Nutrient movement off frozen and snow-covered soil
Snow has now fallen throughout much of Illinois, and temperatures have dropped going into the last weeks in 2019. With the recent Illinois Nutrient Loss Reduction Strategy biennial report highlighting P and N levels in Illinois waterways, this is a good time to review the application of nutrients on frozen and/or snow-covered soils.
Last spring, after a short and often-muddy fall fertilizer season, a considerable amount of fertilizer—mostly P in the form of DAP or MAP and K as KCl—was applied during the first week of March when the soil surface was frozen. Between March 3 and March 8, 2019, minimum air temperature averaged less than 15 degrees F, and maximum temperature averaged less than 30 degrees over most of Illinois. This was one of the few times last winter when soils were frozen and there was little or no snow; and many took the opportunity to apply P and K.
Unfortunately, an inch or more of rain fell over most of Illinois south of I-80 followed fertilizer applications on frozen soils in early March 2019. Most of this rain fell during the day on March 9, and as evidenced by the rapid rise in streams and rivers, a great deal of this rainfall ran off the (then-frozen) soil surface.
As part of the ongoing water monitoring that IFCA conducts within their Keep it 4R Crop Program, several samples of water moving out of fields after this rainfall event were collected. In fields where P and K had not been applied recently, average levels of chloride, nitrate-N, ammonium-N, and phosphate-P were 2.3, 0.7, 0.1, and 0.3 ppm, respectively. We expect to see such low values, since these nutrients don’t tend to remain on or near the soil surface during the winter.
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Last spring, after a short and often-muddy fall fertilizer season, a considerable amount of fertilizer—mostly P in the form of DAP or MAP and K as KCl—was applied during the first week of March when the soil surface was frozen. Between March 3 and March 8, 2019, minimum air temperature averaged less than 15 degrees F, and maximum temperature averaged less than 30 degrees over most of Illinois. This was one of the few times last winter when soils were frozen and there was little or no snow; and many took the opportunity to apply P and K.
Unfortunately, an inch or more of rain fell over most of Illinois south of I-80 followed fertilizer applications on frozen soils in early March 2019. Most of this rain fell during the day on March 9, and as evidenced by the rapid rise in streams and rivers, a great deal of this rainfall ran off the (then-frozen) soil surface.
As part of the ongoing water monitoring that IFCA conducts within their Keep it 4R Crop Program, several samples of water moving out of fields after this rainfall event were collected. In fields where P and K had not been applied recently, average levels of chloride, nitrate-N, ammonium-N, and phosphate-P were 2.3, 0.7, 0.1, and 0.3 ppm, respectively. We expect to see such low values, since these nutrients don’t tend to remain on or near the soil surface during the winter.
Click Here to read more.