Urea is one of the most popular nitrogen fertilizer sources in Minnesota, but it can be trickier to manage than some other fertilizers because it has a higher risk of nitrogen loss via ammonia volatilization. It has been documented that spring application of urea can lead to sugarbeet stand reductions. Dry conditions in some areas of the state this year, especially on sandy soils, led to grower concerns about this issue. What does current research say about urea and sugarbeet stand loss?
What is the problem?
An ongoing study funded by the Sugarbeet Research and Education Board of Minnesota and North Dakota focuses on two areas: 1) Timing and rate of urea applications, and 2) Alternative products such as ESN and inhibitors marketed for urea. Stand reductions occur in both the northern and southern sugarbeet growing regions of Minnesota. While sugarbeet stand can be reduced by small rates of spring-applied N, typically the reduction is limited until rates of N exceed what is typically suggested to maximize production at a given site (see the U of M’s sugarbeet fertilizer guidelines). For example, at a field site near Renville this year, initial stands were 210 to 220 plants per 100 feet of row, and stands were reduced to around 160 plants per 100 feet of row when up to 210 lbs of N was applied in the spring before planting. (There was no impact of fall-applied urea on stand at Renville in 2023.) In past years, even though stand has been significantly reduced, there has been no significant reduction in root yield. Simply put, the sugarbeet plant adapts to stand loss, producing larger beets, which may not impact your operation’s profitability.Should all urea be applied in the fall?
Fall application of urea has a higher risk of nitrogen (N) loss than spring application. Despite potential stand reductions for spring application, the fact that there is no clear relationship between stand loss and a reduction in root yield suggests that spring application is still likely the best course of action for growers to limit N loss and maximize profitability. The effect of timing on root yield and quality is still being evaluated.Can the problem be managed with inhibitors or different urea products?
The current study also evaluates inhibitors and urea sources such as ESN. The data is currently inconclusive on whether inhibitors or ESN could reduce the risk for stand loss. Part of the reason for this is that the current research is comparing products at lower N rates, primarily focusing on yield effects. Application rates below the U of M guidelines have not been shown to greatly reduce stand, so it not likely that we will see whether inhibitors can help manage the issue in this study. Remember, our research has not seen a relationship between stand loss and root yield, so the added cost of an inhibitor or a product like ESN is likely not warranted.Are there any circumstances where some caution should be taken?
There could be some instances where a reduction in stand may be severe enough that some changes in management may be beneficial. For example, sandy soils that are dry may be at greater risk for stand loss. This study has not identified a point at which stand loss begins to impact yield. If growers are applying the suggested application rates of N, then stand loss should be minimal and not impact yield.Are other crops at risk?
None of the data we currently have on corn suggests that stand is reduced when higher rates of urea are applied. Corn is more tolerant to salt and ammonium near the seed than some other crops. For wheat and other small grains, too much N increases the risk for lodging, which can affect harvestable yield, but crop stands are less likely to be impacted. Urea is still one of the best sources of nitrogen that can be applied to crops.---
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