Is the grass greener under irrigation?

With a changing New Zealand climate causing more frequent and more severe dry spells, including in regions previously seen as less vulnerable, the reliability of supplying food to meet our goals and expectations is in question. As we are fortunate to have available freshwater, irrigation has been widely used in certain regions to combat the dry. If future irrigation is proposed, farmer uptake is crucial to the success of the scheme, but farmers need to understand if it can work for them or if the required change is too great.

The problem is, how does a pastoral farmer, when presented with or investigating an opportunity for irrigation water supply, know whether taking up the opportunity will provide an overall benefit? Not just to the farmer but will it be sustainable for the environment and their community hence the question of Is the Grass Greener under Irrigation?

The aim is to provide an informative resource for would-be irrigation users by firstly understanding the climate predictions, available water and current Irrigation in New Zealand, Then the known impacts and opinions of irrigation are analysed before answering the research question as to the overall benefit, or otherwise of irrigation to pastoral farmers.

Research methodology involves a literature review, to ensure context for the topic and to critically analyse existing research and studies relating to the report objectives. This is followed by a series of semi-structured interviews with professionals and a survey of existing pastoral users of irrigation with thematic analysis used to identify the key themes.

Key findings include:

New Zealand is experiencing climate change meaning the North and East of the country will experience a higher frequency of drought (National Institute of Water and Atmospheric Research, n.d.) but fortunately New Zealand has a relative abundance of freshwater at four times the global average (Business and Economic Research Ltd, 2019).

Over 900,000 hectares of land is currently irrigated in NZ (Irrigation New Zealand, n.d.). It was found that the introduction of irrigation often brings about three waves of ownership change and land use change (McCrostie Little & Taylor, 2001). The required change can have a strong impact on lifestyle and well-being.

Nitrate leaching and unsustainable water use are widely regarded as the major concerns resulting from agricultural intensification (Te Ara, 2024). It is argued that whilst irrigation enables agricultural intensification, irrigation is not the main contributing factor to poor water quality however, improved irrigation management and technology adoption can significantly reduce the overall environmental impact.

Irrigation contributes significantly to the economy with estimates that irrigation, including beyond the farm gate, adds at least $5.4 billion to NZ’s GDP (Corong et al, 2014, as cited in Irrigation New Zealand, 2018). In dryer regions, irrigated land produces three times as much produce as the equivalent area not irrigated (Heiler, 2008, as cited in Te Ara, 2024). This supports the primary purpose of irrigation in pastoral farming: Improving pasture reliability and productivity (Mcbride 1994). The additional feed produced under irrigation comes at a greater cost so ensuring a high return from that production is vital.

The recommendations to would-be irrigated pastoral farmers are to consider if adopting irrigation and potentially changing their farming system and lifestyle will align with what is important to them. Also, measuring and recording data is imperative to understand how irrigation will affect the property. Lastly, before adopting irrigation, farmers should complete a cost-benefit analysis of the many variations of their existing system and potential systems and land uses under varying proportions of areas irrigated.