Warm season grass pastures
By Lisa Castleman, Senior Land Services Officer, Agronomy
If you have been receiving rainfall recently then your paddocks may be looking green and lush. Many of the sub-tropical grass species including the warm season native grasses have come into head now, with their seedheads gently billowing in the breeze.
Depending on the species, the pastures vary in their height from low if they have a prostrate habit, to short at under 30cm, to tall at over a metre. What also varies is the quantity of feed on offer to livestock (measured in tonnes of green Dry Matter/ha), the pasture quality of that feed (energy, protein and fibre) and the palatability or attractiveness to stock.
These variables in pasture quantity and quality all depend on the species present and whether the plant is in its vegetative state (growing leaf and stem) or reproductive state (usually the stem elongates followed by a seedhead becoming visible then flowering and setting seed). The density of a pasture is also determined by the number of plants present, how many shoots or tillers each plant has, how many leaves have grown and other factors such as a soil’s fertility and underlying soil health with an absence of soil constraints.
Are the pastures doing what they should be doing, at this time of year?
Yes, absolutely…despite many dry months last year, the pastures have had a chance for growth over the summer where rainfall has occurred regularly and where rainfall events have exceeded 10mm in a fall.
Point to note-rainfall events less than 10mm tend to evaporate quickly from the soil surface and do little to relieve moisture stress let alone result in pasture growth.
Pasture species coming to the end of their summer growth period and with seed-heads now clearly visible from the roadside and in the paddock, include the pasture species suited to the sub-tropical climate - Rhodes grass, Setaria, Paspalum dilatatum and Couch.
Rhodes grass (Chloris gayana) has differing types and cultivars on offer (both public and private) when purchasing seed, is well regarded for dry matter production, palatability to stock, ease of establishment (although the seed is light and fluffy), spreads by runners and drought tolerance.
More information on Rhodes grass can be found on the pastures australia website on keys.lucidcentral.org with a detailed page on Rhodes grass and at https://www.dpi.nsw.gov.au (Agnote DPI-298).
Grasses can be grouped according to their growth pattern, when they mature and the climate they have adapted to. In New South Wales on the North Coast, we have many grass species that were well adapted to our climate, the soils and our native grasslands. You may be familiar with some or all of them below in Table 1. Warm season perennial species
Species | Common name | Height of grass incl. seedheads (metre) | Forage value | Native species present in Native Grasslands | Drought tolerance |
Warm season perennials | |||||
Themeda australis | Kangaroo grass | 1.5 m | Low | Yes | high |
Sorghum leiocladum | Wild sorghum | 1 m | Low | Yes | moderate |
Aristida ramosa | Wiregrass (Purple) | 0.25-1.0 m | Low | Yes | high |
Cymbopogon refractus | Barbed wire grass or Lemon scented grass | 0.3-1.5 m | moderate (when young) low at maturity | Yes | high |
Bothriochloa macra | Redgrass or Red-leg grass | 0.3-1.0 m | moderate | Yes | high |
Sporobolus elongatus | Slender rat’s tail | 0.5-1.0 m | moderate (when young) low at maturity | Yes | moderate |
Eragrostis leptostachya | Love grass | 0.2-1.0 m | moderate | Yes | moderate |
Eragrostis curvula | African love grass (invasive, classed as a weed) | 0.2-1.2 m | Low | NO | moderate |
Chloris truncata | Windmill grass | 0.1-0.5 m | Low | Yes | moderate |
Dichanthium sericeum | Queensland Bluegrass | 0.3-1.2 m | moderate | Yes | high |
Panicum effusum | Hairy panic | 0.7 m | moderate to high | Yes | high |
Hyparrhenia hirta | Coolatai grass (invasive, classed as a weed) | 0.6-1.5 m | low | NO | moderate |
Paspalum dilatatum | Paspalum (pasture species and environmental weed where not wanted) | 1-2 m | high | NO | moderate |
Paspalum mandiocanum | Broad-leaf Paspalum or Warrel grass (shade-loving environmental weed where not wanted) | >1 m | low | NO | moderate |
Cynodon dactylon | Couch grass or Bermuda grass | 0.1-0.3 m | high | Yes | high |
Setaria (Setaria sphacelata var. sericea) is not native to Australia but originated on the African continent. Its growth habit is well suited to the moist sub-tropics of the North Coast and Mid Coast in NSW, where there is more than 1000mm of average annual rainfall. It is a perennial species and cultivars differ in their frost tolerance, winter growth, drought tolerance, flood tolerance, seed production and oxalate levels. More information can be found on Setaria for coastal pastures at https://www.dpi.nsw.gov.au (Agnote DPI-223).
A new cultivar of Kikuyu (Pennisetum clandestinum) was bred for disease resistance to ‘kikuyu yellow’ and black spot on the leaf, suitability for the dairy industry and grazing by cattle, and released in 2023. I recently stood in a new stand of Fulkerson Kikuyu that was above my knees, dense and lush, waiting for a new mob of cattle to turn up. In good red soil on the Alstonville plateau, with planned weed control, the pasture growth of this new Kikuyu stand was truly phenomenal. Kikuyu has a seedhead which is not highly visible, but it still has a mature stage that follows the leafy green vegetative stage. Kikuyu is not a native species either and originated in the Belgian Congo in central Africa. More information can be found at https://www.dpi.nsw.gov.au (Agnote DPI-290).
There is a group of grasses known as the Year long green perennials, which include species such as the highly regarded Microlaena or Weeping grass Microlaena stipoides and Wallaby grass Austrodanthonia racemosa.
Another group of grasses is the Warm season annuals such as Liverseed grass Urochloa panicoides. Another grass species in this category is the weedy and invasive grass (native to America not Australia) Feathertop Rhodes grass Chloris virgata.
Species which belong to the groups of the Cool season perennials such as Wheat grass Agropyron scabrum, or the Cool season annuals such as Barley grass Hordeum leporinum are not going to suit the North Coast sub-tropical climate and are going to be less prevalent, if they occur at all in our region.
So, you may have one or more of the grass species described above in Table 1 or the article, but how does the time of year impact on the pasture growth and this translating into feed available for stock?
Turning Pasture Growth into Feed
Table 2. Growth rates (kg/ha/day) for Setaria, Rhodes grass, clover in North Coast, NSW | ||||||||||||
Growth rates (kg/ha/day) | ||||||||||||
J | F | M | A | M | J | J | A | S | O | N | D | |
Setaria, rhodes grass, clover – Standard year | 30 | 55 | 45 | 25 | 6 | 2 | 2 | 4 | 8 | 20 | 28 | 30 |
Setaria, rhodes grass, clover – Good year | 48 | 132 | 108 | 60 | 18 | 6 | 6 | 12 | 14 | 34 | 48 | 48 |
Setaria, rhodes grass, clover – Poor year | 12 | 22 | 5 | 3 | 1 | 1 | 1 | 1 | 3 | 8 | 11 | 12 |
Discussion of the data in Table 2. Growth rates above:
Look how pasture growth takes off in October (weather permitting) regardless of the season and then continues to increase into November, with growth excellent and continuing into December and January. In a good summer season (with regular and significant rainfall events and warm temperatures), the pasture growth reaches its peak in the month of February and even in March the pasture growth exceeds early summer. The month of April can be very good for pasture growth but is highly variable between seasons, it just depends whether the rain continues as the nights and mornings cool down and daylength begins to shorten. A cool, dry start to autumn with early frosts can slow pasture growth very suddenly and/or reduce the quality of standing feed quickly.
The magical figure for pasture growth rates is often described as 20 kg/ha/day or greater so look in the table at when these growth rates occur. Of course, matching your stocking rate to these growth rates to take advantage of the resource is key. And defining clear and realistic goals for your livestock production system is important. A producer can have realistic production goals which allow for seasonal variability, the approach to risk is a very personal decision. Many producers would prefer to carryover excess feed than be caught with insufficient feed when it becomes dry and or cold. Having access to machinery, equipment and/or reliable contractors means that other winter options such as sowing ryegrass or oats, or feeding out hay or silage, can be utilised to fill the winter feed gap.
But for now, if your grassy pastures have been growing well, are tall in height, bulky and maturing with seed heads visible, take advantage of peak pasture growth rates in February and we will remain hopeful this will continue into March.
References:
NSW WeedWise for descriptions of African love grass and Coolatai grass
Regional pasture growth rates | EverGraze More livestock from perennials
Grasses of Coastal NSW (Rose, H. & Rose, C.), 2020, Department of Primary Industries, Tocal College, Paterson. https://shop.regional.nsw.gov.au/
For more information
Contact a member of the Sustainable Agriculture team on 1300 795 299 or Lisa Castleman directly on 0460 898 096 or by email.