When I started working with farmers 40 years ago, if you asked a farmer what fertilizer he used, he would invariably tell you how much Super he was applying. Back then fertilizer was either straight super or potassic super. Most farmers could readily rattle off the units of P being applied per acre. It was common to see soil ‘Olsen P’ levels in excess of 60 on loam soils and as high as 110 on some pumice soils. Pasture commonly came back at levels in excess of 0.55% P on a dry matter basis.

At the time, if you had the courage to suggest to a farmer that he consider cutting back the phosphorus he used… he would give you a very nervous look.

Jump forward to the present day, farmers haven’t just been weaned off their P addiction, many have gone cold turkey. Because of environmental constraints around feed brought onto the farm, many farms see little or no P fertilizer being applied. As the fertilizer budget is reduced, this situation has seriously decreased plant P levels. Adding to the issue is that NZ cows used to be fed mainly grass. They are now fed a variety of feeds, many being P deficient yet supplying high soluble sugar or starch level. Where it used to be rare to see a case of phosphorus deficiency it is now becoming a common problem.

A DEVELOPING CONCERN
There is hardly a day goes by when we don’t hear from a farmer describing what they think are normal calcium deficient downer cows. When questioned, the symptoms often don’t quite fit, these cows don’t always respond so well to normal treatment. Sometimes a bottle of calcium in the vein will get them up, only for many to go back down again later. Often these cows will only respond to a calcium phosphorus combination into the vein, or if given calcium borogluconate can tend to go down again.