There are many soil nutrient testing methods, which can be divided into routine analysis, rapid measurement, ion pooling, and soil nutrient system research.
In our country, the alkaline hydrolysis of nitrogen in traditional soils is generally determined by NaOH hydrolysis and diffusion by Kronweek. The nitrate nitrogen is extracted by potassium sulfate at a ratio of 5:1, shaken for 15 min, and the filtrate is treated with a silver nitrate electrode. Method determination; Olsen method for soil available phosphorus (0.5 mol/L NaCO3), Bray-1 method (0.03 mol/L NH4FC0.025 mol/L HCl) and Mehlich-3 method (0.2 mol/LCH3COOH + 0.25 mol/L NH4NO3 + 0.015 mol/L NH4F + 0.013 mol/L HNO3 + 0.001 mol/L EDTA) was used as extractant and molybdenum antimony was measured by colorimetric method. Determination of effective potassium was usually performed with 1 mol/L neutral ammonium acetate, flame spectrophotometer. Determination of effective Mn in soil: DTPA extractant (0.005mol/L DTPA+ 0.01mol/L CaCl2+0.1mol/L TEA, pH=7.30); soil available Zn, Cu, pH<7.3, extraction with 0.1mol/L HCl At the time of pH > 7.3, the ZnPA, Cu, K, and Mn simultaneously extracted by the DTPA extractor capable of extracting effective Mn were all determined by an atomic absorption spectrophotometer. This method is highly accurate, but the analysis is slow and cannot be applied in time to guide practice.
First, the rapid measurement method, soil nutrient fast test is a widely used analysis method at home and abroad for many years, is also a means of agriculture and science and education for mass scientific farming, soil nutrient measurement instrument is a relative Routine analysis results in faster speed, lower cost, and simpler test equipment. Test accuracy can meet soil nutrient testing techniques and equipment required for soil and fertilization.
The so-called rapid soil nutrient measurement method simplifies the routine analysis method for effective nutrients, such as reducing the volume of the extract solution, shortening the extraction time, simplifying the extraction and determination steps, and using visual colorimetry to make the operation quick and easy. The results have a certain degree of accuracy and are easily grasped by the masses. Because of the relatively simple and quick extraction method used for speed measurement, certain nutrients can not be completely extracted, and the measured nutrient quantity is generally lower than conventional analysis. The greatest workload of soil analysis is pre-treatment. To increase the speed of measurement, simultaneous rapid extraction of multiple nutrients must be achieved. It can be said that the joint extraction technology is the basis of the rapid measurement method (Duan Tiecheng, 2002). In recent years, Mehlich-3 combined extractant, calcium chloride extractant and ASI combined extractant have been widely used in domestic research. This method is fast, can be a large number of tests, and guide the practice in a timely manner; but the measured amount is lower than the conventional method.
Second, the ion pooling method mainly absorbs and collects ions to be measured from the soil by a surface that adsorbs ions to be measured. Mainly can be divided into ion exchange resin and iron oxide test paper method, which ion exchange resin can be divided into ion exchange resin beads, ion exchange resin bags and ion exchange resin membrane and other methods. This method can simulate the nutrient absorbed by the root system and accurately determine the soil's effective nutrients, but it also has the disadvantages of slow operation speed and ununiform standards.
Third, the soil nutrient status system research method, which is gradually developed over the years on the basis of international soil testing and recommended fertilization research. Hunter of Agro Services International Inc of Florida, USA, based on previous soil testing work, absorbed the research results of Waugh, Cate, and Nelson from North Carolina State University in the United States. A set of laboratory analysis and pot experiment methods for the evaluation of soil nutrient status was proposed in the year and was officially published in 1984. In 1988, Portch of the Canadian Potassium Phosphorus Institute slightly modified this method and later began to use it in cooperation projects with China.
Fourth, soil nutrient system research method is a set of technology integration, including five parts:
(1) Collection and treatment of soil samples;
(2) laboratory analysis;
(3) Adsorption tests of soil nutrients;
(4) Greenhouse or net room pot experiment;
(5) Field trials. This method comprehensively considers comprehensive consideration of the status, balance, and balance of large, medium, and trace elements in the soil; the use of joint extractants improves work efficiency; we can basically understand the nutrient status of the soil through indoor analysis and pot experiment, and fertilizer application. Some reactions after entering the soil have enabled us to avoid blindness in the design of experiments and to save manpower and material resources. In field research, we can achieve the highest yield targets and formulate a rational balance fertilization plan to achieve a balanced fertilization in the true sense. However, this method has many links and is more complex; the soil basic fertility analysis and adsorption test require higher equipment and means, and the equipment required for the pot-planting test is also relatively special, and it is difficult to popularize it in the grass-roots agricultural sector.
In the current soil nutrient testing methods, each method has its advantages and disadvantages. We must select a reasonable measurement method according to the nature of each soil, the accuracy of the test requirements, and the economic conditions, so as to better The result of the measurement guides fertilization and achieves true balanced soil fertigation.
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