1. distribution: sampling should be based on the distribution of soil types and crop varieties and different soil fertility. The sampling points are zigzag or serpentine, and should be as uniform and random as possible.

2. Determine the sampling position and depth: the sampling position and depth should be determined according to the thickness of the plough layer, and the sampling depth is generally 0-20cm. ?

3. Sampling season and time:? The collection place and time of the backbone agrochemical soil samples should be consistent with the soil area represented by the backbone agrochemical soil samples in the second soil survey, so as to compare the changes of soil nutrients before and after.

4. Sampling method and quantity: agrochemical soil samples are mostly collected by multi-point mixed soil samples, and the distribution range of sample points is not less than 3 mu (each place can be determined according to the situation). The depth and weight of soil taken at each point should be uniform, and the proportion of soil samples in the upper and lower layers should be the same.

5. Make sampling records: soil sample number, sampling location and latitude and longitude, soil name, sampling depth, previous crop and yield, sampling date, sampler, etc.