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Victoria, Australia | What sort of acres are you guys talking about gridding 2.5 acre samples on? I set up our farm last year based on the three soil groups we have, and zoned them with the spatial data I had (with a bit of scouting as well) and basically designated two testing points/soil type/field (10 cores per testing point to create and avg) so I end up with three samples/field and went from there. At $40 bucks a test over here just the soil test costs alone for grid sampling would near net out the benefit of VRT not to mention the confusion created! No doubt my method will need fine tunning over the next couple of years, but even this year (our first VR year) our NDVI images have came back more even than ever, whilst saving around 30% of our N + K bill.
Simply saving point shp. files on your tractors gps gives you an accurate means of coming back to the same location for tissue sampling and future soil samples, that makes life easier. This in my opinion is the most important aspect of the whole process. Without repeatability ( within a metre) in your testing locations you can't be sure on the impact you are having on your soil. Years of random testing by various agronomists, led us to beleive that our soil pH was around 6.5 and that our OC was 2.5% (not to mention N,P,K) only to find through accurate sampling (years later) that our pH was actually 5 and our OC was only 1.8% which meant we missed out on 5 yrs of lime applications which cost us $$$ and that our 10yrs of no-till had only raised our OC by 0.5% rather than the 1.2% we had been excited about.
For us it's about knowing each major soil types weakness, and basically create production zones, so we get the most out of the good stuff and don't over do it on the poor stuff.
By the way, I wasn't knocking the 2.5 acre grids, just curious on how you could justify it over a few thousand acres.
Just my 2 bobs worth, Cheers
Jim | |
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Grid sampling and tissue testing.
