Opinion

Are we managing our grassland correctly?

By John McHugh, dairy farmer, Portlaoise, Co. Laois

The importance of grassland to the Irish livestock farmer is well recognised, enabling us to maintain a competitive cost of production.

In recent years, interest in achieving more from our grassland has increased – with lots of farmers now completing weekly grass budgets and contemplating ambitious targets of 16t or 18t DM/ha (dry matter per hectare).

However, have we have strayed off course in our approach to grassland management? By targeting 16t or 18t DM/ha are we just falling into the same old output trap, replacing the 10,000L cow with 18t DM/ha?

The maxims of the current Irish approach are maintaining grazing residuals of 3-4cm and maximising grass utilisation which, in turn, keep the grass constantly in a young leafy, quality state – hence maximising animal output. But is this approach short-sighted?

Constantly grazing to very low residuals and maximising utilisation now means that very little grass (carbon) gets returned to the soil. Moreover, what does get returned is leafy, soiled grass that gets broken down by bacteria and released back to the atmosphere very quickly.

The result is our soils become more compacted and anaerobic; that can only be measured over the medium to longer term.

Hitting very low residuals every 21 days also means our grass roots have very little scope to penetrate deeply into our soils. All of this leads to a degenerative system of grazing, that will become more dependent on imported fertiliser to maintain yields.

The clover plant often fills the niche of restoring these run-down soils in nature by, firstly, providing a suitable environment for the nitrogen-fixing bacteria in its root nodules and, secondly, supplying the calcium and other minerals required for this process.

However, there are more than 1,000 different free living microbes that can fix nitrogen in our soils – if they become healthy and aerobic with a diversity of plant life to feed them. Nitrogen deficiency is a man-made problem and its real solution will be found in appropriate management – not in a bag of chemicals.

The current wisdom also strives to constantly prevent our grass from going to stem and seed and the subsequent quality and production loss that accompanies this. But, once again, is there a catch?

Silica is the second most abundant mineral on the earth’s surface; yet its abundance in our food has dramatically declined over the last century. It plays a critical role in human, animal and crop resistance to disease and pests – an issue that is becoming increasingly critical as antibiotic, fungicide and pesticide resistance become more widespread.

Again, chemical applications to soil, along with constant suppressing of the stem-forming stage of our grass, seem to suppress the microbes that solubilise the abundant silica in our soils into plant-available silicic acid. I could speculate that this is one of the reasons that organic farmers claim an improvement in their animals’ health.

Mob-grazing utilises these principles, along with those I mentioned in a previous article on Dr. Christine Jones’ work.

Also Read: Building soil fertility in a sustainable way

The return of organic matter to the surface of the soil eventually breaks down and gets distributed through the soil, creating aerobic friable soil conditions where nitrogen fixation can occur. This nitrogen can then combine with the liquid carbon release from the various plant roots to form humus.

The current approach to grazing is embodied by the Greenfield Dairy farm in Kilkenny. It exhibits a soil run-down after years of tillage, where grass growth will remain increasingly dependent on chemical fertilizer – and limited by increasing fertilizer regulations if this system continues.

grass soil humus nitrogen grassland
Image source: Shane Casey

The old adage – something that seems too good to be true usually is – is becoming more apparent in the chemical ‘quick fix’ solution that is artificial N, P and K. It needs to be replaced with management practices that are in sync with the workings of the natural world.

Money spent on N, P and K in its current form is not an investment, but an ever-increasing black hole. It needs to be replaced with real investment in our soils, which starts by returning a little more carbon. With time and patience we can utilise the power of compound growth in a much more positive way than ever before.

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