Pondering the point
Renowned soil scientist Doug Edmeades pauses to ponder the decrease in pasture production.
When I was studying chemistry at Auckland University, one of my best lecturers had an interesting phrase that he would use to emphasise an important point: he would pause and say, “it is a point to ponder.”
He used the word “ponder” not just to draw attention to something, which of course it did, but to invite us to reflect deeply on the matter at hand.
A presentation I attended recently made me ponder. It was given by an experienced and respected pasture agronomist, Dr David Chapman. His talk was entitled: “Pasture Productivity – Are we gaining?”
He was, of course, reflecting on the progress we have made over the last three to four decades in terms of increasing the productivity of our clover-based pastures.
Some perspective is essential. Clover-based pasture is the lifeblood of the NZ pastoral industry. The marginal cost of growing a kg of clover-based pasture dry matter is 4-5 cents – it is the cheapest feed source for ruminants.
Furthermore, the clover component – it fixes nitrogen (N) from the air – adds about $1.7b of N to the pastoral economy. All up, exports from the pastoral sector are worth $35b annually. For all these reasons, the question Chapman poses is of vital importance to the national economy.
His opening gambit was data from the dairy industry, showing that from 1990-91 to 2004-05, pasture eaten increased at a rate of about 1.75% a year. Since then, the rate of increase has effectively stagnated at about 0.25% annually. There is no directly comparable data for the dry stock sector but other data Chapman presented showed a decreasing trend in pasture production in this sector also.
The relevance of these trends is worrisome because we know, at least for the dairy sector, that operating profits are directly related to the amount of pasture eaten. Is it possible that our pastoral sector has stalled or is stalling?
Putting the dilemma differently, the productivity of our pastures – the ratio of inputs to outputs – has shifted, eroding the much-vaunted international competitive advantage of our pastoral sector.
Chapman dissected the forage industry looking for the possible factors which could explain the trends in pasture productivity over the past three to four decades.
While accepting that there has been some progress at the plant selection and breeding level, he suggested these trends were not being captured in farm-system research or indeed on the farm.
His conclusion amazed me: he suggested that “N fertiliser has been the only clear and obvious source of pasture productivity gain at the national level.” Certainly, a point to ponder?
But there is an elephant in this room. If Chapman is right, then the question that follows is; what has the industry been doing?
We are told that, as a consequence of science reforms, beginning in the 1990s, little public-good research is now being undertaken by the Crown, i.e. in the CRIS.
What research there is, is being undertaken by the private sector, i.e. the seed industry. Being commercial entities, they naturally focus on their market share rather than public-good research and at the centre of their marketing is the Forage Variety Index (FVI), which ranks ryegrass cultivars in terms of their performance.
This focus on ryegrass has always intrigued me. Surely if clover is the most important component in our clover-based system, why is there no ranking of clover cultivars, preferably grown in conjunction with ryegrass cultivars?
I think the pastoral sector has lost its focus. Day after day I see the consequences of this on the farm. When I was a young scientist, in the 1970s, we did a lot of fertiliser field trials and I can recall that farmers loved to look at various fertiliser plots.
I like to think they left the trial site with a clear mental picture of what a good, well- fertilised, clover-based pasture looks like. But we don’t do such trials any more and as a consequence, we have a new generation of farmers who do not know what a good clover-based pasture looks like.
If they are lucky, they may be advised that their pastures have ‘run out’ and they need to cultivate and resow with the latest ryegrass cultivar. And they wonder why, after a few years, they are back where they began.
You see, therein lies the rub. Clover has a higher requirement for all nutrients.
The fertiliser policy should be directed at growing clover. Because without the proper nutrition clover will not flourish, the soil nitrogen level will decline and because of this the ryegrass will not persist. The solution most farmers are told is to use more fertiliser N.
Hence Chapman's conclusion. The major driver of pasture productivity over the last 30 to 40 years has been nitrogen fertiliser use.■