Six months later in the autumn-winter period, when pasture damage usually shows up, the compacted area was relatively free of grub damage.
So Jeff decided to try wintering some of his R1 Friesian bulls on this grub-prone area, using a Techno system, to try and replicate the compaction effect.
There are heavier soils on the Dickins' farm but most are high phosphate-fixing loams of volcanic origin.
The Olsen P levels on the farm are low because for many years they have been using reactive phosphate rock (RPR) as the source of phosphate. However, the Olsen P test only picks up the soluble phosphate in the soil and not the insoluble phosphate that has yet to be released from the RPR.
Another phosphate test, the Resin P test, would give much higher phosphate readings on Jeff’s soils because it tests for both forms of phosphate.
Jeff has been using combinations of soluble phosphate and RPR at annual rates of 25 units on the hills and 35 units on the area occupied by the techno system. Recently, he applied a capital dressing of lime to lift available calcium levels and also applied some DAP to provide more soluble phosphate.
“I’ve dabbled in some other products that were supposed to improve soil health. However, I could see no advantages.”
With summer droughts reducing pasture covers to very low levels, Jeff won’t hesitate to apply nitrogen in autumn to build a feedbank for winter.
The Dickens’ usually apply 25-30 units of nitrogen over the whole farm in autumn, and also use it strategically in spring if a feed shortage is anticipated.
Jeff also addresses the grass grub problem by under-sowing badly damaged areas with cheap grasses. He says modern grasses just don’t stand up to bad infestations of grubs.
Finishing feed
No cropping is undertaken on Jeff Dickins’ Apiti farm. However, there are seven hectares of plantain covering four paddocks, providing quality finishing feed.
“The four paddocks enable me to rotate stock over the area, giving me the opportunity to get the most out of the plantain by not overgrazing,” Jeff says.
They used to grow chicory but its winter growth was poor, compared with plantain, which grows as much as grass over the same period. While there are some management issues with plantain it is much easier to manage than chicory although the grubs do seem to like it.
Caution urged
Sandra Taylor
Soil scientist Doug Edmeades is warning farmers against using the Resin P test as an alternative to an Olsen P soil test.
Writing in agKnowledge’s Fertiliser Review, Edmeades said if consultants insisted on using it, farmers should remember that if the optimal Olsen P for near maximum production was in the range of 30-40, then the equivalent Resin test should be 60-70.
He said there was a direct relationship between both tests in that when the Olsen P went up or down, so too did the Resin P level. This indicated that the two tests measured the same pool of available soil phosphate, albeit extracting different amounts.
The Resin P test was introduced in the mid-1990s. Edmeades believed it should never have been released because it was only properly calibrated on four sites in this country.
He said the test wasn’t able to estimate the particle size of the RPR residues remaining in the soil, which Edmeades contended was the most important factor determining the plant availability of the phosphate in RPRs.
