The facts about nitrogen in horticulture

11 Dec 2018


Stuff recently gave space to an opinion piece from Glen Herud, a dairy farmer, which had a number of inaccurate references to the use of nitrogen in horticulture and horticulture practices in general (Stuff, December 4, 2018).

 It is important to note, the primary industries are working together to address both the real and the perceived impacts of food production on the environment. At Horticulture New Zealand, we are sitting down and talking to key Government Ministers and their officials from the relevant government agencies to look at the best ways to clean up waterways and address climate change. This is how the best policies will continue to be made.

 In his opinion piece, Mr Herud’s numbers and references to research are unsubstantiated. I don’t want this to be a science class, but there is a lot of misinformation about nitrogen being spread around and it is essential to deal in facts, backed by science.

 For example, it is not true that “market gardening leaches three times more nitrogen than dairy farming”. Nitrogen loads are used as the measure for water quality effects and the load from vegetables is just three percent of the Waikato and Canterbury nitrogen loads.

 Fruit and vegetable crops need essential elements, which they take up from the soils they grow in. Some of these are also vital for human health and we get them from the foods we eat. This includes nitrogen, which is an essential component of all proteins in the human body.

 Horticulture New Zealand has commissioned research to improve the management of nitrogen, phosphorus and sediment in commercial vegetable growing. We have modelled and measured leaching from a range of vegetable growing systems, including those grown in market gardens, intensive vegetable rotations growing leafy greens for domestic supply, and in arable style rotations, including process vegetables and fodder crops. What we conclude from this is that when we grow crops in winter, whether they are to feed people or animals, there is a higher risk of leaching due to the rain. This risk of leaching needs to be manged.

It is the load of nitrogen that is discharged to nearby waterways, not the average leaching concentration, that may have an effect on water quality.

 In New Zealand, only 50,000 hectares is used in commercial vegetable production (just 0.2% of New Zealand’s total land area), predominantly for domestic supply. These vegetables are of vital importance to the health of all New Zealanders. The environmental impact of growing our food is very small on the quality of New Zealand’s waterways overall; but it can have local water quality effects. That is being managed, and growers have systems in place, such as sediment traps, buffer strips and extensive riparian planting, to protect waterways.

  Our vegetable growing rotations have been influenced over time by Māori, Chinese, Indian and European traditions. In his article, Mr Herud makes the case for the European style mixed growing system. In these rotations a range of crops are grown, including some vegetable crops such as peas and potatoes; seed crops; arable crops such as wheat; and animal feed crops; as well as pasture and fodder crops. If more fruit and vegetables are grown in New Zealand, as part of our transition to a low emission economy, these will be crops for export, and some of these may well be best suited to growing in a mixed farming systems.

 We also value the other growing traditions that are reflected in market gardening and intensive vegetable rotations. In these rotations we grow a wide range of vegetables including leafy greens, mainly for domestic food supply. The market garden and intensive vegetable style rotation doesn’t include animals, and usually occurs on small blocks rather than as part of larger farming systems.

 Our growers are predominantly intergenerational family businesses who want those businesses to keep providing a good living for their future generations. Their business is providing healthy food to New Zealanders, while maintaining the health of their land. Horticulture New Zealand is committed to working with growers to support their implementation of good management practices to ensure good environmental outcomes for all.

We are happy to talk to anyone at any time about the steps being put in place by growers to meet the environmental expectations of both regulators and consumers. 


- Mike Chapman, CEO