RTN: What Does It Mean For Your Hybrids

The correlation is significant; heavy early spring rains cause nitrogen deficiencies. The graph above is data pulled from SE Minnesota over the years, and tracking the percent of tissue s amples that come back deficient, compared against April/May rainfall. The more rain we get in April/May, the more often we see deficient tissue N samples. That makes sense, as heavy rains early in the season move nitrates lower and lower, and the potential for denitrification increases along with it.

The map of MN displays rainfall received to date since April 1, 2018. Keep in mind, the average rainfall for the state is just shy of 6” in April and May combined. Parts of southern MN received 2-6” above normal amounts, aligning with a greater probability of a high amount of responsive/deficient tissue N amounts.

At this stage of the corn plants life, root growth is occurring exponentially, and the nitrogen demand is following a traditional constant uptake pattern. In a few short weeks, at V8, only about 20 pounds of uptake has occurred, and 50% of uptake comes between V10 & R1. During the V10 to V14 growth stages, corn requires the availability of 7.8 lb. N/day, meaning two-thirds of the total N plant uptake is acquired by VT/R1, with 1/3 left post-VT.

Risk of nitrogen loss from early spring rains is measured by the amount of time it takes from N to convert from ammonium to leachable nitrate-N (which is driven strongly by temperature and moisture). Highest risk applications include fall urea, fall urea with an N stabilizer, & fall anhydrous. The least risk is a split application of N in the spring with sidedressing, obviously, with its timing coinciding with the largest N demands.

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