What’s Your Olsen P? This is commonly the only question asked, and answered when discussions, among farmers, on soil fertility take place.
Do you really understand what this means?
Are you willing to spend another $200 to $500 a hectare a year on applying P that you may not need, that you won’t use, and that will probably add to environmental runoff that you may be taxed for!
Here’s some basics about your “P levels”.
Back in the days, the most accurate soil test for measuring available Phosphate was a Silver Nitrate Test.
Silver Nitrate is expensive and it took more than twenty four hours to get an accurate extraction. But it was accurate.
The Olsen P test was created for alkaline soils [soils with a pH greater than 7]. We have very few alkaline soils in New Zealand (minute amounts)!
The Olsen test was very quick (only a couple of hours). Baking soda is the active extraction method.
On a Dairy Farm doing 1000 kg hectare of Milk solids there is approximately 7 kg of Phosphate per hectare removed from the farm in Milk each year [Dairynz figures]. The P in supplements brought onto the farm and the P in rain water largely replace the P exported in milk so there is very little actually lost..
Now if you are not accurately monitoring your phosphate levels by using appropriate extraction methods and also testing for the total amounts and available amounts of Phosphate before you purchase your fertiliser YOU WILL BE WASTING MONEY!
And you will be wide open to compliance issues regarding phosphorus runoff.
If you are comprehensively testing and have accurate figures and apply fertiliser only if it is actually required compliance issues will be mitigated.
What we really need to look at is limiting factors. We need to attend to all the required nutrients as well as the biology and the physics of your soil to get it into a more productive state.
The easy way to get around all of the unnecessary costs and the environmental and compliance issues is to get yourself educated and you will save time and money.
For a free consultation Call Ewan not on the P Campbell.