Carbon storage – native vs. introduced grasses for carbon storage
What effect does carbon have on the environment?
Carbon pollutes our air, increasing the greenhouse effect or global warming. Temperatures are said to rise. Polar ice caps said to melt. But it also plays a detrimental role on the environment and our own health.
So what does this have to do with grasses?
Just about everyone knows that trees store carbon. But did you know that grasses also play a major role in carbon storage?
Ok, so why native grasses and not just any grass?
When trees break down, either rapidly in a fire or slowly through death and decay, the carbon that was in their foliage is returned to the atmosphere. Thus tree carbon is only a relatively temporary solution to carbon sequestration.
When grasses die, the leaves decompose and also release carbon back to the atmosphere. So the selection of long-lived grasses is important if your aim is to provide a long-term carbon sink. Clearly native grasses are highly persistent in their natural environment and are a natural choice for this purpose.
Ok, ok? so what does this have to do with me?
Well, possibly nothing or possibly a lot. We just hope that with this valuable nugget of information, you will at least consider (or continue to consider) native grasses as an alternative to the cheap, low quality introduced grasses that can actually be harmful for our environment both in terms of carbon and in terms of fuel load for fires (which you learn more about from Bob Myers in this video).
If you have any questions, please don’t hesitate to call us on 1300 4 73337 or email to firstname.lastname@example.org !
Native Grasses for Erosion Control
The control of soil losses following disruption is vital in preserving soil volume. Once lost to a property, soil is not replaced as the weathering processes required to break down stones and rocks is far too slow to quickly and adequately return soil to eroded landscapes. While it may be possible to build the organic content of soil and to capture some soil particles as they move across the soil, these additions do not, of their own, create new soil. Thus it is vital to not lose soil off a property.
Causes of erosion
Erosive forces such as wind and heavy rainfall cannot be stopped as they are outside of human control but their effects can be minimised by providing the soil with a full grass cover at all times. Having a perennial grass cover that is adapted to the environment is an ideal method of reducing erosion as long as it is accompanied by appropriate grazing management to help to retain a full cover at all times.
Establishing a grass cover on exposed or disrupted areas is an essential part of good soil management and erosion control. But achieving this with grasses that are sometimes slow to establish is a difficult operation. For example, while it might be ideal for an area to have a cover of spear grass and wallaby grass, these two grasses are very slow to establish and their seedlings will not hold the soil together in any appreciable way for a number of months after sowing.
So how do we hold the soil together in the meantime? We often suggest sowing with a cover crop of a cereal which will establish quickly and provide a fibrous root system that will hold the soil in place. If the cover crop is not sown too densely it will not be too competitive with the new seedlings and they will develop underneath the cereal crop almost unaffected. Care needs to be taken using this approach not to allow the cereal crop to go to seed, otherwise this will become next years weed problem and will continue then to be competitive with the native grass ground cover.
Cover crops such as Ryecorn, (or cereal rye), Japanese Millet, Barley, wheat and so forth can provide a good cover for an emerging grass. We have successfully established both wallaby grass and weeping grass underneath covers of barley and wheat to control erosion, and clients have also been very successful with covers of Jap Millet and Ryecorn.
Care needs to be taken with erosion control to sow at a low enough rate – 20 kg/ha of the cover crop is usually recommended, but it can go up to 30 kg/ha, but no more. Where possible the cover crop and the sown grass should be sown in alternate rows of a combine as if they are sown in the same row they will be competing with each other for water and nutrients.
Once the cereal crop has been mowed off and has died at the end of the first year, there should be numerous small plants of native grasses now able to access light, water and nutrients.
For grasses other than weeping grass and wallaby grass this may be more difficult, especially for the upright and faster-growing plants such as Barbed wire grass and Kangaroo grass.
We are often asked about the use of sprayed on mulches for erosion control. Results have been patchy with sprayed on mulches and it seems that the inclusion of high contents of paper cause many issues with successful establishment. We have had some successes with paper mulches, but they are not frequent and we have much higher rates of success with loose fibre mulches. We have also had success with deep mulches of materials such as potting mix or loose composts with depths of up to 50 to 60 mm still yielding positive results.
Drought tolerant grasses
Native grasses are adapted to drought
Australia regularly suffers from severe droughts and low rainfall. Australian native grasses are well adapted to this and are usually the first grasses to recover after a drought. They have a variety of mechanisms for drought avoidance, either through entering a prolonged dormancy, or through having a below-ground crown which is capable of surviving drought and grazing. These grasses are usually advantaged by the impact of drought and become more prevalent following the breaking of the drought. Once grasses are established they can survive with minimal watering or irrigation.
When native grasses are used for lawns, landscape and amenity uses, there is a much lower (sometimes nil) watering requirement. In pastures, native grasses have a far greater capacity to tolerate drought without the need to resow the pasture following the breaking of the drought. In horticulture, supplementary irrigation in the space between the rows of vines or tree crops may not be needed.
Native grasses tolerate high summer temperatures
Australian summers have high temperatures and native grasses have evolved to be able to tolerate these conditions. Many grasses, such as wallaby grass, retain green colour and some growth throughout the summer. So several native grasses are suitable for lawns and amenity areas where a green colour is desired throughout the year. Many of these grasses are also able to respond to summer rainfall by retaining this slow-growing, but activestate over the summer period.