Feeding dairy cows on monoculture rye grass pastures not only adversely affects their health and milk production, but may also be an animal welfare issue, says Dr Christine Jones – an international authority on soil health and profitable farming systems.
“Cows don't like eating ryegrass, which has a sour taste and a crude protein content far higher than required by lactating dairy stock.
“Excess nitrogen results in elevated levels of blood urea nitrogen and milk urea nitrogen, which have been linked to an increase in lameness, mastitis and infertility,” says Christine, who was in New Zealand in May to conduct a series of seminars.
AgriSea New Zealand Limited hosted Christine's ‘Farming Profitably within Environmental Limits' seminars – and general manager Tane Bradley says the company was delighted to give farmers the opportunity to hear her speak at four different venues.
“Along with her international experience, Dr Christine Jones is also well aware of NZ soil conditions, has conducted research on NZ farms and understands our environmental constraints.”
Christine says that in addition to animal health issues, excess dietary N is excreted as urinary N causing environmental pollution.
New Zealand's low diversity shallow-rooted ryegrass/clover pastures provide a monotonous diet for cows. In contrast cows that happily graze on swards containing herbs such as chicory, plantain, Lucerne and red clover have improved health and milk production, while excreting significantly less urinary N.
“In Britain there are some pastures with 400 different species of plants and meadows with up to 200 different species are not uncommon.” For some reason New Zealand agriculture has adopted a monoculture approach, relying almost exclusively on ryegrass and clover. “Inexplicable, even when farmers do plant another species, they seldom mix it with their pasture, but grow it as a separate crop.”
Relying on rye grass makes farming vulnerable to extremes of weather, and the grass doesn't produce well year-round.
Christine is also concerned at New Zealand agriculture's heavy reliance on inorganic nitrogen fertiliser. Globally, more than $100 billion of inorganic nitrogen fertilisers are applied to crops and pastures every year. Between 10 and 40 per cent of the applied N is taken up by plants. Much of the remaining 60 to 90 per cent is returned to the atmosphere as ammonia or nitrous oxide – or leached to aquatic ecosystems as nitrate.
Due to its high mobility, inorganic nitrogen has become a key stressor for terrestrial, freshwater and marine environments in many locations around the world – including New Zealand.
“According to Statistic New Zealand, NZ imported 650,000 tonnes of urea in 2015-2016 at a cost of $281 million. Volatilisation and leaching losses of 60-90 per cent would equate to annual wastage somewhere between $168 million to $252 million, representing a high economic cost to farmers.”
Those figures don't take into account the urea produced in this country at the Kapuni ammonia urea plant in South Taranaki.
The cost to the wider environment are huge, says Christine. “Removing toxic nitrates from drinking water, for example, has been estimated to cost up to $10.7 billion.”
While fertiliser application rates have decreased in most OECD countries in recent years, the amount of inorganic nitrogen applied to New Zealand farms increased 41 per cent between 2000 and 2010.
In contrast France, Germany and the United Kingdom have maintained high yields with 40 to 50 per cent less fertiliser than used in the 1980s.
Raft of benefits
Many New Zealand farmers have come to believe that they can't grow grass without using inorganic urea. However, Christine says the best thing they could do for the health of their soils, pastures and animals, and for the quality of products they produce, is to reduce their reliance on N.
“Farmers who transition to biological fertilisers, which support soil life, are amazed at the results achieved.” Restoring biodiversity to agricultural soils brings a raft of economic and environmental benefits, says Christine.
In fact she believes the future prosperity of New Zealand relies on using ecologically sound agricultural production methods.
“Enhanced above and below-ground diversity may well be the key to the restoration of profitable, environmentally friendly farming.”
Farming within imposed environmental limits, which include limits on nitrogen application, won't mean an end to profitable farming.
Christine's says two steps are required. “Incorporate as much pasture diversity as possible, particularly warm and cool season herbs and variety of grasses.
“Replace inorganic N with biology-friendly products to enhance the innate capacity of soil microbial communities to fix atmospheric nitrogen. In the same way as it is important to “feed the rumen not the cow”, it is also important to “feed the soil microbiome, not the plant”.