Soil Sampling for SCN.
Once a field is infested with SCN, soil samples do not need to be collected each year. Soil samples from these fields should be collected before SCN-susceptible varieties are grown again or once every 3 years if resistant varieties are grown in a rotation.
While soil samples for SCN may be collected at any
time, the ideal time to sample is as close to soybean harvest as possible
(see Why Do SCN Populations Fluctuate, page 9). SCN numbers tend to be
highest when the plants are almost mature to shortly after harvest. Sampling
Procedure for collecting samples:
Soil samples collected for soil fertility analysis can be split into 2 samples:
near harvest allows sufficient time for the nematode laboratory to process the sample and provides you with information and enough time for variety selection or choosing alternative crops for the next year.
Nematode diagnostic laboratories usually have special forms to be submitted with soil samples. Even if such a form is not available when you sample, you should provide the following information:
Large fields may be subdivided into sections and a single composite sample from the different sections submitted for analysis. If the crop row is identifiable, place the soil probe within 2 inches of the row when collecting the soil core. Placement of the soil probe is not important for samples collected from cultivated fields or fields where soybeans were drilled. The importance of getting a representative soil sample of the area under consideration (whole field, section of field, area where plants show symptoms of crop injury) cannot be overemphasized. The quality and condition of the sample determines the reliability of the results.
How to Deal With Hot SpotsSoil samples should be collected from the area between the damaged plants and the "healthy" plants. Do not collect the sample from the center of the affected area because these plants usually have severely stunted root systems that cannot support SCN. Thus, the sample may show that SCN numbers are low when in fact there are high numbers present in the areas where plants are "healthy."
1. Use a cylindrical soil probe to collect soil samples. Collect to a depth of 6 to 8 inches.
2. 10 to 20 soil cores should be collected from a 10-acre area of a field for a realistic estimate of the numbers of SCN. Larger fields should be subdivided and sampled separately before bulking the soil into a single sample.
3. If the crop row is identifiable, take each soil core near the row.
4. bulk the cores in a container and mix thoroughly.
5. Soil samples for SCN analysis should be placed in a plastic bag labeled with an indelible marker, and stored away from sunlight before submission to a laboratory.
6. Cushion soil samples with packing materials before shipping them to a laboratory.