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Soil Test Before Land Purchase

Posted Jul. 1, 2004

It is not uncommon for people to buy land without soil testing before the purchase. I realize that many things besides productivity may drive a buyer's decision for purchasing a particular parcel of land however, if more than one parcel is an option, a soil test can be worth its weight in gold in determining the better buy.

Let's say, for instance, you want to buy some pasture for grazing. One pasture has a phosphorus (P) test index of 10, which is low and not uncommon in the Foundation's service area. Another has a P test index of 50, which would require little, if any, phosphorus fertilizer in the near future. Remember, these numbers are an index of the soil's ability to supply phosphorus to a plant. How much phosphorus fertilizer will the lower-testing soil need, and, likewise, how much more could you pay for the pasture with the higher P index?

To grow bermudagrass, the lower-testing soil would require 60 lbs. of P2O5 or 130 lbs. 0-46-0 on an annual basis until fertilizer addition raised the soil test index. This can take many years.

University research and experience on the Noble Research Institute Pasture Demonstration Farm shows that soil test P can be raised by about one point for every 20 lbs. of P2O5 applied per acre. Therefore, to have equal phosphorus fertility, the index of the lower-testing soil would need to be raised by 40 points. This would require about 800 lbs. of P2O5 (20 lbs. P2O5 per index point times 40 points). That is 800 lbs. of the actual nutrient ion taken up by the plant. This equals 1,739 lbs. of 0-46-0 fertilizer or any other fertilizer containing 46 percent P2O5. At a price of $0.29 per pound of P2O5, that would be $232. So in this example, the higher-testing soil is worth $232 more per acre, based on phosphorus fertility and all other things being equal.

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