Calcium and diseases

Better soils
with Brett Petersen
Kiwi Fertiliser & Golden Bay Dolomite

Research on calcium is rare. It’s the opposite for lime, but focussing on one nutrient will never allow the truth about soil fertility to be found. Calcium depresses magnesium in the soil and this needs to be factored into the benefits for liming. One NZ paper by N. Thomson noticed magnesium increased in the soil but cows still suffered hypomagnesaemia after applications of lime. The supposition offered was that increased calcium caused a decrease in magnesium uptake by the pasture.

The message is clear. Treat calcium and magnesium in tandem. We work out magnesium requirements before calcium to get the right answers. The pH is the result of the fertiliser programme, not the cause of it. Trying to construct pH does not help. When correct soil balancing takes place, pH will also be correct. We’ll look at properties in common ownership; the difference being one had Mycoplasma bovis while the other did not. M.bovis is one disease. Facial eczema is another. There are many more. The list includes insect pests. If you follow nature’s rules, these man-induced diseases will not occur on your farm.

Farm A

Farm A has an average pH of 5.6. Desired calcium is 4278kg/ha (68 per cent Base Saturation), but the actual readings are 3361 (53.6 per cent BS) being 917kg/ha of elemental calcium short of requirement.

Magnesium needed for 12 per cent is 453kg/ha and the farm has 389kg, or 10.3 per cent. Potassium is not well represented. The herd from the farm was slaughtered as the cows were severely affected by M.bovis. The remedy for this farm is 1500kg/ha of Dolomite and 3500kg/ha of high-quality lime.

Farm B

Farm B has an average pH of 6.6. Calcium is 3291kg/ha (69.2 per cent) when 3232 is required for 68 per cent BS. Magnesium is overdone with 434kg /ha (15.37 per cent) when 342 is required for 12 per cent BS. Potassium is well represented. All three cations contribute to pH. (If pH 6.3 was desired, we are 0.3 above that; magnesium makes up 2.28 of the extra 0.3 pH; calcium only makes up 0.02.)

This property is still susceptible to hypomagnesaemia so 900kg/ha of lime can be added (pH will decrease in this case) to allow magnesium to become plant available or let the Mg drift back over time; a riskier strategy. Some cows had been purchased from a M.bovis-infected property. Exhaustive testing during three months occurred on Farm B. No infected cows or M.bovis were found; no anti-bodies were found; no M.bovis -related diseases were found but the Ministry for Primary Industries destroyed the cows regardless.


M.bovis was first isolated in 1961 from USA feedlots – industrial-type enterprises. By 2012 it had reached Argentina, following feedlots which began around the 1990s. Apparently, M.bovis is naturally occurring in the upper respiratory tract, and can be shed via nasal discharges. It is also in the genital tract of male and female healthy animals and can be spread by intercourse and by frozen semen. Milk can also be infected and can be a source of calf infection. Other animals known to have M.bovis are sheep, goats, rabbits, poultry and farmed Bison where feedlot herds are 17 times more affected than Bison cow-calf operations. M.bovis can also be isolated from humans.

Acknowledgements: David Law, Forward Farming. Carlos A. Margineda Sonali Saha A Kumar


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