Soil Testing August 24th, 2007
Estimated Nitrogen Release or ENR is a calculated estimate of how much nitrogen will be released through the growing season from the organic matter (O.M.) or humus-like materials. Therefore, as the % O.M. increases, so will the ENR.
This calculation is based on the “rule of thumb” that organic matter contains 5% nitrogen. The rate at which organic matter will decompose and release nitrogen depends on many factors, but those of greatest effect are soil type, moisture and temperature. Because of this we adjust the ENR for geographical region (zones are listed on Midwest report), soil type (see Table 1 in the Midwest Laboratories, Inc. Agronomy Handbook), and crop (warm season vs. cool season).
Soil Testing August 24th, 2007
1. Varied depth of sampling (Sample at tillage depth).
2. Combining unlike soil areas into one composite sample.
3. Combining soil areas with different past liming, fertilizer, or cropping histories into one composite sample.
4. Combining an insufficient number of sub-samples into composite from extremely varied or land-leveled fields.
5. Attempting to use single composite sample for too large an acreage.
6. Varying amounts of organic matter or undecomposed organic matter in sample.
7. Soft rocks in sample.
8. Forced drying of soil sample at high heat.
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Factors Effecting Irregularities in Soil Testing
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Soil Testing August 20th, 2007
In mineral soils, a 6 2/3″ plow depth is considered to weigh 2,000,000 lbs/A, but organic soils may average only 1,300,000 lbs/A. Organic soils by definition contain over 20% organic matter and may range up to 85%. To show this high organic matter a “combustible O.M. test” must be used. Tucas and Warncke have both made reports on organic soils. The following points will outline key agronomic considerations when working with organic soils.
1. Because of the extreme weight difference per volume of soil and the shrink incurred when drying, an average conversion factor of .65 should be used to convert the ppm test readings to lbs/A. Organic Soils Weigh Less than Mineral Soils
Soil Testing August 20th, 2007
1. Count leaves when the collar shows. Three Leaf Plant The round tipped leaf is No. 1 (1).
2. Corn has approximately 20 days food reserve in the seed (2).
3. The seed’s food reserve provides energy and supports the plant through the three leaf stage or about ten days after emergence. Within this time:
a. When the shoot hits light, the secondary root system and growing point will be about 1-1/4 - 1-1/2″ below the soil surface.
b. At the growing point, the primary ear has been initiated. The number of rows and approximately the first 14 kernels of each row are also determined.