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Deer Park, WI

Switching gears to a slightly less controversial topic...

Curious to gather input on what growers believe seasonal nitrogen use is and how to meter that input across the season.

N is a challenging nutrient, so important yet so elusive. As most know, it moves rapidly through the soil profile, unlike its relatively stationary peers, phosphorous and potassium.

The "pumpkin production guide", produced by NRAES, suggests nitrogen is the most limiting nutrient in successful production and that a field crop requires roughly 120lbs/acre/season. For reference, many grain farmers recognize that it takes roughly a pound of N for every bushel of corn produced per acre. Thus, 200bu/acre corn roughly needs 200lbs of N in the soil throughout the season. It is probably safe to assume that success in the competitive patch requires between 120-200lbs of N.

Coming up with a ballpark figure for the competitive patch may be helpful to establish meaningful guidelines such that we do not over or under apply this vital nutrient throughout the season.

Conventional agronomy practices will credit soil ~30lbs of N for each % of organic matter. If your soil test shows OM of 5%, it can be assumed that you have roughly 150lbs of N in your soil. The caveat here, of course, is that this N is in an organic for and likely not readily available for plant nutrition early season, before the microbes have converted it to the plant-usable form of nitrate (NO3) or ammonia (NH3).

Part of the challenge here is doing the math on what you are applying and over what size. The first number in the fertilizer triad tells you what percentage of the product is Nitrogen, but says nothing about how much is actually applied per acre or square foot.

Has anyone crunched the numbers to develop an N-rate for giant pumpkins??? Would love to hear your thoughts.

4/28/2015 1:08:54 PM

Austin MN

Joe shoot me an email I have a product I came up with that I tested at school for early and late session nitrogen :)

4/28/2015 1:59:00 PM

JACKSON, WISCONSIN. ; )

joe lots of people crunching numbers.... I have not done the math however I think with rough numbers... Approx 20 pounds or so. Of Nitrogen for 6 to 8 plant sites. I only spoon feed it when I see an issue. One handful at a time. I use a turf grass fertilizer.

4/29/2015 9:06:41 AM

Colorado

The plant prob. pulls in the majority of nitrogen in the first half of season which further complicates when and how much.

4/29/2015 2:08:07 PM

Glosta

Just to use as a reference, on western labs site presentation from the 2010 GPC seminar shows Dave stelts test from when he grew the 1662.5 , his nitrate level was 100 ppm (200lbs per acre) and they still recommended him to add 1.4 lbs of N per 100 square feet or (~60 lbs per acre) more. so thats 260 lbs of N per acre.

His ammonium was at 8ppm. Western doesn't measure the OM% by LOI (los of ignition) they measure the actual humus content i believe. not sure if that correlates to the 5% om rule the same. But I'm sure he had plenty of OM to convert to N given they rated it a medium OM% on his test.

Plants readily take up the nitrate form but need Molybdenum to convert it to the used form of ammonium, they need Molybdenum in order to convert the NO3. SO is it the amount of N we supply or the type that is important. it seems Mr stelts had plenty NO3 and very little NH4 on his test, did the OM make up the difference or did his PH of 7.3 make enuff molybdenum avalable to convert all that NO3?

4/29/2015 5:51:57 PM

Willamette Valley, Oregon

This is a handy brief reference about nitrogen:

http://www.spectrumanalytic.com/support/library/ff/N_basics.htm

The first table shows how much N typical agronomic crops might pull in a year (far right column is the total used by plant and fruit). Pumpkins aren't on there specifically, but I'd guess it's in the high end of that general ballpark.

Doesn't mean you'd add that much, because some will be in the soil already, but you'd want to make sure that much was available, without over doing it.

4/30/2015 7:37:28 PM