| mocorn - 12/5/2012 09:26 Isn't this thread really interesting? We have people telling us to grid sample or zone sample or sample based on yield maps and then variable rate spread fertilizer based on those soil test results. But then here a guy has results that some don't want to accept so we backpedal and say check another sample or did the lab use the right procedures or maybe its goofed up because of the warm winter. And comments like well a soil sample is just a snap shot of one location at one time......... I don't mean to sound too negative but these are some of the reasons why I can't quite buy into the whole variable rate concept yet. Our fields are mostly pretty consistent and we have always been very picky about even spread patterns of all spreading devices : lime trucks, litter carts, dry spreaders, strip till dry box, NH3 bar etc. I'd hate to think of all the time I've used spread pattern pans. Anyway after all I do to try to maintain consistency I guess I just don't trust my soil sampling and the test labs quite enough . And when it's all said and done a lot of years it comes down to how well I irrigated. Thanks The important difference here is trying to compare across years, versus everything sampled at once (grids) to estimate spatial variation. The original post says the same company did the sampling, but was it the same person? And exactly to the same depth? And were the spots GPS'd the first time and returned to the second time? How many cores per sample? And how many total samples are we talking about, both from the earlier set and from the recent set? And, check that the lab's OM procedure is the same, as Steve G and others have mentioned. The other people who've posted give good reasons why OM may have truly declined. More soybeans in rotation, drain tile installation, removal of crop biomass, etc. |
Organic Matter Going Down In No-Till
