with Brett Petersen
Kiwi Fertiliser & Golden Bay Dolomite
Over the years, Kiwi Fertiliser has encountered many cases of paddocks fertilised with whey from the dairy factories causing problems for soils, plants, and animals.
Growth rates have been around 25 per cent less than non-whey paddocks. That also means the health of the pastures is not optimal, weeds such as yellow creeping cress, have invaded, and milk fever has killed some cows that do not respond to conventional treatment.
Problems and solutions
It is unsafe to use these paddocks for springers, or colostrum cows. One of the issues is excess potassium. Of course, milk fever is a magnesium problem. One farm we know supplemented magnesium and calcium at double doses for an entire season, to keep the cows from dying.
So, what are the problems and how do we fix them? The problem can only be solved by taking a soil audit that can be accurately interpreted and balancing the soil with the correct amount of required minerals.
By using the Perry Agricultural Laboratory tests and combined with manuals produced by Kinsey Agricultural Services, we can solve all problems caused. It appears that other soil test results cannot be interpreted accurately enough to effect a solution. The main problem is the interpretation of pH.
pH is the measurement of hydrogen ions. It is not an individual measurement of calcium, magnesium, potassium, or sodium levels.
All about the levels
Potassium can raise pH in the soil. (So too can Ca, Mg, and Na.) A ‘high’ pH can and often does cause consultants (including Fonterra personnel) to advise against applications of lime. Again, the thinking is not correct. The pH is NOT the problem, but how it is constructed IS the problem.
Calcium is to blame for the high pH, so calcium cannot fix it!
Wrong! The interpretation of the soil tests the consultants look at is not accurate enough for them to arrive at the correct analysis and solutions.
So let us look at an example that causes the problems above.
Looking at the graph on the Hill test, Ca, Mg and K are all in excess. According to this interpretation, adding Ca will not help solve the problem.
Interpreting the PAL soil audit, Ca is low, (less than 60 per cent,) Mg excellent, K
and Na are excessive. So, the solution is to add Ca.
But how much? We need to consult the KAS manual and calculate how much Ca
is required to raise Ca, and reduce K, and Na. The answer is lime at 3.4t/ha will serve that purpose.
These calculations include the TEC of the soil, so are specific to the soil covered by the soil test. In this regard, no one should look over the fence and copy what someone else has done. They need to test their own paddocks to get the correct information for their problems.
But, what else do we find out? Simply that when K in the soil is greater than Mg, Mg is blocked by K, hence the “incurable” milk fever in the cows. Just take this a step further. The pastures, animals, and the effluent pond will all reflect the health (or ill-health) of the soil.