Detection Technologies of Soil Fertilizer

Why Test Soil Fertilizer

The detection of soil fertilizer has a great influence on the testing of soil formula fertilization and the use of agricultural fertilizer. In the testing of soil formula fertilizer, the relevant personnel use scientific methods to test the soil fertilizer content, and fertilize the soil according to the test results and soil nutrient content. Scientific detection method has the following advantages:

Detection Technologies of Soil Fertilizer

The detection of soil fertilizer is mainly to detect the chemical elements contained in it, and the most content is nitrogen, phosphorus and potassium.

Determination of nitrogen content

Nitrate is reduced by nitrogen alloy in alkaline medium and then distilled out ammonia; or nitrate is reduced into ammonium salt in acid medium, and concentrated sulfuric acid is used to digest organic nitrogen or amido nitrogen into ammonium salt, distilling nitrogen out of alkaline solution. Nitrogen is absorbed by excess sulfuric acid (or boric acid) solution, and in the presence of methyl red-methylene blue (or bromocresol green) mixed indicator, the nitrogen content was determined by back titration with sodium hydroxide standard solution (or direct titration with sulfuric acid standard solution).

Determination of phosphorus content

The determination of phosphorus content in soil fertilizer generally refers to the determination of total phosphorus, water-soluble phosphorus and available phosphorus, which is generally measured by gravimetric method, plasma emission spectrum and spectrophotometer.

• Gravimetric method

Principle: orthophosphate ion and quinmolybdenone reagent can generate yellow quinoline phosphomolybdate precipitate in acid medium. The weight of quinoline phosphomolybdate can be used to determine the content of phosphorus.

• Plasma emission spectrometry

Principle: the atoms atomized and excited to the high energy state of phosphorus in the ICP light source produce electromagnetic radiation with characteristic wavelength when they transition to the ground state, and the emission intensity is proportional to the concentration of phosphorus atoms.

• Spectrophotometer

Principle: at a certain acidity, phosphate ion reacts with metavanadic acid and molybdic acid to form yellow ternary heteropoly acid. In a certain range of phosphorus concentration, the absorbance is positively proportional to the phosphorus content.

Determination of potassium content

The determination of potassium content in soil fertilizer generally refers to the determination of potassium content and total potassium content, which is generally measured by gravimetric method, flame photometry, plasma emission spectrometry and so on.

• Gravimetric method

Principle: potassium ion was precipitated by sodium tetraphenylborate solution in weakly alkaline medium, and potassium content was determined by potassium tetraphenylborate gravimetric method.

• Flame photometry

Principle: potassium emits characteristic spectrum under the excitation of flame. In a certain concentration range, the emission intensity is proportional to the concentration of potassium in the solution. Under the same conditions as the standard curve, the concentration of potassium can be calculated by measuring the emission intensity of potassium.

• Plasma emission spectrometry

Principle: the atoms atomized and excited to the high energy state of potassium in the ICP light source produce electromagnetic radiation with characteristic wavelength when they transition to the ground state, and the emission intensity is proportional to the concentration of potassium ions.

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