Soil Fertility Testing and Grade Analysis Report: How to Fertilize Rationally?
Vigorously promoting rational fertilization can prevent excessive fertilizer application and also benefits the sustainable use of farmland. Rational fertilization means that farmers adjust the amount and method of fertilizer application according to the growth characteristics of the crop variety, in combination with soil conditions and properties, the types and characteristics of fertilizers, and the growth response of crops after the fertilizer is applied to the soil.
Soil is the foundation of crop growth. During cultivation, applying too much fertilizer not only wastes fertilizer resources and pollutes the environment over the long term - for example, nitrogen fertilizer contaminating groundwater and excessively high nitrate concentrations in plants - but also easily causes the soil to become "sick" and degraded, making it difficult to provide elements for crop uptake, which in turn affects yield and quality.
Soil Fertility Analysis Report: An Important Basis for Rational Fertilization
In today's world, where science and data are increasingly valued, the "soil fertility analysis report" is an important reference for farmers when adjusting fertilizer application rates and improving fertilizer use efficiency as part of rational fertilization. At present, agricultural research institutes and improvement stations provide free soil fertility analysis services, and they write articles and hold training sessions to teach farmers how to take samples. Farmers can also pay to commission institutions with laboratory accreditation to conduct tests.
To obtain a soil fertility analysis report with reference value, farmers must collect representative soil in the correct way, so that the tested data will not differ greatly from the actual conditions.
Huang Jui-chang reminds farmers that when sampling, tools such as round-point shovels, transplanting trowels or soil augers must be cleaned thoroughly. Remember that the soil should not be too wet, and soil samples should be sent to the testing unit as far as possible 3 to 4 weeks before applying base fertilizer. As for sampling frequency, short-term crops such as leafy vegetables should be sampled and submitted for testing at least once a year and do not need to be sampled every cropping season; for long-term crops such as fruit trees, sampling and submission can be done once every 1 to 2 years.
To hold the soil sample, you can use sample bags made by the improvement station or a clean plastic bag, and write your name, address, contact phone number, crop type, section and parcel number, etc. on the sample bag. After sending it to the agricultural research institute or improvement station, you can receive the soil fertility analysis report in about 2 to 3 weeks.
Thoughtful Annotations from Agricultural Authorities: Farmers Can Understand at a Glance
The soil fertility analysis report contains 7 categories of items: soil electrical conductivity (EC), soil pH, soil organic matter, and soil available phosphorus, potassium, calcium and magnesium. Huang Jui-chang adds that some farmland is saline land, and the agricultural improvement station will additionally test sodium, so that sodium ions in the soil do not affect soil aggregate structure and harm crop uptake of potassium and calcium ions and root growth. When farmers receive the soil fertility analysis report, in addition to listing the test values for the 7 categories of items, values that are too high are marked in red, while blue indicates lower values that can be strengthened. The report also includes fertilizer recommendations for the planted crop from researchers at the agricultural improvement station, so farmers no longer feel confused when interpreting the report.
The coded soil samples are sent to the soil air-drying room to avoid being affected by moisture during analysis.
Using a soil fertility analysis report for cherry tomatoes that he had on hand as an example, Huang Jui-chang noted that the phosphorus, potassium and magnesium values on the report were all too high. He suggested that farmers reduce phosphorus and potassium fertilizer to avoid antagonism that affects the uptake of iron, zinc, copper, calcium, magnesium and boron; excessive magnesium fertilizer should also be avoided to prevent hindering calcium and potassium uptake.
There is antagonism among different nutrients. If certain elements are difficult to absorb, the deficient elements can also be supplemented through foliar fertilizer. Huang Jui-chang says that for general short-term crops, referring to the soil fertility analysis report to improve fertilizer use efficiency is enough; if farmers want to understand the uptake status and nutritional disorders of long-term crops such as fruit trees, they can further conduct plant tissue (leaf) nutrient diagnostic analysis. The sampling position and timing for different crops can be found in the website information of agricultural research institutes and improvement stations, or by calling to ask.
As for the insufficient soil organic matter in the soil where cherry tomatoes were planted, as shown in the report, this will reduce soil aggregate structure and nutrient availability. Huang Jui-chang says that if it is sandy soil, good drainage is less of a problem, and it is recommended to apply low-nutrient organic compost with high plant crude fiber content, such as bark compost, bagasse compost, cow manure compost, rice straw or rice hull compost, at about 600 to 800 kg per fen. However, the disadvantage of sandy soil is that it does not retain fertilizer easily, so fertilizer must be applied in small amounts many times, and the recommended fertilizer amount should be increased by 10% to 20%.
Because each piece of farmland has different characteristics, researchers at agricultural research institutes and improvement stations must act like detectives, considering local soil characteristics, whether farmers use open-field or protected cultivation, and based on crop type and commonly used fertilizers, unraveling the situation step by step and evaluating each value before making the most suitable fertilization recommendation. Huang Jui-chang also used another cherry tomato farmer's soil fertility analysis report as an example. The report showed a pH of less than 5.5, electrical conductivity of 2.3 dS/m, phosphorus of more than 500 mg/kg, and potassium of more than 1,500 mg/kg. Not only was the soil acidic, but electrical conductivity, phosphorus and potassium were also much higher than normal values.
"It may be that the farmer over-applied phosphorus and potassium fertilizer to make the fruit sweeter, creating 'pseudo-acidity'; true acidity would show lower calcium and magnesium." Huang Jui-chang says this situation is very common in protected cultivation because, without rainwater leaching, fertilizer easily accumulates excessively. In that case, magnesia lime cannot be used for improvement, lest electrical conductivity become even higher. Instead, farmers should be advised to leach salts to wash away acid radical ions, and the pH will naturally rise again.
The Testing Process Is Tedious; Simple Testers Can Be Used When Urgent
So that farmers have a basis before fertilizing, agricultural research institutes and improvement stations now almost all try to send soil fertility analysis reports to farmers within about 2 weeks. Huang Jui-chang says that usually during autumn or spring cropping, the number of soil samples submitted for testing is relatively large. Because the jurisdiction of the Tainan District Agricultural Improvement Station covers agricultural counties and cities such as Yunlin, Chiayi and Tainan, in September to October this year, for example, it received more than 1,000 samples per month on average, and the time farmers wait for reports may be extended to 3 weeks.
Farmers can use simple testers for pH and electrical conductivity to obtain data immediately and fine-tune the direction of fertilization. (Image provided by Huang Jui-chang)
Some farmers report that waiting for reports takes too long, but in fact the process after sampling and submission is quite complicated. When agricultural research institutes and improvement stations receive soil samples, they must first register each sample and insert a number tag for easy classification and quick retrieval later. After coding, the soil is spread on a sample tray to remove weeds and stones, then placed in a large constant-temperature ventilated cabinet. After air-drying for 7 to 10 days, it is taken out and sieved, ground into fine powder, and placed into sample paper boxes. Next, an extractant must be added to the soil sample to exchange the anions and cations in the soil out and dissolve them in the extractant.
Only after completing the above sample pretreatment process does it enter the machine analysis stage. Next to laboratory testing instruments, the snack "Kuai Kuai" is often seen placed there, symbolizing the testers' hope that the testing process will go without mistakes and the machines will operate smoothly.
The data for the 7 categories of fertility analysis items are obtained through instrument analysis. Professional staff check whether the data are normal, then compile them into a soil fertility analysis report. The report is handed to experts responsible for different crops to write fertilization recommendations and send to farmers, and only then is the task complete. Taking the Tainan District Agricultural Improvement Station as an example, it has different experts responsible for rice, cherry tomatoes, muskmelon, miscellaneous grains, flowers and organic crop cultivation. They divide the writing of fertilization recommendations according to their respective specialties and attach contact phone numbers. If farmers still have questions after reading the report, they can call to ask, or join the agricultural improvement station's dedicated social media group. For example, the Tainan District Agricultural Improvement Station has a LINE@ life circle, where farmers can immediately upload photos or write messages to ask about crop nutrition and pest and disease management methods.
Of course, after farmers receive the soil fertility analysis report, it does not mean everything will be foolproof from then on. Huang Jui-chang says the report cannot predict the climate and crop growth conditions 2 to 3 months later. Farmers should still continuously accumulate experience, fine-tune fertilization in line with crop growth conditions and climate change, and can usually attend agricultural training sessions to increase relevant knowledge.
If farmers still feel that the testing process is time-consuming or urgently need reference values, Huang Jui-chang suggests that farmers can buy simple testers for pH and electrical conductivity at chemical raw material stores. One unit costs about 1 to 3 thousand yuan, and data can be obtained immediately after testing as a reference for fine-tuning fertilization. "By mastering pH and electrical conductivity, you can basically understand soil fertility conditions. Nowadays, many farmers involved in protected cultivation and emphasizing precision agriculture have purchased them."
The soil fertility analysis report can be said to be the painstaking work of laboratory staff at agricultural research institutes and improvement stations. A reliable report depends on correct soil sampling methods, sample pretreatment, operation and maintenance of analytical instruments, and interpretation of figures. Through soil health checks, farmers can be helped to discover and adjust soil problems early and move ever closer to the goal of rational fertilization.
However, how exactly should rational fertilization be carried out in practice? Huang Jui-chang, associate researcher in the Crop Environment Section of the Tainan District Agricultural Improvement Station (hereinafter referred to as the Tainan District Agricultural Improvement Station) under the Council of Agriculture, Executive Yuan, and known as a "soil nutritionist," explains that rational fertilization includes 3 steps: first, sample the soil for fertility analysis; second, fine-tune fertilization in line with crop growth conditions and climate change; and finally, because fertilizer is not 100% absorbed and utilized by crops after application, efforts should be made to improve fertilizer use efficiency.