2009-11-30_PERMIT FILE - C1981038 (5)

Home Browse Search

Volume 7 Exhibit 5 • 0 Quick Facts... A quality fertilizer recommen- dation depends on a quality soil sample. A composite soil sample should represent a uniform field area. Use a systematic sampling scheme and a minimum of 15 subsamples throughout the field, regardless of acreage. Sampling depth depends on the crop and the tillage depth. Sample most fields every year for nitrate analyses. Thoroughly air dry all soil samples within 12 hours after sampling. C6 11104, 0 niversity Cooperative Extension © Colorado State University Cooperative Extension. 6/97. Reviewed 2/03. www.ext.colostate.edu C R O P S E R I E S SOIL Soil Sampling no. 0.500 by J.R. Self and P.N. Soltanpour I Careful soil sampling is essential for an accurate fertilizer recommendation. A sample must reflect the overall or average fertility of a field so analyses, interpretations and recommendations accurately represent the nutrient or mineral status of the soil. An accurate evaluation of soil nutrient levels will result in more efficient fertilizer use, which can increase yields, reduce costs and potentially reduce environmental pollution. Consider each of the following before obtaining a soil sample: 1. field area (acreage) per sample, 2. sampling procedure, 3. sampling depth, 4. when to sample, 5. sampling tools, 6. sample handling, 7. information form, and 8. handling and mailing. Field Area A composite soil sample should represent a uniform field area. Each area should have a similar crop and fertilizer history for at least the last two years. Soil characteristics (color, slope, texture, drainage and degree of erosion) should appear similar. Exclude small areas within a field that are obviously different. These can be sampled separately if they are large enough to warrant special treatment. The field area represented by a single composite sample should be no more than 40 irrigated acres or 100 dryland acres. Fewer acres is better. Sampling Procedure Use a systematic sampling scheme. Grid the area in your mind's eye (it is not necessary to measure it) and sample once within each grid. Obtain an accurate nutrient evaluation of a field site with 15 to 20 surface subsamples per 40 acres and six to eight subsurface cores. Mix these subsamples thoroughly and save 1 pint for analysis. This pint mixture is the composite soil sample. In some cases, the number of subsamples may be limited by time constraints or availability of labor. Keep in mind, however, that fewer subsamples result in less accuracy in evaluating the nutrient or mineral status of the soil. Sampling Depth Take the surface sample to tillage depth. For perennial pastures or hay crops (cases where the soil is not annually mixed), sample to 4 inches deep. Be sure to separate and discard surface litter. Take deeper samples (subsoil) for 7R-51 nitrate - nitrogen (NO N) analysis where the nitrogen (N) fertilizer R"90mved 30 - All) V•201