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| This has been something we have been thinking about in earnest since we started variable rating seed in 2009. Here is our opinions on your ideas.
#1 As stated before, there is a problem using yield maps because some years low areas are bad and some years they are good. The same for higher/ sandy areas. SO for us that kinda shoots that one down.
#2 Again same as before, the soil types would help some, but yearly rainfall to us is the big snafu with that.
#3 A great idea, buy how does one accurately decide what ground can produce how much given a certain year.
It really sucks because we would love to variable rate N. What we have heard/learned: People that use things like Greenseeker most times wind up putting the heaver rate of n on the poorer soils and less on the good ground. Contrary to logic. It's crazy. They say overall N use is about the same. We have also thought about post season tissue testing so see if the plant was short on N. That would give us some basis for that year under those conditions, the plant had/did not have enough N. That might help build a map the next year to go off of.
We have also heard of doing soil samples right before side dressing. That is time consuming, and unless done right before the rig comes to the field, it can be skewed by any rainfall near sidedress time.
There are people that tissue test near side dress time, again can be skewed by soil and rainfall conditions.
We have heard of using Greenseeker and the like also, but the problem there is you have to have check strips in every field of both high and low N rates, and have to do this for every variety in that field, and THEN calibrate for every variety and field also.
What we are thinking at this point is some sort of NDVI map, just like what a Greenseeker does, but either by airplane or now there are even guys doing it with remote controlled small planes/helicopters.
There are also NDVI maps done by satellite, but they say the resolution with them is not as good (of course the airplane guys tell us this)
What's the best way? I'd have to say all of them. In a perfect world, I would use soil types, previous harvests, the seeding rate, the current weather, tissue sampling, soil sampling and NDVI mapping. Maybe THEN I could variable rate N. If I could get done with all the sampling and afford to pay the lab.
I think this year we are going to try some of the aerial NDVI to see what we can learn from them and combine them with all of our known data (seeding rate, soil types, wetness of the year).
I'm lost | |
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Variable Rate Nitrogen (sidedress) discussion
