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Soil Sampling

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Soil analysis should be considered an essential tool in establishing a new orchard. Practical adjustments in soil pH, P, K, and Mg can best be made before trees are planted. Soil analysis in established orchards has some limitations and research has shown that results may correlate poorly with leaf-tissue analysis and tree responses. Nonetheless, a good soil sample can reveal much about the relative levels of Ca, P, K, and Mg in the soil as well as the need for lime. The greatest value in sampling soil in established orchards lies in the pH determination and the lime requirement. Soil acidity has a significant impact on the availability of nutrients. At soil pH values below 6.0 many of the essential major elements (N, P, K, Ca, Mg, and S) are less available. It is recommended that soil analysis be conducted at least once every three years. In blocks with previous problems, such as low pH, a soil analysis every year may be advised, at least until the problem is corrected.

Care should be exercised in collecting an orchard soil sample so it is as representative as possible of the orchard soil profile where the trees are growing. Remember that a soil analysis is no better than the sample collected. A shovel can be used to collect the sample, but a soil probe or soil auger specifically designed to collect a small core of soil is best and well worth the small investment especially if many samples will be collected. However, in rocky soils a shovel may be easier to use. The area collected per sample should be limited to a maximum of 5 acres. Avoid unusual spots in the designated sample area such as low ground with poor drainage, eroded areas, or similar areas that are uncharacteristic. If an area of the orchard appears to have a specific problem, collect a sample from the problem area and a second sample from an adjacent area where the trees exhibit normal growth. Also, use a soil survey map to ensure that only one soil type is collected per sample.

The best time to collect soil samples for orchard crops is mid-July through mid-August, however, since soil nutrient levels change slowly this sample can be collected almost anytime that is convenient (future samples should be collected during the same time period). A representative sample consists of several sub-samples collected from several locations within a block and mixed together to provide the final composite sample for testing. The number of sub-samples to collect depends on the size of the area being sampled: for areas of an acre or less, 7 to 10 sub-samples is sufficient; for plots as large as 10 acres, 20 to 25 sub-samples should be collected; for all other plots collect a minimum of 15 sub-samples. Remove the organic debris from the top inch of soil and collect a soil core or sample from the top 1 to 8 inch depth. It is recommended that a second sample be collected and submitted for analysis from the same site representing the 8 to 16 inch depth but this is not essential unless severe subsoil problems are suspected. Collect the sub-samples at random from representative areas within the designated orchard area. Crisscrossing through the orchard from one end to the other is a good technique. Collect the sub-samples only from within the tree rows under the tree canopy about midway between the trunk and the drip line of the canopy, not in the drive middles between the rows. Mix the sub-samples thoroughly; remove large stones, pieces of root tissue and other foreign material. Send the sample(s) along with the requested information sheet on site history and, if possible, include past lime/fertilizer applications.

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For more information on Orchard Soil/Plant Sampling contact us: 
 

Laboratory Location:

AgSource Laboratories - Bonduel, WI715-758-2178 bonduel@agsource.com 
 
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