Soil testing laboratory commonly used centrifuges have low speed, high speed centrifuges, and all kinds of centrifuges with refrigeration function. Low speed centrifuge (including large capacity) is the most widely used. Centrifuge is an important tool in soil detection.
In order to solve the problems of heavy chemical fertilizer, light organic fertilizer, blind fertilization and excessive fertilization, soil testing and formula fertilization technology should be widely used in order to improve the utilization rate of fertilizer, reduce the waste of fertilizer resources, reduce agricultural non-point source pollution, protect the ecological environment and ensure the sustainable development of agriculture.
1 The necessity of centrifuges
The composition of soil solution plays an important role in predicting the biological availability of nutrients to plants, especially when solution concentration is expressed as a single ion activity. To determine the activity of ion species in soil solution, it is necessary to prepare an extract that can accurately reflect the real soil solution. To prepare the soil solution, a centrifuge is used.
2 Centrifuge usage steps
Before each test, check whether the centrifuge speed control knob is in zero, whether the outer sleeve is intact, rubber pad, sealing apron is dislocated, the sealing apron of the door to ensure good sealing, after a period of time will be coated with vacuum sealing grease. If the sealing ring is found to be aging, cracking and losing elasticity, it should be replaced immediately.
The collection method of soil samples is to obtain undisturbed samples with the ring knife matching the centrifuge, and each soil sample takes 4 repeated samples. Soil samples were brought back to the laboratory, saturated with water for 48h, and centrifuged by high-speed refrigerated centrifuge [3]. Before centrifugation, the centrifugal soil sample should be transferred into the appropriate centrifugal tube, and the amount should be 1~2cm away from the mouth of the core tube, so as not to be thrown out during centrifugation.
(1) Balance each centrifugal tube well.
(2) Connect the power supply and turn on the switch.
(3) After setting centrifugal speed, time and other parameters, place the balanced sample tube.
(4) after centrifugation, the centrifuge itself to stop turning to start, can hit the boot cover, take out the centrifuged soil sample.
(5) Turn off the switch, cut off the power supply, and clean the centrifuge inside and outside.
3 Precautions before use
3.1 Selection of centrifugal tube
When loading the prepared soil samples, the specific operation instructions of various centrifuges should be carried out according to the nature and volume of the samples to be centrifuged. When using the centrifugal tube without a lid, the samples should not be loaded too much to prevent being thrown out during centrifugation. It is strictly prohibited to use centrifugal tubes that are significantly deformed, damaged or aged.
3.2 balancing
The balance of the centrifuge must be balanced using a balance to accurately balance the centrifuge tube and its contents. Note that when balancing, refer to the centrifuge instruction manual. Generally, there is a specified range of weight difference between each centrifuge tube in the instruction manual, and pay attention not to exceed this specified range.
3.3 Centrifugal tube placement method
When placed in a centrifuge tube, must pay attention to is absolutely can't load the singular pipe, when not loaded with centrifugal tube in turn, is only part of the loading, the centrifugal tube must be symmetrically placed in turn to each other, so that the force evenly distributed around the turn, so as to avoid uneven during high speed centrifugal force, the centrifugal GuanFei out of danger.
4 Precautions in use
In the process of centrifuge work, the operator shall not leave at will, should observe the centrifuge on the instrument is normal work, once there is abnormal sound should immediately stop check, and timely troubleshooting.
4.1 Matters needing attention when turning heads
The rotating head is the key part to be protected in the centrifuge. The rotating head has a certain weight, so be careful when moving it to avoid collision and avoid scars. Each turnhead has its maximum allowable speed and cumulative time limit. When using the turnhead, it should be used within the specified speed according to the provisions in its manual, and overspeed is strictly prohibited. Each turning head should have a use file, record the cumulative use time, if exceeds the maximum use limit of the turning head, it must be used in accordance with the regulation. After each use, carefully check the turning head, dry it in time and clean it well. Turn the head for a long time when not used, to be coated with a layer of glazed wax protection.
5 Matters needing attention after centrifuge use
After the centrifuge is used, special attention should be paid to not contaminate the inner cavity of the centrifuge, and pay attention not to fall into dust and oil stains. After wiping clean, it is recommended to open the top cover and keep the centrifugal chamber dry. Note that when cleaning the centrifuge, the rotor, centrifugal chamber and so on can generally be cleaned with water or neutral detergent. Acid and alkaline solutions or corrosive solvents are prohibited.
6 Other precautions
6.1 The centrifuge must be placed on a flat and solid ground or on the test table, and it is not allowed to be tilted.
6.2 Centrifuges should be kept at a certain distance from other electrical equipment, and good grounding measures should be taken, and regular inspection should be carried out to ensure safety.
6.3 After the centrifuge is started, if there is abnormal noise or vibration, it should be shut down immediately.
