teaspoon of first blue K-3 reagent, dissolve and shake.
After 30 s, the soil samples were mixed and placed in two small measuring instruments along with the blanks and measured on a reflectometer. The measured values ​​are automatically saved (refer to the RQflex plus operating instructions and the Reflectoquant ® plus potassium test package instructions).
data processing
Potassium content (mg/100g) = measured value (mg / L) x volume of extractant (ml) x 100 / (sample mass gx1000)
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