We finally come to the third and final part to this series and we hope you enjoyed part 1 and part 2. To finish with a bang, we’ll be covering infrastructure projects, carbon storage and grasses for preventing laminitis and founder in horses.
The key ingredient in getting a successful result is in weed control. It is our view that the weeds that are now present on most sites, and which would not have been around thousands of years ago (such as Paterson?s Curse, Gorse, Ryegrass and Paspalum) will have a huge bearing on the success or failure of revegetation efforts. Even if the soil is being returned to the site and had no weeds present at the time of removal, there are likely to be many weeds that will emerge on the site simply because the site has been disturbed. Weeds are highly competitive with emerging native grass seedlings and need to be controlled in the early stages of establishment or poor results could occur
A good seeding mix should include some rapid establishing grasses such as Windmill grass (Chloris truncata) and Wheat grass (Elymus scaber) along with slower establishing species such as Kangaroo grass (Themeda triandra) and Wallaby grass (Rytidosperma spp).
If the site is highly likely to erode, or if a very rapid visual result is required, then a cover crop of a cereal like Ryecorn or Japanese Millet can be sown at 20 kg/ha along with the native grass mix. The cover crop should be mowed when it runs to seed to prevent those plants forming viable seed. These are annual grasses and will die off within a few months, but their root system will have contributed to hold the soil together and to protect the emerging native grass seedlings.
Grasses for carbon storage
Much has been written about the use of vegetation as a means of removing Carbon from the atmosphere and storing it in plant tissue. Most of the concentration of this work has been on the use of trees as carbon sinks as it has been very easy to calculate the amount of carbon stored inside a tree’s shoots, stems and leaves. Sadly, relatively little has been written about the use of grasses as carbon storage sinks. What has been written suggests that the grasses are even more effective at storing carbon than are trees. There are several reasons for this:
- Grasses are very effective at shifting carbon into the soil. Grasses for the most part have an annual root system with most of the smaller roots dying off each year and a new set of roots becoming established from the base of the plant. Thus each year many grasses will shed almost their entire root system into the soil which deposits large amounts of fibre (mostly carbon) into the soil and then the plants go about consuming more carbon as they build a replacement root system.
- Many native grasses form phytoliths (plant stones) that are solid aggregates of carbon within the leaves. These are not just ordinary bundles of carbon but are highly durable globules of bound carbon that are not able to break down for some thousands of years after production. While individually they are quite small, there are many produced and they can tie up large amounts of carbon for very long periods. What is interesting here is the work by scientists at Southern Cross University, NSW has shown that not all species produce phytoliths, but that the natives seem particularly adept and that trees are very poor at doing it.
- 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 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.
- When monitoring equipment is finally able to reliably and cheaply evaluate soil carbon levels it is likely to show that soil carbon under a well maintained native grass stand will be much higher than those under forests, that the levels continue to accumulate if grazing is managed well and that it is mostly held as long-term storage. All of which are likely to show that native grass pastures are an efficient and clever means of storing carbon.
Grasses for horse pasture
As a product of photosynthesis, introduced C3 (cool season) and C4 (warm season) grasses produce cellulose. When they are thriving, excess carbohydrates are stored. C4 grasses store these excess carbohydrates as starch but C3 grasses store these as fructan (a non-structural carbohydrate) which causes founder and laminitis in horses.
In our native Australian grasses, both C3 and C4, the excess carbohydrates are stored as starch, which is a more complex sugar and much less harmful to horses. These grasses are also rather high in protein.
The two grasses examined in the most detail are Wallaby grass (Rytidosperma geniculatum) and Weeping grass (Microlaena stipoides). The data for these grasses are interesting. When compared to the generally recognised threshold levels of concern for horses for NSC sugars such as Fructose and Glucose and total sugars these two native grasses come out very well.
The recommended thresholds are to keep NSC’s below 10 g/100g of the fodder which these two grasses easily fall under having contents for Fructose of less than 0.2, Glucose of less than 0.2 and total sugars of less than 1.0 g/100g. Thus these grasses are very well suited to horse consumption with next to no risk of serious conditions such as laminitis.
We really hope you have found the information collaborated in our 3 part article series very useful and informative. More detailed information can be found on our website. You can purchase seed for any of these fantastic native grasses from our online store.
Have a question for us? Feel free to leave a comment below if you have a question or feedback about this article. Or ask a question about grasses or how to grow them. Alternatively, you can always call us on 1300 4 73337.
Look forward to future articles by NativeSeeds!