Attachment H - Agronomy Handbook~10.pdf

Attachment H Agronomy Handbook

State of Illinois IFB Contract: Agronomy Handbook V.23.4

The Agronomy Handbook can be accessed at the following web address:

http://extension.cropsci.illinois.edu/handbook/.

Relevant information from the Handbook related to soil levels is also attached here in “Attachment H”.

http://extension.cropsci.illinois.edu/handbook/

Contract: Agronomy Handbook V.23.4

IDNR Ag Lease - Min Soil Test Levels for Ag Fields

Soil pH Maintenance Levels – 6.2 goal, 6.0 – 6.5 acceptable

Phosphorus (P) Maintenance Levels

Soil P Supplying Regions

Units High Medium Low

Minimum Soil Level 30 40 45 lbs/ac

Recommended Levels Corn/Beans 40 45 50 lbs/ac

Recommended Levels Wheat/Oats 60 67.5 75 lbs/ac

Potassium (K) Maintenance Levels

Soil K Exchange Capacity Regions

Units High (>12 mEq) Low (<12 mEq)

Minimum Soil Level 300 260 lbs/ac

Above with No Addition 400 360 lbs/ac

Levels >100 lb. above Min Replace Yield K Replace Yield K lbs/ac

Levels Below Minimum Replace Yield K + Build to Min

• Adjustments needed based on location and timing of sampling. See Attachments.

Contract: Agronomy Handbook

Phosphorus (P) Maintenance Levels

Illinois Agronomy Handbook (Ch 8, 100)

Minimum soil test levels required to produce optimal crop yields vary depending on the crop to be grown and the soil’s P-supplying power. Near maximal yields of corn and soybeans are obtained when levels of available P are maintained at 30, 40, and 45 pounds per acre for soils in the high, medium, and low P-supplying regions, respectively. Since these are minimal values, to ensure soil P availability will not restrict crop yield it is recommended that soil test results be built up to 40, 45, and 50 pounds per acre for soils in the high, medium, and low P-supplying regions, respectively. This is a practical approach because P is not easily lost from the soil, other than through crop removal or soil erosion. To compensate for the higher P requirements of wheat and oats, it is suggested that 1.5 times the amount of expected P removal be applied prior to seeding these crops.

When soil test levels are between the minimum and 20 pounds above the minimum (40 to 60, 45 to 65, and 50 to 70 for the high, medium, and low P-supplying regions, respectively), apply enough to replace expected removal by the crop. When soil test levels are below the desired values (40, 45, and 50 for the high, medium, and low P-supplying regions, respectively), it is suggested that enough fertilizer be added to build the test to the desired goal and to replace what the crop will remove (as described in the previous paragraph). At this test level, the yield of the crop will be affected by the amount of P applied that year.

On average, Illinois soils require 9 pounds of P2 O5 per acre to increase the P1 soil test by 1 pound. The recommended rate of buildup for P is thus nine times the difference between the soil test goal and the actual soil test value. For a typical 4-year buildup program, divide the rate by 4 to determine the annual rate. Because the 9-pound rate is an average for Illinois soils, some soils will fail to reach the desired goal in 4 years with P2 O5 applied at this rate, and others will exceed the goal.

Potassium (K) Maintenance Levels

Contract: Agronomy Handbook

Illinois Agronomy Handbook (Ch 8, 103)

Soils with a CEC less than 12 milliequivalents per 100 grams are classified as having low capacity, while soils with values equal to or greater than 12 milliequivalents per 100 grams are considered to have high capacity. Tests on soil samples that are taken before May 1 or after September 30 should be adjusted downward as follows: subtract 30 for the dark-colored soils in central and northern Illinois; subtract 45 for the light-colored soils in central and northern Illinois and for fine-textured bottomland soils; subtract 60 for the medium- and light-colored soils in southern Illinois.

Minimum soil test levels required to produce optimal crop yields vary depending on the crop to be grown and the soil’s CEC. As with P, the only significant loss of soil-applied K is through crop removal or soil erosion, so to ensure that K availability will not limit crop yields it is recommended that soil test levels be slightly higher than that required for maximum yield. For corn and soybean, it is recommended to have 260 and 300 pounds of exchangeable K per acre for soils in the low and high CEC regions, respectively.

No K additions are suggested if test levels are above 360 and 400 for the low and high CEC regions, unless crops that remove large amounts of K (such as alfalfa or corn silage) are being grown. When soil test levels are between the minimum and 100 pounds above the minimum (260 to 360 and 300 to 400 for the low and high capacity, respectively), apply enough to replace what the crop to be grown is expected to remove using values from Table 8.6. When soil test levels are below the desired values (260 and 300 for the low and high capacity, respectively), it is suggested that enough fertilizer be added to build the test to the desired goal and to replace what the crop will remove (as described in the previous paragraph). On average most Illinois soils require 4 pounds of K2 O per acre to increase the K exchangeable soil test by 1 pound. The recommended rate of buildup for K is thus 4 times the difference between the soil test goal and the actual soil test value. For a typical 4-year buildup program, divide the rate by 4 to determine the annual rate.