An analysis from soil testing lab, Midwest Labs, includes levels of key nutrients that are essential for your plants’ proper development. For instance, the typical test will determine the current levels of phosphorus, calcium, potassium, magnesium, zinc and manganese in your samples.

Once the testing is complete, a recommendation will be made about the best type of fertilizer to use for the specific types of plants you intend to sow.

For traditional growing methods, a customized analysis of your garden or farm fields ensures that you won’t waste money on over-fertilization, or worse yet: do your plants physical harm by adding too many chemicals.

For organic growers, the test will suggest what nutrient minerals are lacking.  This will help you determine what organic mulch may be necessary.  You can use compost as an alternative to fertilizers. If you opt to use this option or the chemical option, a soil testing lab is the best resource you have to optimize the success of your crops and gardens.

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).

Midwest uses ENR in computing nitrogen recommendations so that we do not over apply nor under apply nitrogen to our crops. Questions sometimes arise as to how to explain the use of the ENR to the farmer. Following is an example of how one may explain its use regarding a corn recommendation:

A 150-bushel corn crop will remove 150 lbs. per acre in the grain and 75 lbs. nitrogen per acre in the stover meaning the total crop need is 225 lbs. nitrogen per acre. If we assume we have an organic matter level which will result in an ENR of 65 lbs. nitrogen per acre, we then have to supply the crop an additional 160 lbs. per acre through fertilizer or other plant foods. Realize that the Midwest nitrogen recommendation has already been adjusted using the ENR.

Let’s further assume that we have a nitrate level in the surface soil sample of 30 lbs. nitrogen per acre. Our nitrogen requirements would not be 130 lbs. Remember that nitrogen applications of fertilizer are not 100% efficient. Nitrogen is subject to losses by volatilization, immobilization, denitrification, and leaching. We can normally assume an efficiency factor of 60% to 70% with a preplant application. With an assumption of 70% efficiency, we would have a recommendation of 185 lbs. for 150-bushel corn.

150 bu./A X 1.5 =            225 lbs. nitrogen needed
                                    -65 lbs. ENR
                                     —
                                   160
                                   -30 lbs. NO3-N
                                     —
                                   130
                                  x 70 % N efficiency factor
                                     —
                                   185 lbs. nitrogen recommendation

As you split your applications of nitrogen, you reduce your risk of loss and increase your efficiency. If you increase your efficiency factor to 90%, you would only need 145 lbs. nitrogen. This is where adjustments can be made in nitrogen recommendations which are received from the laboratory.

Another adjustment in making nitrogen recommendations would be credit for the previous crop (legume). Remember that this nitrogen is in the crop residue and roots. These must be decomposed before the nitrogen is available. If you are planting a cool season crop following a legume, no adjustment should be made as time has not permitted crop residue to be decomposed. For corn following soybeans we suggest a 20-lb. N credit and 50 lbs. for a good stand of alfalfa.

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

2. Organic soils or peat “do not improve the amount of moisture available to the plant because of the higher wilting point and the marked decrease in volume weight of the soil.”

3. The Cation Exchange Capacity does not show that much difference from a mineral soil again because of the weight difference. The CEC of a muck may be five times greater than a loam soil but a fibrous peat will be about the same.

4. In most organic soils, the ideal water or soil pH range is 5.5 to 6.0. On organic soils, pH’s over 6.0 can reduce the availability of manganese, zinc, boron and phosphorus.

5. Organic soils contain large amounts of potential nitrogen. However, during a given growing season, only small amounts are mineralized into available “N”. How much is released in any year is governed by the nitrogen content itself, temperature, moisture, acidity and aeration, all of which affect soil microbiological activity. In the northern states, most organic soils respond to some nitrogen in the spring when soils are wet and cold.

6. Liming improves the availability of phosphorus in mineral soils but decreases its availability in organic soils that are low in iron and aluminum.

7. Organic soils contain low amounts of potassium. Unlike mineral soils, organic soils do not fix nor strongly adsorb potassium, so the nutrient is more mobile, especially if they receive excessive amounts of drainable water.

8. Salinity can be a problem, since organic soils often receive liberal rates of fertilizer. Critical salinity values are about twice those suggested for loam soils. Organic soils have some specific micronutrient problems. After testing and more specific information is in hand, your Midwest Laboratories representative will assist you in further interpretation.

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.

With these basic principles, let’s review some variations which can influence plant stands.
4. Planting too deep (4) places stress on seed food reserve and can relate to leafing out below the ground. If the shoot does emerge, this early stress may carry on to the harvest as a tall thin plant with a nubbin ear. Planting deeper does not move the secondary roots down; the mesocotyl (5) only becomes longer.

5. Planting too shallow (6) can move the secondary root system closer to the surface. Two primary concerns are:

1. The secondary root is closer to concentrations of surface incorporated chemicals.

2. If surface soils dry out, the young plant will show the classic stress symptoms of purple and/or yellowing. Planting in a depression when soils are mellow can result in the same symptoms and potential chemical stress as planting too shallow. If the depression is filled in by dragging, wind or water moving soil, it changes the relative position of the seed to the soil surface. As a result:

a. More stress is on the seed for reserve to push the shoot to the soil surface.

b. Visualize where chemicals are (herbicide or banded insecticides) in relation to the secondary root system which is 1-1/4 – 1-1/2″ below the shoot when it breaks the soils surface. The secondary root can be very close to herbicide and insecticide concentrations. Insecticides which are phytotoxic can increase the potential stress.

c. Under these conditions, you should expect to see hybrids react differently.