Teagasc would have us salt the earth

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

Many farmers have and continue to invest heavily in building the phosphorous (P) and potassium (K) in their soils to the recommended index 3 or greater, as measured on soluble soil tests.

Farmers are already frustrated with the limits on P applications, making it difficult to maintain optimum levels. A major question hangs over this whole approach.

Phosphorous run-off from these high-index soils is recognised as one of the causes of eutrophication – a spike in nutrient levels in our waterways that causes algal blooms. It’s a problem that cannot be ignored and, unless improvements are made, further restrictions may be needed.

The soluble test only shows a tiny fraction of the total P in our soils. The vast bulk remains insoluble and safe from leeching. Certain plants, such as buckwheat, have an ability to unlock some of this P. This is one of the reasons for having a proper crop rotation or multi-species swards. P is also stored in humus – the ideal place, as it is plant available and safe from leeching.

To maintain index 3 or greater, farmers need to apply more P than the crop requires to allow for soil P lock-up and leaching. This has a financial and environmental cost, but is the recommended practice in chemical agriculture.

Dr. Christine Jones’ peer-reviewed work highlighted another cost to this approach, which is the negative effect of acid-treated soluble P on the microbes that form humus.

Potassium doesn’t attract half as much of the negative attention that P does, but in potassium chloride or muriate of potash, the product of choice, we have a product that is potentially doing untold damage to our soils.

Image source: Shane Casey

Most people are aware of chlorine and its ability to sterilise microbes when added in small quantities to our drinking water, so it should be no surprise that it will do the same to the free-living nitrogen fixing bacteria or humus forming microbes required for healthy soil. This product is also used in the oil drilling industry because of its ability to stabilise clays, degrading their cation exchange capacity or ability to hold nutrients.

Earlier this year at the National Tillage Conference, Teagasc released trial data showing no difference in crop yield between muriate of potash and the much more benign sulphate of potash.

This is a perfect example of giving a misleading answer by asking the wrong question.

The real question needs to look at the effect on soil biology and clay structure over time, and account needs to be taken for the yield response that chlorine will give through releasing nitrogen from the microbes it kills and the nutrients released from the degraded clay particles.

In organic agriculture and in a more transitional biological system of agriculture (where crop yields can be maintained), a system exists that does not need to pollute our waterways and degrade our soils but, unfortunately, Teagasc seems to have no interest in researching these areas.

It is often said that a nation that destroys its soil, destroys itself. All real wealth originates from our soils and waterways, and everything else is either exploiting a finite resource or a confidence trick of an expanding money system.

Can we stand by while Teagasc remains a cheerleader for chemical agriculture, ignoring science and advising the degradation of our soils and waterways and, ultimately, our nation’s wealth?