Reading through the recent volumes of articles relating to pasture persistence, perennial ryegrass cultivars and the various endophytes, one wonders if somewhere down the line we have lost the plot? 

History has a way of repeating itself, certainly it seems to be in Hawke's Bay and there are rumblings of the same issues in Canterbury.

Back in the late 1960s and 70s there was a marked departure from pastoral farming as farmers chased the golden wheat and other cereals. At its peak in 1968-69 some 4000ha of wheat were grown through Hawke's Bay.

As cereals became vogue the plough hit a lot of permanent pasture and for many years we had grain following grain or 4-5 year rotations involving cereals, brassicas and 3-4 years of pasture that didn't persist too well.

The years in pasture were usually dictated by grass grubs of the day living in a disease free world. Or was it that frequently established pastures and the pressure on us to get back to wheat saw the demise of soil structure and the soil's ability to support new grass for much more than a few years?

Wheat fell out of favour, lamb prices lifted and there was a major swing back to pasture. Some 10-15 years had elapsed and suddenly pastures were expected to be as persistent as those of yesteryear.

No such luck! Firstly, a good deal of the old permanent ryegrass staggers (RGS) type pasture had succumbed to the plough and secondly DDT, a good deterrent for insects, was now banned. Thirdly, unknown to farmers and scientists, the new and not so new cultivars (less turnover of seed probably meant longer seed storage periods) on the market were largely void of the unknown endophyte.

There were only about 5-8 cultivars to choose from in those days; Ariki, Ruanui, Nui, Ellet and perhaps Hawke's Bay PP or was it from Marlborough or Canterbury. Endophyte in some grasses was known about since the 1940s but never in the context of causing ryegrass staggers or protecting plants from the vagaries of Argentine stem weevil (ASW).

So new pastures were not persisting and pasture was at a premium for millions of sheep. Why were the new pastures not persisting? The importance of research and lateral thinking in the 1970s and 80s has certainly contributed to today's management of pasture.

In the late 1970s at Takapau Research Station in Hawke's Bay scientists and staff successfully searched for a ‘green' option to control grass grub.

Clovers and ryegrass were selected that seemed to be a little more tolerant of grass grub. The sowing of these selections in a trial designed to measure their tolerance to grass grub revealed immediately that the first problem was not the grub but ASW. They had a heyday on Ruanui and Nui but left Takapau standing out like an oasis. The reason had us scratching our heads for a while.

This was a first for New Zealand. Following up, some pretty sleek work saw ASW actually choosing perennial ryegrass tolerant selections in the laboratory overnight using a ‘preference test' technique. It identified a range of ASW tolerant lines and some old persistent pastures and surprisingly, some persistent plants in supposedly susceptible ‘new' cultivars.

Basically these ecotype escapes had developed over time. At the time it seemed sensible to save the seed from them and sow it. It worked for persistence; seed lines of Manatuki, Ratanui and TFRS Droughtmaster ring a bell. That was vogue for a while as the industry caught on and so did RGS, unfortunately.

The association of ryegrass staggers and endophyte was discovered. Then almost two years later the discovery that peramine, an alkaloid associated with endophyte, was the culprit conferring tolerance of ryegrass to ASW. What a breakthrough given the worries of poor pasture persistence. Another clever success story was the dampening effect on ASW by the parasite Microtonus aethiopoides along with prudent management strategies.

That was the catch 22 of the time. Either aim for persistence and put up with RGS and its consequences or use ‘nil' endophyte and have no grass to feed.

The farmers as consumers asked the scientists if it was possible to bridge that hurdle and AR1 was delivered.

It was a logical step to chase an RGS free/ASW tolerant ryegrass; it was ingenious and cleverly won NZ research that has gained us international recognition in endophyte research. Some of the endophytes have not been so good and we don't hear much about them for a good reason.

Now the consumers seem to be unhappy with the goods.

But wait, AR37 has to be incredibly innovative. Maybe there is a trend to some staggers but it provides protection from black beetle and porina caterpillar and perhaps two newer ones (root aphid and mealybug) responsible for the reduced persistence of AR1 pastures in Hawke's Bay during the 2007 January-June drought.

So we are seeing 30kg less MS/cow/year and some staggers with AR37. I am not a dairy man but this sounds like about a 4% loss in production (on the basis of 750kg MS/ha, is that realistic?) and I would humbly ask is this not a sound trade off for extended pasture life and relief from re-sowing costly pasture? The benefits of some freedom from porina caterpillar and root aphid have probably yet to surface. That must be worth a lot in affected dairy regions such as Tararua.

Should we also remind ourselves that 25 years ago in well run trials we were seeing lambs grazing high endophyte ryegrass, stressed by RGS loosing 10g/day during the summer months, not to mention stock welfare. The affect on cattle, the general stock losses due to dehydration and death by misadventure as they helplessly fell over cliffs or drowned in dams. Then there was the ‘dags' issue, untidy back ends, poor stock thrift and elevated body temperatures due to ergovaline.

Compare this with healthy happy lambs gaining 100g/day in the same summer period on the same grass less its endophyte (in our trials the same seed lines were used but zero endophyte was obtained by treating the seed with fungicide to take out the endophyte).

But most importantly, that same grass genetics with zero endophyte described above had disappeared within 1.5 years at the mercy of ASW attack in romped the thistles and the grass grub never got a chance!

I like to think we have moved well away from wild endophyte and all its worries, especially in warmer, drier environments where it hurts most do we really need to revisit that era?

I believe today's concerns are more about the 40 odd cultivars on offer today and each one is almost the best it seems. At the end of the 2007 drought, On-Farm Research, Poukawa, published results showing different perennial ryegrass cover/persistence scores for a range of AR1 inoculated cultivars all managed under the same grazing and mowing technique. Now, were some outstanding differences due to AR1 failure, cultivar failure, insect pressure or a combination of all three?

My experience tells me that pasture persistence is about using the best genetics for a particular environment and stock class. Include in this selection process local pasture pest pressures and of course good soil management.

It may be prudent to ask if AR1 has outlived its usefulness in drier environments?

I'll wager the recent build up of root aphid may be the consequence of farming along for a substantial period with AR1, encouraging the population to increase beyond the damage threshold and hence the crash in persistence. It happened in a similar way with ASW under ‘nil' endophyte with no parasite back in the 1980's.

It's obvious stuff. In a sense we are struggling against nature and nature will never let us win. We have to place new technology ahead of it. If the pasture is not the best for the environment and our management isn't up to it, it will fail with time. Select that endophyte and pasture cultivar carefully!

When it was vogue to sow short-term pastures annually or bi annually I have observed mighty poor root development. Just as a few roots were getting down out comes the glyphosate to make way for the new. The soils in such systems lack organic matter and structure. They become platy, pugging is a major issue and worms are lacking.

Persistent pasture could be defined as that which survives for more than eight years. Here the natural species of the farm develop amongst the imposed species. The proven species for the environment chip in around year six filling the gaps left by less persistent pasture. Management becomes king to maintain as productive pasture as possible. Organic matter levels increase, fertility increases in the top 5cms where it matters and improved worm populations shift the below groundmass around keeping soil healthy.

Do we really give the soil a chance? Is it not time to question the total sustainability of current management systems? As fertiliser and other costs soar we may need to analyse carefully what we are ‘actually doing'.

Can we realistically get a sustainable return on repeatedly sowing new pasture? It comes down to wise decisions, getting it right and as always with farming, some good luck.

Thank god for science. Yes, there is always a need to sow new grass and I will never refute that. Importantly scientific advances are critical to sustainability of farm systems and management. In the context of AR37, I believe we can only benefit from injecting it into our pasture system. Mother nature hasn't dismissed ‘wild endophyte' given the endophytes ability to withstand insect pressure and I think AR37 will be a better bet here than AR1.

Grasses inoculated with AR1 are susceptible to root aphids so the grass will have less chance of surviving in the pasture matrix.

AR37 appears to have all the attributes to withstand a wide range of pests. As an independent I suggest AR37 is a timely addition, it should bridge the gap between ‘wild' endophyte and AR1 in terms of animal production and welfare and pasture persistence.

Consumers, lets be careful we don't toss the baby out with the bathwater.

And remember, the right cultivar, endophyte, good soil management and pasture-grazing management equal persistence.

Mike Slay is an independent pasture consultant and former AgResearch scientist.
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