The most important aspect of a soil, water or tissue analysis is knowing how to take representative samples. Without a proper begining, the results will be difficult to interpret. AgSource Harris has prepared the following instructional sampling guides. If you have any questions about sampling procedures or need sampling supplies, simply contact us.

A soil test is not only the foundation for beginning a well-planned fertility program; it is also the tool to measure its success on a long term basis. As fertilizer is applied and crops are harvested, the soil test indicates whether the soil fertility is increasing or decreasing. In order to properly monitor these changes field histories need to be accumulated. History data should include: previous soil test data, crop rotation and yields, fertilizer and amendment application times and rates, climatic data, soil temperatures, seasonal rainfall and soil moisture conditions. Over a period of years, these histories are a valuable resource in developing a clear understanding which factors have the greatest influence on yields.

In order for a soil test to be an effective monitoring tool, sampling procedures need to be consistent from one year to the next. This is where field histories come in. Factors such as sample depth, area represented, time of year, number of sub-cores and sampling equipment should be the same each time the field is sampled.

Most surface samples are taken from a depth of 0 to 6 to 0 to 8 inches. This is where management of fertilizers and soil amendments occurs, meaning this is the volume of soil that will be affected by a grower's management. The exception to this is the mobile nutrient which has the ability to move with the soil water: nitrate, sulfate and chloride. In addition to the surface it is recommended that these mobile nutrients also include a profile depth of 6 to 24 or 6 to 36 inches. These profiles need to be collected into a separate bag with the depth labeled.

Of all the factors affecting consistency of a soil test system, sample depth has the greatest influence. Below is a table demonstrating the affects of a tillage system and sample depth on phosphorus soil test values:

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Soil Sampling Depth and its affect on Soil Test Phosphorus (Bray I-P)

Stratification in Reduced Tillage

For sampling in no-tillage systems maintaining sample depth is even more important. Immobile nutrient (such as phosphorus) build on the soil surface with broadcast fertilizer applications. At some point in time it becomes important to determine the degree of stratification. It is suggested that a sample unit/area be used as a test, instead of a 0 to 6 inch sample depth, perform a split sampling of 0 to 3 inches and also from 3 to 6 inches. This split sampling allows the determination of stratification. If the second depth (3 to 6) is 50 % of the surface depth (0 to 3), significant stratification has occurred. Further, broadcast applications without tillage will continue the process. It would be advisable to recommend a deep tillage and begin the no-till process over.

Representative Area Sampling

Conventional Sampling System

Several options are available for determining how to divide field/fields into individual soil samples. If the field is less than 20 acres the whole field can be made as one sample. If greater than 20 acres then multiple samples are required. Topography, soil type or even divisions can do this division. It is important to remember that unusual areas (farmsteads, fence rows, ponded areas, blowouts, etc.) need to be avoided or sampled separately. Old farmsteads are still apparent decades after they are abandoned.

When sampling, 15 to 20 sub-cores are needed for providing a representative sample, more would be even better. In addition the laboratory needs at least 8 ounces or 1 pound of material in order to perform all analysis.

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GRID Soil Sampling

Grid soil sampling involves dividing the whole field into small equal sized grids. Most grid sizes comprise 2.5 up to 5 acres. The soil cores from each grid are collected either from the center point or from random points through out the grid cell. A minimum of 10 cores is needed in order to provide the laboratory with enough soil to perform analyses.

Time of Year to Sample

The time of year (Early fall - vs. - spring) can have an affect on analytical results. For monitoring, it is recommended that samples be collected during the same season: late fall, winter, spring and summer. Do not rotate your sampling schedule.

Research conducted at the University of Wisconsin

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Sample Handling

Proper handling of the sample is important to maintain the integrity of the soil. Soil is a biologically active material, this activity continues even after the sample has been collected. It is necessary to collect and ship no later than the next day. If storage is required, three options are available; dry the soil with low heat (not greater than 120 F), store in a freezer or at least refrigerate. These processes will slow down or stop the biological activity, preserving sample integrity.

Sample Submittal Forms

To streamline the laboratory's handling (to assure fast turnaround) of the received samples include laboratory submittal forms. Laboratory supply order form and submittal forms (sample sheets) are available at AgSource Harris.

Essential information includes:

- Your company name and address (this should preprinted from the laboratory)
- Grower Name
- Sample Identification
- Crop and yield goals
- Previous crop
- Desired test options

AgSource Harris provides complimentary sampling supplies, simply contact us.

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Analysis included in the AgSource Harris Irrigation Suitability test package includes:

Water pH, Hardness, Bicarbonate, Carbonate, Electrical Conductivity (Ecw), Total Dissolved Solids, Sodium, Chloride, Boron, Sodium Absorption Ratio, Nitrate, Phosphorus, Potassium, Magnesium, Calcium, Sulfate, Manganese, Iron.

STEPS FOR COLLECTING WATER SAMPLES FOR AN IRRIGATION-SUITABILITY TEST:

• A clean plastic container should be used. Rinse the bottle (including the lid) several times with the water to be tested. If desired, the laboratory will supply sampling kits, including clean plastic bottles.
• To reflect what the water quality is at the time of application, collect sample from the pumping station or within the irrigation system.
• If a system of irrigation wells (ground water) are being used, sample each well separately. This will qualify the water specifically from each well. (This is important if pumping into a holding pond.)
• When collecting sample from the irrigation system, let water run for two to three minutes before collecting the sample. (This will purge static water from the system.)
• When sampling from a pond, collect water from the pumping station. If possible, DO NOT collect the water from the side of the irrigation pond, sediment will act as a contaminant.
• Fill bottle and eliminate all head space. Be sure lid is tight so that samples do not leak out during transit. Laboratory needs at least 100 ml (about 6 ounces) of water.
• If using glass, be sure to use adequate packaging.
• If possible, collect and ship sample/samples the same day.
• Be sure bottles are clearly identified and necessary paperwork is completed before shipping.

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The value of plant analysis for diagnosing and monitoring the nutritional status of plants hinges largely on the care that is taken in collecting, handling, and analyzing the gathered plant material. Unreliable and misleading interpretations will occur unless proper steps are taken to minimize errors from each of the above tasks. For this reason standard collection procedures are essential for success. Below are steps that will help standardize the collection and handling processes:

STEPS FOR COLLECTING:

• As with soil sampling, select the area/areas to be sampled. Each unit should not represent more than 20 acres. A randomized pattern is essential for determining the average. At least 20 separate plants should be sampled, this is necessary for obtaining a true average as well as getting the laboratory enough material to perform the analysis. For petiole sample at least 50 plants are needed to collect enough material.
• Determine the proper plant part. As a general rule, you want the collect the leaf blades or petioles from the most recently mature leaves. Avoid very mature leaves or not fully developed leaves. The attached diagrams include sampling schemes for several common agricultural crops. For a more compete listing of crops it is advisable to call the laboratory for specific directions.
• Avoid sampling from unusual areas. For monitoring fertility trends it is important to look at only healthy or actively growing areas. Chlorotic or slow growing areas will have inconsistent nutrient concentrations, providing false conclusions. If this is the major concern, sample separately and compare the results with the result from the "healthy" areas.
• Do not sample from stressed areas: water stress, heat stress or water logged.
• If sampling from a mixed crop (alfalfa/grass forage), sample each species separately.
• Collect samples from the same time of day each time you sample. Nutrient values will change as the day progresses.
• Soil adhering to the plant tissue needs to be removed, by brushing with a paper or cloth towel.
• Sample may be washed with deionized water. However, do not soak the samples, water-soluble nutrients (nitrate, potassium, sulfate) will be leached away, providing low reported values.

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Handling and Shipping Instructions:

• If possible, collect the samples and ship to the laboratory the same day. These samples are still biological active, storage at room temperature will have an affect on the reported values. If immediate shipment is not possible, store samples in a refrigerator or dry samples with low heat (less than 160 F).
• Collect samples in a paper or cloth bag (DO NOT use plastic) and loosely pack into a shipping box. To avoid molding, samples need to be allowed to breath during transport.
• Completely fill out laboratory paper work. Essential information includes; grower name, crop type, unique sample identification, date sampled and analysis package. Laboratory information sheets are available at the AgSource Harris web site, www.ag.mdsharris.com.
• Ship samples to laboratory as quickly as possible.

AgSource Harris provides complimentary sampling supplies, simply contact us.

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	Cotton: following first bloom collect the petiole or leaf blade of the youngest fully mature leaf.
	Cereals: during tillering collect youngest early leaf blade (YEB) or basal stems.
Top	Pasture legumes: until early flowering collect the youngest open leaf blades.
Top	Grape Vine: at flowering collect a petiole (leaf stalk) from a basal node opposite a bunch.
	Deciduous fruits: in mid-summer collect a leaf from a mid-shoot position.
	Corn: from tasselling to pollination collect leaf blades below and opposite the cob.

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