Mid-Season Nitrogen Management in Pumpkins – Vegetable Crops Hotline

Mid-Season Nitrogen Management in Pumpkins

​Pumpkins are off to good start and vines are starting to run, which means it is time to think about making a sidedress application of nitrogen. Typically, I recommend to split nitrogen applications half preplant and half sidedress. This is especially beneficial given all of our rain this season. If you relied on preplant N alone, with all of the rain, you may very well have lost almost all of your nitrogen with plants just now starting to set fruit. In my personal scenario, on light colored forest soils (common in So. IL and IN, 1.5-2.5 % organic matter) and given no-till with cereal grain residue I generally shoot for around 100-110 lbs. actual N per year (this would be decreased with more fertile, high organic matter soils) with about 50 lbs. of that at sidedress. In a tilled field, you could decrease this recommendation to around 80 lbs. actual N/A per year. This difference can be attributed to a couple of factors. Tilling helps to oxidize organic matter, therefore, releasing some extra N from the soil. Also, the presence of a high carbon: nitrogen ratio residue (such as wheat or cereal rye) can temporarily tie up some nitrogen as it breaks down; this is also dependent quantity of residue present. Hence, the recommendation for slightly higher N levels to compensate under a no-till/cereal grain residue system.

My preferred nitrogen source for sidedress is calcium nitrate (15.5-0-0). It has a low risk of nitrogen loss when surface applied and I also feel the added calcium is beneficial for plant growth and good fruit development. Also, ammonium nitrate (34-0-0) is also a good option with a higher N content than calcium nitrate and low risk of N loss with surface applications; however, ammonium nitrate is becoming increasingly more difficult to find at local retailers. Urea (46-0-0) is also another option but if you are not incorporating (with tillage or water/rain) you can have very significant nitrogen loss due to volatilization especially if you do not have incorporation within 5-7 days. If you want to surface apply urea, look in to getting a product such as Agrotain® (a urease inhibitor) applied to the urea. This will stabilize the urea and significantly reduce volatilization. The down side is typically you would have purchase fertilizer in bulk rather than bagged to get this but it is an option to consider depending on what is available in your area.

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