Long-term Central Waikato summer-autumn rainfall and pasture growth trends. Are conditions for pasture growth changing over time?

Abstract

Farmers in the upper North Island are concerned about the poor productivity of their perennial ryegrass pastures beyond 3 years and suggest this is linked to a trend towards drier conditions for pasture growth during summer and autumn. To explore how conditions for pasture growth and survival have changed, trends in rainfall (measured and interpolated; c. 1954 to 2020), frequency of soil moisture deficit stress on pasture growth (1972-2020), and pasture growth rates (simulated 1977-2020, and measured c. 1979-2020) were compiled for summer-autumn months (November to April) for two Waikato locations: DairyNZ Ruakura/Scott Farm near Hamilton; and a commercial farm at Paratu Road between Morrinsville and Matamata. Significant negative linear trends were observed for interpolated rainfall (Paratu Road only), total stress days (both sites) and simulated pasture growth (both sites). No significant trend in measured pasture growth was observed for either site, suggesting adaptive management has cushioned the physical effects of harsher climatic conditions. The suite of adaptive management practices adopted on the Paratu Road farm is described. Analysis of decadal patterns indicated greater variability in rainfall in the decade 2011-2020 (coefficient of variation ranging from 32% to 36% depending on site and data source, versus ~ 22% in earlier decades) and a significantly higher number of stress days in the decade 2011-2020 compared with the 1970s and 1980s at Paratu Road. Further adaptation strategies will be needed to mitigate these most-recent trends, should they continue as predicted by climate change forecasts.

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

“…These farm systems factors are taken into account in the FVI modelling (Chapman et al, 2017). Thus, the gains in estimated profit resulting from breeding progress in the late‐season diploids were consistently strong, particularly in the upper North Island ($30 to $45/ha per year when DM yield only is used in the FVI model, Table 7) where summers and, especially autumns, are typically dry (Glassey et al, 2021) and feed demand of milking cows substantially exceeds feed supply from pasture.…”

“…The potential trait advantages of elite cultivar‐endophyte combinations may be suppressed by over‐riding environmental factors, where ‘environment’ includes management as well as physical factors. Factors contributing here could include: inter‐annual climate variability including more‐frequent and more‐intense droughts (Glassey et al, 2021); increasing soil compaction and declining soil structure under intensive grazing (Houlbrooke et al, 2021); and frequent over‐ or under‐grazing (McCarthy et al, 2014), all of which restrict pasture growth and potentially suppress the expression of DM yield advantages. Increased substitution of pasture in the diet by the industry trend toward higher rates of imported supplement use since 2000 (Chapman et al, 2020a) could also play a role.…”

Organising Committee Chair's address: Resilient pastures

“…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. This closely mirrors trends in south-eastern Australia where the key lesson has been…”

“…Resilient Pastures -Grassland Research and Practice Series 17: 7-14 (2021) that resilience to extreme climatic events is paramount (Cullen et al 2021). Farmers in affected areas, especially in Northland, are responding by moving away from perennial ryegrass (Glassey et al 2021;Jagger 2021;McCahon et al 2021). Simple conceptual models such as depicted in Figure 1 help guide the direction of change, but much better definition of what constitutes 'low' or 'high' stress, 'suited' or 'unsuited', 'alternative management' and 'better adapted' is needed to help decision-making at the individual farm level.…”

Greener Pastures: priorities for a low-footprint, high-value food producing future

“…Some factors behind declining pasture performance are known, for example the increasing frequency and intensity of droughts driven by climate change (Glassey et al 2021) which no current, conventional pasture technologies can withstand (Lee et al 2017). However, many questions remain.…”