A project has been initiated in Illinois with the purpose of sampling soils for measuring nitrogen, with the main interest being nitrate levels.
Funding for a statewide soil testing project is being provided by the Council for Best Management Practices, thus there will be no cost to producers and those who take samples.
Low corn yields and early death of the crop in dry areas of Illinois have resulted in a great deal of nitrogen–both from fertilizer and from mineralization of soil organic matter–still being in Illinois soils. Because soil microbes convert ammonium to nitrate over time, it can be expected that nearly all of this N is in the form of nitrate.
Nitrate is a form of N that plant roots can take up, but it is also a form that moves readily in the soil. Without roots in most fields to take up the nitrate, the nitrate in the soil now is subject to downward movement with water. If soil stays relatively dry between now and next spring, some of the nitrate may remain in the soil to be available for next year’s crop.
Knowing how much soil N remains in fields now will provide valuable information from both economic and environmental standpoints. To start to gather such information, this soil testing project has been initiated.
Dan Schaefer, director of nutrient stewardship for CBMP reported the program is tied to the Illinois “Keep it for the Crop” program. The emphasis for this soil testing is for fields that will return to corn in 2013, he noted.
CBMP is asking ag retailers and certified crop advisors to collect soil samples as the project needs those experienced in proper soil sampling and persons to be coordinators in having enough samples from areas of the state, although soil sampling by growers is not discouraged. Results as they come in will be placed on a map.
Knowing soil N present now might be used by farmers to decide what to do in fall N application. Does high levels of nitrate mean farmers will need less total fall and spring N application for the 2013 crop? Knowing how much nitrate remains in the soil next spring could help farmers to fine-tune N rates if corn in 2013 follows corn in 2012.
Soil scientists explain that if there is enough rainfall to get tile lines running, farmers can expect some of the nitrate to leave the field in drainage water, or to migrate below the root zone. In fields without tile drainage, wet soil conditions (while soil temperatures are above 50 degrees) can also result in conversion of nitrate to nitrous oxide or nitrogen gas, both of which will leave the soil. Knowing how much nitrate is present this fall can help farmers know how much loss there might be before corn or soybean roots next spring start taking up what N is left.
More information on the soil testing project can be found at www.KIC2025.org.