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Colby, Kansas | In my opinion yield data is the foundation to a successful PA program, mainly because its real and it measures what were trying to manage. Everyone always says you need several years of yield data before you can do something with it,, I don't think that's necessarily true. Example, with this fall's yield data you can take your yield layer multiply that by 0.3 (for corn) and now you have a P removal layer. If you have another year or two of yield data, add those P removal layers together and you get a real good idea of the spatial variability of P removal.
As you move towards trying to establish a spatially variable yield goal (ex. for use in VRT N or seeding) several years of data will be good to have, however on uniform western KS silt loams under irrigation, I would argue you will probably need fewer years than many other locales. icgreen mentions normalization of yield data, attached is a procedure we worked on for a while. (SEE EDIT NOTE)
I agree with Marv and Mark, I have typically found that nutrient levels (especially P) are low in the high yielding areas and high in the low yielding areas.
Do you have any yield data currently available? I would use that to direct some targeted sampling into areas of high / low yield potential, and establish those points as benchmarks, so that as you implement VRT programs you can return to those sites and track your progress. If your not ready to go full throttle into this yet, I would start with something relatively simple like P and then move later into N and seeding.
In terms of software, we used to advocate the use of a program called MapCalc, it was cheap, easy to use, and we had extensive training on it here in Kansas through the KARA group. Recently I think RedHen is having some troubles as they lost some good folks, so I don't know if thats still an option. I know SMS and EasiSuites are capable of calculating VRT layers, I assume FarmWorks and maybe Apex are too (I have no experience with these).
If I can be of any further help let me know, I'm just up the road and make it to Garden occasionally.
Best Regards,
Lucas
EDIT: The attachment is too big, and it appears the KARA website is in disarray so I can't link to it either. If your interested email me and I'll email you the pdf.
Edited by LHaag 10/14/2008 22:46
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What information are people using for variable rate application of fertilizer?
