It will be interesting to hear how things are going come June, 2007.
One advantage I have is a USDA soils man at the local Experiment Station. He tells us if a soil test is to be accurate the chemicals used as an extractant must have a pH close the soil's being tested. He is adamant that any phosphate test on soil above 7 pH must be done using the Olsen (sodium bicarbonate) system. He is working on a universal chemistry but may be years from finding something that adjust to the pH of the soils.

Mehlich III produces reasonably accurate phosphate results for samples that are below a 7 pH, but is better closer to a 6 pH. The advantage for Mehlich chemistry is in it's economics, not it's accuracy. For my 8 pH soil all but Olsen are highly inaccurate for phosphate but reasonably close for K, Mg, & Ca.

I have found Bray and Mehlich tend to be low when used on my 8 pH soil. For an Olsen test a 7 ppm P is not all that bad. One test result that has the best reliability is for pH. So I can assume your 7.4 pH is good. As you know I started using a magic equation for critical and sufficient levels of K & Mg using factors derived from an old Penn State table. This was when they were still using Bray and reporting results in P₂O₅ & K₂O pounds per acre. Being basically lazy I only translated the table for my mid CEC value, 50 meq/100g. As time moved on I developed a sceptic al opinion of the accuracy of any computed CEC value. I since built a data file on measured CEC values for all my ground. On average the computed and measured are close to the same, but the computed has a wide spread on both sides of the measured.

The soil on your new rented farm and ours are much alike. We have a clay to clay loam above a soft lime base rock. On average we have 6 feet of soil but that runs from exposed lime rock to over 25 feet deep soil.

I have also observed any lab will be able to replicate the results of any sample within 10% but that separate samples pulled at the same time and locations can have 30% to 40% variation, still using the same lab. This agrees with the information I see from Oklahoma where just a few feet difference in location of a sample can produce a major difference in results. This is why the Extension people tell us to pull a large number of samples, so the soil's variations will average out. The problem is some times rather than compensating variations they are all weighted in one direction or another. It is now my practice to segregate samples so there are 3 separate samples sent in for each field. It is interesting to see the difference values. I than average the results to determine my fertility program.

Take care Don, & I hope we can visit at the AFGC conference in June.