Soil nutrient speed meter error

The premise of fertilization is to know how much nutrients the soil can supply and how much nutrients the crop needs to absorb. Calculate the amount of nutrients that need to be applied (mainly nitrogen fertilizer, phosphate fertilizer, and potash fertilizer) based on the difference between the two and the fertilizer utilization rate.

In general, by looking at some textbooks on plant nutrition or books on the use of fertilizers, one can know the total amount of N, P, and K nutrients needed to reach 50 kg of production, and the utilization of fertilizers, and want to understand the nutrients of the soil. The situation requires the analysis of local soil samples.

The commonly used soil nutrient measurement values ​​refer to the conventional methods. This method is an experiment and practice over several decades or even hundreds of years. It has universal practicality, reliability, comparability, and repeatability. It is a classical method for soil fertilizer and plant nutrition. However, the conventional method requires a certain amount of capital investment. Even if it does not count the investment in housing, the investment in reagents, glass instruments and analytical instruments should be at least 30,000 yuan. This condition is more difficult for township-level agricultural technology extension departments and individual owners. The rapid test method came into being.

The rapid test method refers to the operation using some simple methods including simple sample processing, simple sample leaching, simple instruments, and the like. The advantages are low investment, simple operation and no need for too high technical support. The soil (or soil fertility) speedometer currently on the market is actually an improved version of the 72 colorimeter in China.

According to the instructions provided by the manufacturer, I have done a comparison test, that is:

(1) Using speedometers and the analysis methods provided to operate;

(2) Operate using routine analysis methods.

Through the comparison of experiments, it was found that the results obtained by the two analysis methods are: there is a certain correlation between soil available phosphorus, effective potassium, and ammonium nitrogen. Sometimes, rapid measurement instruments do not basically introduce the method for measuring nitrate nitrogen. Therefore, according to the method introduced by the speedometer, only the data of available soil phosphorus can be related to the values ​​of conventional tests. 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 conventional test values. Contact, so its scientificity and accuracy are doubtful.

In addition, the lack of determination of nitrate nitrogen by speedometers is also a major drawback in guiding fertilization (because the routine testing of nitrate nitrogen is cumbersome, the operation is complex, and errors tend to occur, so this method is not easy to quickly measure). As we all know, ammonium nitrogen, nitrate nitrogen and nitrite nitrogen are three kinds of state that crops can easily absorb. After the fertilizer is applied to the soil, the ammonium nitrogen is unstable in the soil and can be rapidly converted to nitrate nitrogen under the action of nitrifying bacteria. The nitrite nitrogen content in the soil is very low, but unstable, it can also Nitrate is rapidly converted to nitrate, so the nitrate nitrogen content in the soil is generally higher than ammonium nitrogen, and the nitrite nitrogen content is the lowest.

Therefore, the best indicator for guiding fertilization is inorganic nitrogen, followed by nitrate nitrogen, and the worst indicator is ammonium nitrogen. The extractors used for the determination of potash by the speedometer were not only sodium sulphate, sodium nitrate, calcium chloride, etc., but ammonium acetate in the conventional analysis was not used (because ammonium ions in ammonium acetate interfered with sodium tetraphenylborate. The turbidimetric method was used to measure the data. Therefore, the data of the two assays can be understood without any correlation.

If fertilization is performed according to the method described in the manual of the speedometer, (1) there is no demonstration of a large number of scientific experiments; (2) the proposed method itself has problems. Therefore, the current rapid measurement technology is inaccurate, and even said that there is suspicion of misleading propaganda. How to simplify the conventional analysis method and develop a test method that can determine the content of soil inorganic nitrogen, available phosphorus and available potassium by simple instruments, and the obtained data are correlated with the data determined by conventional analysis methods, so as to guide the fertilization This is one of the main contents of soil fertilizer workers' work.