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Big Rains, Big N Worries (06/23/16)

There have been big rains in large areas of North Dakota, particularly north of Rt 2. Six inch rains in a few days, followed by 6-7 inch rains in a few days, 10-15 inches total over a few weeks.

Big Rains, Big N Worries

There have been big rains in large areas of North Dakota, particularly north of Rt 2. Six inch rains in a few days, followed by 6-7 inch rains in a few days, 10-15 inches total over a few weeks. Corn is sitting in either standing water or saturated soils. N loss in high clay soils averages about 1.5% nitrate N per day under saturated soil conditions. In eastern North Dakota, loam soils are also at risk to some level of denitrification, as well as leaching. Corn in many fields is yellowing on the bottom, with symptoms similar to N deficiency. Since many of these fields are V6-V8, there is still time to for the corn to recover. If the nitrate has simply moved below the present rooting depth, the roots could catch up to it later on. It is important to wait a few days for the field to dry somewhat and the water content of the soil to lower. When this happens, some of the corn will begin to green up again. Corn that does not green up may need a late side-dress application, either by streaming UAN/ATS between the rows, or applying up to 46 pounds N/acre as urea treated with an NBPT or NBPT product (Agrotain or its siblings or Limus) over the top. If S is also suspected to be a problem due to leaching, 10 pounds S per acre as ammonium sulfate can also be applied over the top. To confirm N or S deficiency, a paired plant sampling in green areas compared to the distressed area can be diagnostic.

Dave Franzen

NDSU Extension Soil Specialist

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