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Collecting A Sample

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General Aspects of Sample Collection

For whatever reason (a better yield for a corn crop, to stop your lawn from dying, the state requires it, etc.) you have decided that you need to have some kind of analysis done. If you are going to have it done, you should get the most for your time and money. You may consider that this is dependent on the test methods and how well the lab carries out these methods. Of course, in part, that is true. However, remember that laboratory analysis is our profession and Sunland goes to great effort with it's quality controls; calibrating instruments before every set of analyses and after every tenth sample; testing samples of known content (Purchased from U.S. Standards agencies) and much more. So the probability that you will get an incorrect answer from the laboratory is small. However, if in collecting soil for analysis you place it in a bucket that has recently contained fertilizer, I guarantee you that the results of the analysis on this sample will not reflect the true soil conditions. The point is, of course, that the way you collect the sample is one of the most important aspects of getting meaningful, useful analytical results.

There are two types of general sampling processes the first is the individual "point" sample that allows absolute analytical analysis values to be determined at the very spot where the sample was obtained. To use this sampling method to establish analytical values over an expanded area requires a very specific sampling plan established mathematically to insure that the final results will be statistically meaningful. Sunland will be pleased to help you establishing such a plan if this sampling method is required. The second general method is a composite sample. The composite sampling method requires that several samples be taken from the site of interest, these samples are then mixed and a portion is submitted for analysis. The composite sampling method is used most commonly for agriculture and landscape.

Though the composite method is similar in it's usage for agriculture (see - agriculture soil sampling) or landscape (see - landscape soil sampling) there are obviously differences in the amount of area to be evaluated. Similarly, analysis of plant leaves (see- plant tissue sampling) can readily be accomplished for agricultural crops or garden plants, but their functional utilization varies significantly. Water sampling for irrigation suitability does require some specific steps (see - water for irritation) and analysis of drinking water for microbiological purposes (see - water for microbiology) requires that you obtain a sterilized container from Sunland as well as following some very specific requirements.

Agricultural Soil Sampling


Collecting a soil sample for agricultural purposes generally has the advantage that there is a significant history available on the plot and that the soil is readily visible and accessible. Assuming generally uniform visual characteristics to the site a single sample can be representative of up to 40 acres. A minimum of 8 sub samples should be taken from the top 12 inches at varying areas of the field, mixed and approximately one pound submitted for analysis. Avoid unusual areas when obtaining a representative sample. Areas that show poor growth need to be sampled separately.

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Plant Tissue Sample

Plant tissue analysis is the optimal method for management of orchards, grapes and similar crops where the plants are maintained over many years. Problems with row or field corps can be rapidly diagnosed by the use of plant tissue analysis. Considerable data is available to provide indications when a specific nutrient is below, adequate or excessively present in these plants. Less information is available for horticultural plants, but very significant information can be realized by making direct comparisons between the analysis of normally growing plants and those having problems.

The rule of thumb for all plant tissue analysis is to take the forth leaf back from the growing tip of the branch. For a representative sample from a field or garden collect a leaf from different plants spread out over the entire growing area. For plants (individual or group) having a specific problem limit sampling to only the affected plants. To provide ample amount of tissue for analysis and a representative sample collect 20 leaves from plants with large leaves (i.e. walnuts, grapes, camellias) and 40 leaves from plants with smaller leaves (i.e. almonds, prunes, roses) Leaves collected should be placed in a paper bag to allow plants to dry. They need not be refrigerated and they should not be put in plastic or plastic lined bags (be sure to label bag).

The following is a list of some plants where the general rule of sampling (i.e. forth from growing tip) may be difficult to interpret.

  Alfalfa Upper 1/3 of plant 20  
  Asparagus Fern above 20 inches 20  
  Corn pre tasseling 1st developed leaf below whorl 20  
  Corn post tasseling Leaf opposite and under ear 20  
  Grape Leaf Petiole opposite bloom or cluster 20  
  Rice and other small grains Most fully mature leaf 20  
  Root Crops (carrots, beets.) Center mature leaves 40  
  Sugar Beet Petiole from youngest leaf to attain max size 20  


Landscape Soil Sampling


It is assumed that landscape samples will be collected from sites that are one acre or less and is suggested that a separate sample be collected for each acre to be landscaped. This "rule of thumb" stems from the typical unknown soil character, soil variability and lack of plant growth history of these sites. The most important point to remember for soil analysis is that ”the soil analysis can only be as good as the sample provided. Following these steps will provide you with a reasonable assurance of obtaining a representative sample for analysis.

In Tues Out Fri - In Fri. Oun Wed.

  1. Clean sampling tools and use clean plastic bucket for mixing sub-samples. Clean is emphasized because materials last in the bucket may show up in your analysis.
  2. The depth of the sample can be determined by a common sense rule ofthumb. Where are the roots of the plants going to be? Surface growing plants would have samples at 6 in. while trees or plants with deeper root systems should have samples taken from 12, 18, or 24 in.
  3. Take at 5-10 sub-samples in small areas (or even a pile of fill). Thoroughly mix these sub samples and submit about 1 pound for analysis.
  4. Avoid unusual areas when obtaining a representative sample. Areas that show poor growth need to be analyzed separately. Get the most from your analysis by taking the time to obtain a representative sample.

Compost Sampling


Compost Collection - The complex process of composting causes different rates of material degradation, heating and chemical release and can result in significant variation in the chemical composition in different regions of the pile or windrow. This happens even though the material is regularly turned and mixed. To acquire a representative sample it is suggested that sub-samples are taken approximately every four feet along the windrow. At each sample site an equal size sample (approx. 1 pint) should be collected from near the surface, at he center of the pile or windrow and a third sample about half the depth to the center. Mix the sub-samples from approximately 20 feet of a windrow in a clean five gallon bucket. Submit about a quart of the mixture in a 2 quart plastic bag.

Water Agricultural Suitability Sampling

It is important that water to be tested is representative of the source and is not contaminated by sediment or rust from the pipes at the site of collection. Therefore, fully open the valve and allow the water to flow for 3 to 5 minutes. Fill and empty the sample container three times to completely rinse out the container. Fill the container (approximately one pint) and submit for analysis. If quantitation of varying forms of nitrogen (total nitrogen, ammonia, nitrate) are of importance, the sample should be kept cool and submitted to the lab on the same day as collected.

Water Microbiology Sampling

The sample must be collected in a ”STERILIZED" container (available from Sunland). The volume of sample should be sufficient to carry out all tests required, preferably not less than 100 mL. When the sample is collected, leave ample air spacein the bottle (at least 1 inch) to facilitate mixing by shaking, before analysis. Keep sampling bottle closed until it is to be filled. Remove cap as a unit: do not contaminate inner surface of cap and neck of bottle. Fully open the water valve and allow the water to flow for 3 to 5 minutes. Fill container without rinsing, replacing cap immediately. Accompany samples by complete and accurate identifying and descriptive data. ” Samples will not be accepted for analysis be accepted for analysis without the following information: Sampler's name, Sample Location Identification, Time and Date sampled.



Potable (Drinking) Water

Open tap fully and let water run to waste for 3 or 5 min. or for a time sufficient to permit clearing the service line. Reduce water flow to permit filling bottle without splashing. If tap cleanliness is questionable, apply a solution of sodium hypochlorite (household bleach) to faucet before sampling; let water run for an additional 2 to 3 min after treatment. Do not sample from leaking taps that allow water to flow over the outside of the tap. In sampling from a mixing faucet remove faucet attachments such as screen or splash guard, run hot water for 2 min. then cold water for 2 to 3 min. and collect sample as indicated above. In drinking water evaluation from distribution systems, collect samples of finished water selected to assure systematic coverage during each month. Carefully choose distribution system sample locations to include dead-end sections.

Waste Water


In collecting samples directly from a river, stream, lake, reservoir, spring, or shallow well, obtain samples representative of the water that is the source of supply to consumers. It is undesirable to take samples too near the bank or too far from the point of drawoff, or at a depth above or below the point of draw off. Take samples from a river, stream, lake, or reservoir by holding the bottle near its base in the hand and plunging it, neck downward, below the surface. Turn bottle until neck points slightly upward and mouth is directed toward the current. If there is no current, as in the case of a reservoir, create a current artificially by pushing bottle forward horizontally in a direction away from the hand. Remove from the water, pour off excess and cap.

Sample Transportation

If samples cannot be processed within 1 h after collection, use an iced cooler for storage during transport to the laboratory. If it is known that the results willbe used in legal action, employ a special messenger to deliver samples to the laboratory within 6 h and maintain chain of custody. Analysis of drinking water must be initiated within 30 hours from collection and analysis of waste water within 6 hr.