Agronomic Crops

Enclosures

• ST-2 Fertilizer Recommendation Table - Guidelines for making recommendations for other crops and for adjusting for a different expected yield.
• ST-4 Interpreting Soil Tests for Agronomic Crops–Explains the soil test report and provides additional information on the recommendations.

Soil Nutrient Levels

Soil nutrient levels are given as parts per million (ppm) elemental P, K, and Mg. As a rule of thumb to convert ppm to lb/A multiply ppm x 2. The elemental results in lb/A can be converted to oxide forms using the following conversions: P x 2.3 = P₂O₅ , K x 1. 2 = K₂O, Mg x 1.6 = MgO

Recommendations

N, P, and K recommendations are made for three crop years on this field. New samples should be taken after 3 years. The recommendations for the 2nd and 3rd year assume that the earlier recommendations were followed. These recommendations are made based on the results of the soil test and the information provided with the sample. If you think that there is an error on the report, contact the lab at the address on the front of the report. Tables that can be used to adjust or change recommendations for all crops based on the soil test can be found on this site.

Limestone Recommendations

The recommended limestone application should be adequate for 3 years. Limestone recommendations are based on 100% calcium carbonate equivalent limestone and assume “Fine-sized" limestone with 95% passing 20 mesh, 60% passing 60 mesh and 50% passing 100 mesh. Use “ST—2 Liming Materials Conversion Table (enclosed) to adjust for limestone quality. Also see Soil Acidity and Aglime

Magnesium

Only one Mg recommendation is made for three years. Magnesium is most economically applied by using a limestone containing Mg. Low Mg levels in soils may result in low Mg levels in forage crops especially if a significant amount of N and/or K fertilizer is applied. This can result in potentially fatal grass tetany in animals. Use caution if grazing. Apply the recommended Mg and be sure your feed rations are properly balanced.

Starter Fertilizer

Starter fertilizer is important to get a corn crop off to a good start when planting in cold, wet conditions. However, on optimum or higher testing soils, as planting dates get later and soils warm up, the benefit from starter fertilizer goes down. An N only starter is often adequate when soil test levels are above optimum. The correct material, rate, and placement for starter fertilizer are critical to be effective. See Starter Fertilizer

Nitrogen

Nitrogen recommendations on this report are not based on a soil test. They are based on crop requirements for the expected yield of the crop to be grown. The pre-sidedress nitrate soil test (PSNT) and the Chlorophyll meter test are both available for improving nitrogen recommendations on corn especially when manure is being applied. See: Pre-sidedress Soil Nitrate Test for Corn and The Early-season Chlorophyll Meter Test for Corn. For optimum efficiency, N should be applied as close to the time of crop need as practical. For corn apply 50–90% of the N when the corn is 10-20" tall. For winter grains apply the N in the spring prior to growth stage 5. For forage grasses split the recommended N for each cutting.

Manure

Manure is a very important part of a fertility program. Manure applications may supply all or most of the nutrients recommended and in some cases may apply significantly more than the crop requires. Manure nutrients should be taken into account in developing your fertility program. For details on how to do this see the Penn State Agronomy Guide. Manure analysis kits are available through your county Extension office.

Very High Soil Test Levels

Very high soil test levels should be avoided as much as possible. High soil nutrient levels might not only represent an economic loss but they may also indicate potential crop, animal or environmental problems.

Very high pH can result in micronutrient deficiencies and may affect the activity of some pesticides resulting in injury or poor pest control.

Very high phosphorus levels in the soil may lead to crop production problems especially with no manure and may result in potentially harmful P loss to the environment. Best management practices may be necessary to reduce the potential for environmental problems with P.

Very high potassium levels in the soil can lead to nutrient imbalances in forage crops which can cause serious health problems in animals. Use caution when grazing forage crops, especially if the soil magnesium is not also in the high range. It may not be possible to correct these soil imbalance in the short term. Feed rations must be balanced accordingly.

Zinc, Copper and Sulfur Results

Normal ranges for zinc (Zn) copper (Cu), and sulfur (S) in Pennsylvania soils are listed below. These are not used to make recommendations but rather to identify potential deficiencies of Zn and S or toxicity of Cu. While Zn and S deficiencies are not common in PA, they may occur on soils testing below the normal range. Zn deficiencies are more likely to occur when soil levels are low and soil pH 7.0 or higher, especially on lighter soils. Recent research in Pennsylvania on sulfur fertility suggests that when the Mehlich 3 S level is below 15 ppm, there is an approximately 50% chance that yield will increase by adding S fertilizer. When Mehlich 3 S levels are above 15 ppm, S is usually adequate and there is a very low chance of a yield increase from adding S fertilizer. Both Zn or S deficiencies should be confirmed with plant analysis. Cu toxicity may occur at levels testing well above the normal range, but have not been observed in Pennsylvania in agronomic crops even on soils testing 2 to 3 times above the normal range. For additional information, see ST4.

Distribution of Soil Test Results

Summaries of soil test results may be used in educational programs. However, individual results will not be released outside of Penn State without permission of the client. Electronic copies of your results are available to you, contact the lab for more information.

For additional information on these topics please see the current Penn State Agronomy Guide or this site. This soil test is part of an ongoing research and extension program of Penn State. If you have any questions or comments about this program or would like copies of publications referenced here, please contact your county Penn State Extension Educator.