Soil testing sampling knowledge

The minimum nutrient law, the crop yield is controlled by the least nutrient in the soil, the output varies with the amount of this nutrient, if this nutrient is not added, even if other nutrients are added, the crop yield does not increase. For example, the lack of nitrogen in soil, no increase in nitrogen fertilizer, and continuous application of phosphorus and potassium fertilizer, crop yield can not be increased. Corresponding to the minimum nutrient law, the maximum nutrient law is that excessive nutrients also limit the increase in yield. For example, in the case of nitrogen deficiency in soil, if nitrogen fertilizers are continuously increased, the yield will continue to increase. However, if it is increased to a certain extent and then nitrogen fertilizer is applied, the yield cannot be increased but rather decreased. Therefore, the rational and economical fertilization of crops requires the mastery of basic soil conditions such as nitrogen, phosphorus, potassium, and organic matter. How to sample it?
1, sampling time: crops such as grain and oil canola before sowing, fruit trees after fruit harvest period.
2. Depth: For shallow crops (rice, etc.) with root distribution, pick 0-20 cm; for crops with deep root distribution (fruit trees), pick 0-40 cm.
3, sampling points: an area of ​​less than 10 acres, take 5-10 points; 10-40 acres, take 10-15 points; more than 40 acres, take 15 points or more.
4. Distribution of sampling points: The landform is tidy, the fertility is uniform, and the diagonal method is used; the area is large and the topography is irregular using the serpentine method.
5. Sampling method: At the sampling point, use a shovel to shovel the side of the earth pit into a vertical shape. Scoop up about two centimeters of thick soil from the top to the bottom, and take a piece of soil that is about 5 centimeters wide. Samples.
6, sample weight and processing: diagonal sampling. Crushed, mixed, and rounded all samples, and then removed two copies of the diagonal line. If there are more samples, repeat it again until 0.5-1 kg is left in the sample.
7, send samples: the sample into the bag, written in a pencil, tie the bag mouth to send samples.
8. Note: Do not take samples of plots, roadsides, ditch edges, fertilizer heaps, and front crop fertilization sites. All tools used for sampling should be as clean as possible to obtain more accurate results.

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