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Adapted from Alberta Environment: http://www1.agric.gov.ab.ca/$Department/deptdocs.nsf/all/agdex1341
Importance of Soil Sampling & Testing Soil testing provices an index for the nutrient availablity in soil and is a critical step in nutrient management planning. Soil sampling technique, timeing and sampling and type of analysis need to be considered for accurate results. The biggest problem in the effective use of soil testing is proper and representative sampling. Proper soil sampling will provide accurate soil test results and reliable nutrient recommendations. The following information is offered to answer special questions concerning soil sampling. Further information and guidance can be obtained by contacting your fertilizer dealer, private laboratory or crop advisor. When to Sample Where to Sample Random soil sampling is the traditional approach that works for uniform fields with little variation. The managed random sampling technique samples from areas identified as average production areas. This approach is different from random sampling, which provides an average of all cores taken throughout your field. Managed random sampling is recommended if you cannot identify a dominant production area on your field. Benchmark sampling is recommend for fields with more variability (hills, pot holes, etc.). Benchmark sampling reduces the inherent variability of a field by reducing the area sampled. A small area (generally about - of an acre) representing the majority of the field is sampled the same number of times as in random sampling. This is the reference area from which fertilizer recommendations are made. The benchmark site should be marked with a global positioning system (GPS) or other means so that one can return there for subsequent years' sampling. Sampling from the same area will reduce sampling variability and create a better picture of year-to-year changes. Creating more then one benchmark is recommended if you cannot identify a dominant producation area on your field. Soil Variability also plays a key role: as soil components will retain or release nutrients from leaching, plant uptake, and hydraulic flow differently (i.e. sandy soil transports nutrients much quicker (and therefore holds nutrients less) than a higher clay soil. Dividing a field into management zones allows for an understanding of different conditions within a field. This approach is particularly effective in rolling and hummocky landscapes. For example, a large depression may be a very productive area, but a separate soil test may indicate it can be optimized with a higher rate of nitrogen than the benchmark is indicating. While most producers do not have variable rate capabilities, rates can often be easily increased through other adjustments. When picking a benchmark area, use observable features such as soil color and landscape to identify where different soil types occur. Select a site that has characteristics similar to most of the field or the dominant soil type. Often, the best time to identify different soil characteristics is through crop development. At the beginning of the growing season, differences in crop establishment and vigor can be seen, making a represntative location easier to pick out. Other ways of selecting postential benchmark sites include the use productivity, yield, aerial and/or topographic maps. The benchmark process can be further extended by establishing a couple of benchmark areas in different areas that allow customization of fertilizer rates. by identifying a primary benchmark area, and a secondary benchmark area and perhaps even a tertiary benchmark area, a fine-tuned fertility management strategy can be achieved even without variable rate technology. Each field (with the same crop and management history) must be sampled separately. Size up each field and observe variations in yield and crop growth, texture, color, slope, degree of erosion, drainage and past treatment. Sizable areas of fields where growth is significantly different from the rest of the field should be sampled separately. Avoid unusual areas such as dead or back furrows, old straw, hay or manure piles, waterways, saline spots, eroded knolls and old fence rows. Select 15 to 20 sampling sites representative of the portion of the field to be tested .Sample tools and methods Place cores in clean pails or bags then mix cores taken from the same depths, crushing lumps in the process. Keep samples taken from individual depths separate from one another. Soil samplers may be available on request from fertilizer dealsers, private labs or crop advisors. Many fertilizer dealers offer soil sampling services. Preparing and submitting samples Central Labs recommends soil samples of minimum 1.5 cups (350mL). A clean, plastic bag (Ziploc or any comparable brand) is preferred. You MUST label each sample with your name, address, postal code, field and depth from wich the sample was taken. Central Laboratories has two packages available for soil nuturients. 1) Soil Chemistry: a saturated-paste analysis will report the following: 2) Soil Texture Analysis: Central Laboratories Ltd. provides only analysis of the parameters within the scope of an associated package, unless prior arrangments have been made.
We CAN NOT, legally, provide interpretations on nutrients applications.
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