NFU Cymru National Environment and Land Use Adviser, Rachel Lewis-Davies, writes about the issue of air quality and reducing ammonia losses:
The issue of air quality is increasingly in the news headlines with ammonia (NH3) being a particular focus. This is because, when combined with other ‘industry pollutants’ such as carbon dioxide and sulphur dioxide, it is a major atmospheric pollutant which is harmful to human health and linked to major cardiovascular and respiratory disease. Ammonia also has environmental impacts including acidification and eutrophication of soils, habitats and freshwaters.
In Wales, agriculture contributes to over 85% of ammonia emissions, originating largely from manure management and from the application of urea based fertilisers. Welsh Government has recently published guidance on reducing ammonia losses from agriculture in Wales. Available on the Welsh Government website, the guidance is intended to supplement the existing Code of Good Agricultural Practice, providing practical ammonia management options for Welsh farmers.
The Code identifies that losses can occur at each stage of manure management. Reducing ammonia losses, therefore, requires a focus in key areas including livestock diets, livestock housing, manure and slurry storage, application to land as well as inorganic fertilisers.
Livestock excrete more than half the protein intake in feed in the form of different nitrogen compounds. Improving protein efficiency within livestock diets by trying to match the protein content of diets to the expected level of production and particular growth stage of the stock can, therefore, help reduce ammonia emissions.
In terms of livestock housing, the basic principle is to reduce the area of ammonia emitting surfaces. The covering of slurry stores is also effective in reducing the loss of ammonia, whilst with manure storage the aim should be to cover or reduce the surface area in contact with air. Spreading using precision equipment such as trailing shoe, trailing hose and injection systems under windless, cool and humid conditions - and avoiding winter conditions of frost, snow and heavy rain – will optimise nutrient uptake.
Applications of mineral fertilisers are thought to account for 18% of ammonia emissions from agriculture. Applying to meet crop needs and when weather and soil conditions are right can help as can regularly maintaining and calibrating application equipment. For more detailed information refer to the Welsh Government Guidance.
Going forward we understand that Welsh Government intend to consult on a Clean Air Plan later this year. This will set out proposals for policy measures to improve air quality and associated public health and environmental outcomes across Wales.
It is important to highlight that nitrogen fertiliser is a crucial nutrient for good healthy crops. Most agricultural soils do not contain enough naturally occurring nitrogen to meet crop needs, so supplementary applications using manure or manufactured fertilisers are vital. Investment in infrastructure and technologies to enable improvements to be made to reduce ammonia emissions are going to be crucial recognising that, in many cases, the cost of these improvements greatly outweigh any potential business gains.