The soil nutrient measurement values we usually refer to are the test values obtained by conventional methods. This method has been tested and practiced for decades or even centuries, and has universal practicality, reliability, comparability, and repeatability. It is a classic method in the fields of soil fertilizers and plant nutrition. However, conventional methods require a certain amount of capital investment, even without including the investment in housing, the investment in reagents, glassware, and analytical instruments should be at least 30000 yuan or more. This condition is more difficult for agricultural technology promotion departments and individual planting owners at the township level. The rapid testing method has thus emerged.

Rapid testing method refers to the operation carried out using some simple methods, including simple sample processing, simple sample extraction, simple instruments, and so on. The advantages are small investment, simple operation, and not requiring too much capital. The soil (or soil fertilizer) rapid testing instrument currently on the market is actually an improved version of the previous 72 type colorimeter in China.

According to the user manual provided by the manufacturer, the author has conducted comparative tests, namely: (1) using a speed tester and the provided analysis method for operation; (2) Perform operations using conventional analysis methods.
Through experimental comparison, it was found that there is a certain correlation between the results obtained by the two analysis methods: soil available phosphorus has a certain correlation, available potassium has no correlation, ammonium nitrogen sometimes has no correlation, and rapid measuring instruments basically do not introduce the determination methods of nitrate nitrogen. Therefore, according to the method introduced by the rapid testing instrument, only the data of soil available phosphorus can be compared with the values of conventional testing, while nitrogen and potassium, which are closely related to fertilization, can only be fertilized according to the amount described in the instrument manual and cannot be compared with the values of conventional testing. Therefore, its scientificity and accuracy are questionable.

In addition, the failure of the rapid testing instrument to measure nitrate nitrogen is also a major drawback in guiding fertilization (because the conventional testing process for nitrate nitrogen is cumbersome, complex to operate, and prone to errors, so this method is not easy to quickly measure). *Ammonium nitrogen, nitrate nitrogen, and nitrite nitrogen are all three easily absorbed states by crops. After fertilizer is applied to the soil, ammonium nitrogen is unstable in the soil and can be quickly converted into nitrate nitrogen under the action of nitrifying bacteria. Although the content of nitrite nitrogen in the soil is low, it is unstable and can also be quickly converted into nitrate nitrogen. Therefore, in general, the nitrate nitrogen content in the soil is higher than that of ammonium nitrogen, and the nitrite nitrogen content is the lowest.

So the * indicator used to guide fertilization is inorganic nitrogen, followed by nitrate nitrogen, and the worst indicator is ammonium nitrogen. The leaching agents used for measuring effective potassium with a rapid analyzer are mainly sodium sulfate, sodium nitrate, calcium chloride, etc., and none of them use the recommended ammonium acetate in conventional analysis (because the ammonium ions in ammonium acetate interfere with the determination of sodium tetraphenylborate turbidity method). Therefore, it can be understood that there is no correlation between the data obtained from the two measurements.

If fertilization is carried out according to the method described in the manual of the speed tester, due to (1) the lack of extensive scientific experimental verification; (2) The recommended method itself has problems. So the current speed testing technology is inaccurate, and there is even suspicion of misleading advertising. How to simplify conventional analysis methods and develop a testing method that can determine the content of soil inorganic nitrogen, available phosphorus, and available potassium using simple instruments, and the obtained data is correlated with the data determined by conventional analysis methods, thus guiding fertilization. This is one of the main contents of the work of soil fertilizer workers