Barry, if I were you in your specific area I would assign yields to your zones based on plant-available-water-holding capacity. My range would be from 80-140 on corn, but it could be whatever you think is realistic. The really poor areas you will want to assign a really low yield to so that you cut back on expenses on them.
For now I would divide my yield goal for a specific spot by 8 and take the resulting figure times 1,000 to arrive at a corn seeding rate. If it was looking dry going into planting I would change that by dividing THE SAME YIELD GOAL by 10 before multiplying times 1,000.
This is not the same as adjusting your yield goal if it's dry. The reason is that you are not truly limiting the yield goal you originally had. You are simply making that yield goal a little bit harder to achieve because your ears will need to be slightly bigger due to lower plant pops. By getting focusing on defense you leave some offense on the table but you can still achieve those yields if Mother Nature turns around and cooperates.
Very few people plant at 8 bushels per thousand in your neighborhood. They usually plant maybe 4 bushels per thousand and the result in my opinion is lower yields. In time people will figure this out, but it will take some experimentation.
In your opinion how valuable are this last years yield maps...I have heard they can really define the water holding capacity and show some sharp soil variations...I have one 80 that I am thinking of VR planting based only on last years map...
For me, my last years maps are going to be the most valuable maps I have. This year might suck but I now know exactly where I have the prime soil. I went from 240 to 0 in a pass so it is a good tool to put into the bag.
Do you think a guy could create some management zones that could be a baseline for even above avg. moisture yrs...
By using last year's maps? Yes I do. Even in last year's drought the low-lying poor-drained soils where among the lowest yields due to salt content.
The name of the game with VRT is to NOT throw inputs at junk soils. You can't turn a sow's ear into a silk purse. Push the good ground (in Brule County that's the hillsides) hard and don't expect much from the rest.
I have never worried about VRT with 10-34. We use 5 gallons an acre so I don't really worry about it. I only want the 10-34 to give the corn plant the boost it usally needs when it is cold around here.
I have heard that as well...do you sidedress...thats another area that I have VRT capability...we bought a new sidedress rig that has varible rate pump on it...thinking of doing VRT there as well with 28%...
Yes I do sidedress. I spread urea over the top. I have in the past used a 28% rig to do it, but lately I spread urea over the top when it looks like it's going to rain. The urea with a spreader had been used to the south of me for YEARS, they have never lost a crop yet, nor have I. I like the urea over the top because I can cover acres fast.