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Topics : Soil Fertility for Forage Crops : Pre-Establishment



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Soil Testing

Soil test recommendations from the Penn State soil testing program are designed to gradually build the soil levels for phosphorus and potassium into the optimum range and then maintain them there by replacing the nutrients that the crop removes. A regular soil testing program should be followed where fields are sampled at least every three years or when the crop changes in the field. The soil test prior to establishment of a forage crop is especially important. A regular program like this along with application of the recommended nutrients as fertilizer or manure is critical in the crops prior to establishing a forage crop and should result in meeting the pre-establishment soil fertility goals. Details on calculating soil test recommendations are provided in ST-4 "Interpreting Soil Tests for Agronomic Crops", or recommendations can be estimated from ST-2 "Fertilizer Recommendation Table" both sent out with each soil test run by Penn State. This information is also available in the Penn State Agronomy Guide.

A crucial part of a good soil testing program is to take good soil samples. Table 2 gives the recommended guidelines for taking soil samples. Most of the errors associated with soil testing are a result of samples that are not representative of the fields being tested. Remember the recommendations can only be as good as the sample and the information supplied to the lab.

Table 2. Guidelines for taking soil samples.

  1. Sample at the right time. The best time to sample is in the fall.
  2. Take cores from at least 15 to 20 spots randomly over the field to obtain a representative sample. One sample should not represent more than 10 to 20 acres.
  3. Sample between rows. Avoid old fence rows, dead furrows, and other spots that are not representative of the whole field.
  4. Take separate samples from problem areas.
  5. Sample to plow depth in cultivated fields.
  6. Take two samples from no-till fields: one to a 6-inch depth for lime and fertilizer recommendations, and one to a 2-inch depth to monitor surface acidity.
  7. Sample permanent pastures to a 3- to 4-inch depth.
  8. Collect the samples in a clean container.
  9. Mix the core samplings, allow to air dry, and remove roots and stones.
  10. Fill the soil test mailing container.
  11. Complete the information sheet, giving all of the information requested.