GB 7855-1987 Determination of slowly available potassium in forest soils GB7855-1987 standard download decompression password: www.bzxz.net

National Standard of the People's Republic of China
Determination of slow release potassium in forest soil
Determination of slow release potassium in forest soil This standard is applicable to the determination of slow release potassium in forest soil. This standard adopts 1 mol/L nitric acid boiling extraction-flame photometry. 1 Key points of the method
UdC 634.0.114
GB 7855-87
Boil the slow release potassium in the soil with 1mol/L nitric acid solution. The extraction time is short, the amount of reagent consumed is small, and the coefficient of variation of multiple measurements is small. It is often used as an indicator of the potential supply of soil potassium. The amount of potassium extracted by the 1mol/L nitric acid boiling method minus the quick-release potassium is the slow release potassium content.
2 Reagents
2.1 Extraction agent (1m0l/L nitric acid solution): 62.5ml concentrated nitric acid (analytical grade) is added to a 1L volumetric flask pre-filled with 500ml water, shake well, and make up to volume.
2.2 0.1mol/L nitric acid solution: dilute 1mol/L nitric acid solution 10 times. 2.3 Potassium standard solution: take 100ppm potassium (K) (same as GB7854-87 "Determination of total potassium in forest soil" 1.2.5) standard solution 1, 2.5, 5, 10, 15, 25ml respectively into a 50ml volumetric flask, add 10ml of 1mol/L nitric acid solution, and then dilute with water to obtain 2, 5, 10, 20, 30, 50ppm potassium (K) standard series solutions. 3 Main instruments
Flame photometer; tall conical flask (150ml), container flask (50ml) 4 Determination steps
4.1 Weigh 5.0g (accurate to 0.01g) of air-dried soil sample that has passed through a 2mm sieve into a 150ml conical flask, add 50ml of 1mol/L nitric acid solution, place a small funnel at the mouth of the flask, place the conical flask on a thermostatic electric stove, and boil slowly for 10min. Do not allow the test solution to overflow. Filter it while hot into a 250ml volumetric flask, rinse the soil four times with 0.1mol/L nitric acid, 15ml each time, and then dilute to the scale with water. This solution can be directly used to measure potassium with a flame photometer, record the galvanometer reading, and then find the potassium concentration (ppm) of the measuring solution from the working curve. 4.2 Drawing of the working curve: Same as GB7854-871.4.3. 5 Result calculation
.1mol/L nitric acid soluble potassium (K, ppm) = c×v×is
m1×K2
1mol/L nitric acid soluble potassium (K, mg/kg) = 1mol/L nitric acid soluble potassium (K, ppm). (2) Slow-acting potassium (K, ppm): = 1mol/L nitric acid soluble potassium (K, ppm) - fast-acting potassium (K, ppm) (3)
slow-acting potassium (K, mg/kg) = 1mol/L nitric acid soluble potassium (K, mg/kg) - fast-acting potassium. (K, mg/kg) (4)
In the formula: c——the ppm number of potassium in the reading solution obtained from the working curve: reading solution volume, 250ml, www.bzxz.net
approved by the National Bureau of Standards on June 4, 1987
1988 -01 ~01 implementation
Allowable deviation
-Multiple times of sampling, ts:
GB 7855 - 87
Volume of liquid to be tested (m1)
Volume of liquid to be tested (ml)
Moisture conversion factor from air-dried soil sample to dried soil sample, mass of air-dried soil sample, g.
According to the provisions of Table 1 and Table 2 of GB7849-87 "Determination of hydrolyzable nitrogen in forest soil". Note: The temperature should be uniform during heating, and should not fluctuate. The boiling time should be strictly controlled; the boiling time of 10 minutes is counted from the beginning of boiling. A large amount of carbon dioxide bubbles will occur when carbonate soil is boiled, which should not be mistaken for boiling. Additional remarks:
This standard was proposed by the Ministry of Forestry of the People's Republic of China and is under the jurisdiction of the Forestry Research Institute of the Chinese Academy of Forestry. This standard was drafted by the Department of Soil and Plant Nutrition of Zhejiang Agricultural University. 163
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