(1) Soil sample collection
The depth of soil sample collection is 20cm, and the representative area is generally not more than 50mu. It is mainly serpentine or zigzag. When sampling, first scrape the surface soil of 2-3cm, and collect the soil piece with depth 20cm, width 10cm and rear 1-2cm. The sampler should be inserted perpendicular to the ground to a depth of 20cm. The collected soil samples should be crushed, and the mixed materials such as gravel, animal and plant residues should be removed, fully mixed, and reduced to 0.5 kg by the quartering method. In the bag, both inside and outside of the bag are required to have a label, and the sample number, the name of the sampled plot, the date of sampling, the sampler, and the like are written in a pencil.
(2) Soil sample test
1. Determination of soil alkaline nitrogen: at a certain temperature, the hydrolyzable nitrogen in the soil is hydrolyzed to ammonium nitrogen, together with the original ammonium nitrogen in the soil, and escapes in the state of nitrogen, using a filter paper impregnated with acid The block was absorbed and then measured by Nessler's reagent colorimetric method.
2. Determination of soil available phosphorus: After the available phosphorus in the soil is leached, it is usually determined by molybdenum blue colorimetric method. Under certain acidity and suitable concentration of other reagents, phosphate and ammonium molybdate form phosphomolybdic acid, which is reduced. The blue complex is a phosphorus molybdenum blue, and the blue color is proportional to the concentration of phosphorus. 0.5M NaHCO3 can inhibit the activity of Ca2+, so that the more active Ca-P is leached, and the relatively active Fe-P and Al-P can be leached by hydrolysis.
3. Under the condition of pH 5-10, potassium ions react with sodium tetraphenylborate to form a stable precipitate of potassium tetraphenylborate, which makes the solution turbid. In a certain concentration range, the turbidity is proportional to the concentration of potassium.
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