We often think of pasture as grassy areas where cows, sheep or other animals graze, but if we take a closer look, there is a lot happening in the grassy paddock!
Pastures are ecosystems
An ecosystem is made up of animals, plants, bacteria and other microbes as well as the physical and chemical environment they live in. Understanding this complex interplay of living and non-living components is vital to pasture management and raising healthy, productive livestock.
Pasture food webs
Like other ecosystems, pastures are part of a food web. Pasture grasses are primary producers – they make their own food through photosynthesis. Chlorophyll (the green pigments) within the plants’ leaves absorb energy from sunlight. That energy is used to process carbon dioxide from the air and water from the soil into oxygen and glucose (carbohydrates).
Plants use the carbohydrates to create cellulose, starch and other compounds that make up their structures and biomass. Livestock tend to be the herbivorous consumers in the food web, although pests such as field crickets and possums also consume pasture grasses. Decomposers like bacteria, earthworms and dung beetles break down dead plant matter and other organic materials. They play an important role within the food web as decomposition returns nutrients to the ecosystem. If you consider that one dairy cow produces up to 60 kg of manure each day, that’s a lot of organic material to recycle!
Diverse pasture plants
Pasture is often made up of a mixture of plants including grasses, legumes and herbs. Pasture species tend to be perennial, meaning they grow all year round. Specific cultivars are chosen to suit the local growing conditions. For example, plantain and chicory tend to grow well in warm, dry summer conditions when other species such as ryegrass are not growing as well. A diverse pasture – also called a mixed sward – provides livestock with a variety of minerals and nutrients.
Some of New Zealand’s common pasture species are featured in this interactive.
New plant species and cultivars
Pasture species have changed over time. When New Zealand farmers discovered that native grasses were not suitable for grazing animals like cows and sheep, they imported English grasses and clovers.
Over the decades, research and development has provided information about the types of plants that best fit seasonality, soil type, regional climate and animal needs, along with economic and environmental considerations. Pasture plants usually have a number of cultivars available – the physical characteristics of the individual plants are important to ensure persistence and productivity. For example, a ryegrass cultivar used on an irrigated dairy farm would not be as well suited to dryland paddocks.
Although pastures are ecosystems with their own food webs and complex dynamics above and below the ground, they are actually managed ecosystems. Farmers manage pasture plant species, stocking rates, fertiliser applications, irrigation, grazing rotations and much more.
Good pasture management is incredibly important for optimal production of the land and the animals it supports. Farmers need to be aware of what plant species are growing, how much is growing and about the feed quality – the energy value of feed. Feed quality of pasture species changes during the seasons. For example, ryegrass feed quality falls in late spring when seedheads start to develop.
Farmers also need to manage what happens below the ground. Pasture plants rely on good soils – the right level of nutrients and fertilisers. Soil structure helps to regulate the movement of air and water and influences root development.
Find out about some of the innovations happening with pasture grasses:
- Grasslanz – Innovative Plant Technology
- Ian Yule – Pasture Meter
- Ian Yule – Aerial Scanning for Pasture Analysis
Read about seed banks and New Zealand’s Margot Forde Genebank. Pasture species may need to be changed due to issues like climate change and disease. The Germplasm Centre’s grassland seed collection acts as a type of insurance against these issues.
This resource has been produced with the support of DairyNZ.