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gpsdude

Posted 12/19/2025 11:02 (#11476408 - in reply to #11467304)
Subject: RE: Prescription map steps between zones

NE South Dakota Clark, SD

I will be the odd man out here. Does your yield data have hard breaks in it at a line? Do your soils have hard breaks where they change? The only time I have seen either is because of a man made event. Not all software systems make zones the same way. Most variable rate software systems create zones that have 1 value for the entire zone so you end up with hard break lines in your fertilizer and seeding maps. A floater running 18 mph spreading fertilizer takes quite a while to change rate by 50 or 100 pounds. So this means over fertilizing when going into a lower production zone and under fertilizing when going into a higher production zone. If you ever look at the application maps you will see this. The pounds applied for the field will be pretty close as they will average out across the field. If you are happy with semi precision ag this works. If you are looking for site specific precision ag there are better ways. Planters and air seeders do a better job changing rate because they are going much slower. In the pictures below the first one shows what a typical zone map looks like. In the second picture it is the same map showing what interpolation looks like. Most software systems do not do this. Which one looks more like your yield data? In the product prescription maps below the rates will step up and down in 1-3 pound increments which makes it very easy for the machine to keep on rate. Unfortunately these maps will have to be dumbed down some to work in most controllers as they have polygon limits.

The next map shows corn yield goal 160-235 bu/ac, 24 inch N soil test 45-96 lbs/ac, Organic matter 4.6-5% followed by 46-0-0, AMS, phos soil test-Olsen 16-30 ppm, 11-52-0 0-118 lb/ac and lastly total N available from soil test, OM, AMS, Urea and MAP.

Edited by gpsdude 12/19/2025 11:04