Climatic factors influencing New Zealand pasture resilience under scenarios of future climate change

Grass and Forage Science

Wims

Ludemann³

et al. 2022

Perennial ryegrass (PRG, Lolium perenne L.) breeding effort in New Zealand (NZ) has increased since c. 1990, resulting in greater functional trait diversity (e.g. heading date, ploidy, and associated Epichloë endophyte strain) in commercial products. This study quantified the variation, associations and interactions in dry matter (DM) yield, nutritive value and persistence‐related traits among commercial cultivar‐endophyte combinations released between 1973 and 2012, as a basis for assessing gains in value being delivered to the pasture‐based livestock industries. Twenty‐four or 28 combinations were compared over 3 years in two trials in each of two regions: Waikato in northern NZ (dryland), and Canterbury in central eastern South Island (irrigated). Cultivar‐endophyte combinations were sown in mixtures with white clover, and pastures were intensively grazed 8–11 times per year by dairy cows. Principal Component Analysis identified 4 distinct clusters for the DM yield variables and for metabolisable energy (ME) content in each of the four trials. A broadly‐adapted group of three late‐season flowering, AR37‐infected diploids with NZ and Spanish breeding backgrounds dominated the highest‐yielding clusters. Tetraploids dominated the high ME content clusters. Interactions with region were observed throughout the data set: the strongest of these was driven by endophyte strain effects in Waikato. High‐yielding cultivar‐endophyte combinations in these trials were also generally high‐yielding in the standard cultivar merit testing system operated in New Zealand, as interpreted via the DairyNZ Forage Value Index. However, alignment was poorer for medium‐ and lower‐yielding cultivar‐endophyte combinations. Several implications for forage evaluation methods and end‐user industries are identified.

Section: Discussionmentioning

confidence: 99%

The contribution of perennial ryegrass (Lolium perenne L.) breeding to whole pasture productivity under dairy cattle grazing in New Zealand. 1. Variation in yield, nutritive value and persistence‐related traits

Grass and Forage Science

Wims

Ludemann³

et al. 2022

“…Attention to mid‐season diploids has been renewed recently. One recent release ranks in the 4‐star band in the UNI where the prospects of more severe summer‐autumn droughts under climate change predictions (Keller et al, 2021) suggest a greater role for earlier‐flowering material with strong yielding ability from winter to late spring when soil moisture is reliable and warmer winters can support higher growth rates.…”

Section: Discussionmentioning

confidence: 99%

The contribution of perennial ryegrass (Lolium perenne L.) breeding to whole pasture productivity under dairy cattle grazing in New Zealand. 2. Rates of gain in production traits and economic value

Grass and Forage Science

Ludemann²,

Wims³

et al. 2022

Perennial ryegrass (Lolium perenne) plant breeding has delivered several high performing and broadly adapted cultivar‐endophyte (Epichloë) combinations for the New Zealand pasture‐based livestock industries. However, the trends in key traits and the potential economic value being added to farm systems have not previously been addressed systematically. Rates of gain in yield, nutritive value, phenological and morphological traits, and the economic value of those traits, were estimated among and within ryegrass functional groups (heading date, ploidy) traded commercially between 1973 and 2012. Whole pasture dry matter yield improvements of c. 80 and 60 kg DM/ha per year were identified in in late‐season heading diploids and tetraploids respectively. Trends in metabolisable energy were negative within functional groups, but positive when all cultivar‐endophyte combinations were included in the analysis due to the addition of tetraploids and late‐season heading diploids from the mid‐1990s. The estimated trend in overall economic value (all cultivar‐endophyte combinations included) was $7/ha per year based on DM yield only, about half the rate of gain previously estimated using small‐plot merit testing data. The trend increased to $15/ha per year when ME was included due to the emergence of commercial tetraploids from the early 2000s onwards. Estimated economic gains were high within late‐season heading diploids and tetraploids but not mid‐season diploids. These trends suggest that, if high performing cultivar‐endophyte combinations had been adopted in New Zealand dairy systems, then pasture utilization should have increased by ~1 t DM/ha above the current industry average. Reasons for this apparent discrepancy are discussed.

“…The most significant global force driving change in New Zealand agriculture is climate change, via New Zealand's commitment to the Paris Agreement to reduce carbon (C) emissions to net zero by 2050, C-neutral strategies being implemented by some of our largest customers (e.g., Nestle 2020), and the physical impacts of climate change on conditions for plant growth (e.g., Keller et al 2021). Of direct and significant relevance to the livestock industries are the methane emission reduction targets proposed by government, of between 27% and 47% below 2017 levels by 2050.…”

Section: Pasture-based Livestock Systems Experiencing Significant Changementioning

confidence: 99%

“…This conclusion holds across all livestock sectors in New Zealand, as explicated by Stevens et al (2021). 'Resilience' in the context of pastures includes mitigating the effects of: increased climate variability and the underlying drying and warming trends predicted by climate change models (e.g., Keller et al 2021); higher pest, weed and disease burdens, also related to changes in climate (e.g., Mansfield et al 2021); and lower inputs of fertiliser, herbicides and other synthetic products that are subject to changes in regulation and/ or customer demands.…”

Section: Resiliencementioning

confidence: 99%

“…Climate change projections indicate that temperate pasture species will experience increased abiotic growth stresses across much of the North Island (Keller et al 2021), while damaging levels of several key insect pests will be exceeded more often (Mansfield et al 2021). Recent trends toward hotter, drier summers/ autumns in Waikato have been highlighted by Glassey et al (2021), including the observation that six out of the last 10 years in Waikato have brought significant summer/autumn droughts.…”

Section: Job Security: Pasture Persistence Adaptation and Resiliencementioning

confidence: 99%

See 1 more Smart Citation

Organising Committee Chair's address: Resilient pastures

2022

NZGA R&P Series

High value animal products from New Zealand’s pasture-based livestock systems have consistently earned $25-$30B in export earnings per year for the country over the past 5 years (Ministry for Primary Industries 2021). Total earnings from dairy and meat of $30.5B in 2020 equate to 35% of New Zealand’s total goods and services export earnings of $86.4B. The importance of this revenue to the national economy has been shown in stark relief recently with the Covid-19 pandemic substantially reducing the earnings generated by other key export sectors such as tourism and international education. While our pasture-based livestock industries have ridden the coronavirus wave well compared with other sectors of the economy, they are facing change at a scale and pace not seen since the far-reaching reforms to the economic settings for agriculture introduced by the Lange Government in the early 1980s. Locally, the ramping-up of government environmental policies beginning c. 2011 has resulted in stringent regulations controlling the amounts of nitrogen (N), phosphorus (P) and sediment that can be discharged into freshwater from farm systems. The most recent iteration in this policy sequence includes new National Environmental Standards for Freshwater, and the new National Policy Statement for Freshwater Management (NPS-FW), which came into force in September 2020. These policies reverse the trends of the past two decades when agricultural productivity grew substantially in the virtual absence of regulation to control the environmental externalities of systems intensification. While the initial impacts on land use and farming practices have been localised (e.g., in the lake districts of Rotorua and Taupo), disruption to the farm systems that have emerged over the past two decades, especially intensive dairy systems, will be widespread in the future. For example, Doole et al. (2021) estimated that the new standards introduced in 2020 will require about 40% of New Zealand’s 11400 dairy farms to reduce nitrate leaching by an average of around 42% relative to requirements in previous iterations of the NPS-FW. The most significant global force driving change in New Zealand agriculture is climate change, via New Zealand’s commitment to the Paris Agreement to reduce carbon (C) emissions to net zero by 2050, C-neutral strategies being implemented by some of our largest customers (e.g., Nestle 2020), and the physical impacts of climate change on conditions for plant growth (e.g., Keller et al. 2021). Of direct and significant relevance to the livestock industries are the methane emission reduction targets proposed by government, of between 27% and 47% below 2017 levels by 2050. Meanwhile our international competitors have been steadily closing the gap in costs of production with New Zealand, and now have other fields on which to out-compete us (e.g., in C footprint) unless we can keep pace.