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Nutrients for Australian Natives
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Posted by nemo Rural NSW (My Page) on Sat, Dec 16, 06 at 20:05
What minerals are benifical to Grevilleas.
Do they prefere an acidic soil.
Is it Phosphorus they do not like.
Is Phosphorus a chemical,why would it be in fertilizers,for what benefit.
What are the benefits of Nitrogen,if any, for Natives.
I have changed from,Sugar Cane Mulch to Lucerne Hay,(it is easier to get) can I mulch Natives with Lucerne.
Thanks for your time and I hope some answers.
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Follow-Up Postings:
RE: Nutrients for Australian Natives
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- Posted by roysta Gosford NSW (My Page) on
Sun, Dec 17, 06 at 10:00
| Of course you can mulch natives with lucerne, works just like sugar cane. |
RE: Nutrients for Australian Natives
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| g'day nemo, i think it is the phosphorus that the natives aren't happy with? but as for nitrogen and trace elements there should be no problems as there will be no problem mulching with lucern hay if that is what is easiest for you to get. len |
Here is a link that might be useful: len's garden page
RE: Nutrients for Australian Natives
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- Posted by pos02 NSW Aust (My Page) on
Sun, Dec 17, 06 at 19:50
| Very basically, like all matter on earth, phosphorus is a chemical (as are you and I). It occurs in most soils throughout the world, and the local plants use it to their advantage. In most Australian soils, phosphorus is deficient, and so the plants (eg proteacea) have developed systems to extract as much as they can (which is why adding phosphorus to the soil will kill them). You can use proprietry fertilisers which are low in phosphorus for native plants, or you can just use compost. This should be enough to keep them healthy - after all they survive in our conditions with no help in the wild! |
RE: Nutrients for Australian Natives
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| N and P are part of the proteins and other biochemicals that form plant tissue, e.g. the leaves and bark. Hence all plants require both of these to be present in the soil as phospahtes and nitrates. Except for members of the Fabacaea plant family (legumes or peas) that have special root nodules containing bacteria from the genus Rhizobium. These bacteria are able to convert nitrogen in the air to nitrates that are then absorbed by the host plant. Another exception are the carnivorous plants that obtain their nitrogen by trapping and digesting insects. In both cases these plants can grow in very poor soils, with little or no nitrates, where few other plants can survive. As for fertilisers, I find blood & bone to be an excellent fertilizer for a wide range of native plants, including the phosphorous sensitive ones. It breaks down in the soil slowly releasing small amounts of N and P in the same way as the slow release fertilsers like Osmocote do. It is also a recycled material and is quite a bit cheaper than Osmocote. |
RE: Nutrients for Australian Natives
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All plants need the three basics - Phosphorus, nitrogen, and potassium - to grow.
Artificial Phosphorus (as in superphosphate) was the fertiliser that revolutionised Australian agriculture, and is part of the reason why you and I live in a rather wealthy nation. It enabled crops which evolved in phosphorus-rich soils to be grown in Australia's old, low-phosphorus soils.
Not all Australian soils are phosphorus deficient. Rainforest soils have plenty of it, (derived naturally from the breakdown of plant materials) so rainforest plants are perfectly happy with ordinary fertiliser containing phosphorus. Plants which naturally grow on phosphorus deficient soils such as sandy heaths are happier without. Many members of the Proteaceae family (famously grevilleas, banksias, and hakeas) have evolved on phosphorus deficient soils so have evolved special root structures to wring the maximum phosphorus out of what they've got. Given it in an easy to digest form they overdose and die of "phosphorus poisoning".
Nitrogen stimulates green leafy growth, which can result in fast overall plant growth as it is the leaves that make the plant's food by photosynthesis, so the more leaves you've got, the more equipment for making food. It gives new little plants a kick-start in life.
Too much nitrogen makes weak plants which are entirely too yummy to plant-eating pests. Too little, and the plants stand still and look back at you from the same height for years. For trees and shrubs, though, it's probably unnecessary to fertilise anything after the first year.
Natives, in theory, don't need fertiliser at all. After all, they've evolved in this soil, so it should provide all their needs. However in practice the plants we call "natives" are often not really native to our patch, but grow in some other part of Australia so are, strictly speaking, just as "introduced" as roses and wheat. Fertiliser can help make up the difference between your soil and their original environment - if it's a richer one. In practice we are a bit inclined to grow plants from places which actually have very poor soil, so adding fertiliser is digging dollars into the garden. Often the illusion of a kick-start from fertiliser is actually caused by the careful watering that goes with it.
Plants which don't like nitrogen for similar reasons to those which don't like phosphorus (special root modifications) are, as Greg says, the Fabaceae (peas). They also include the closely related Caesalpinaceae (Sennas and Cassias) and Mimosaceae (wattles). You can tell this group of plants by their seed-pods which are like beans, usually long and narrow with the seeds all lined up, and made to open down both sides.
Casuarinas are extremely efficient plants which don't like either nitrogen or phosphorus added to their soil.
I don't know about Grevillea pH. It never seems to get a mention, does it? I suspect there's a bit of variation according to place of origin, (just as I suspect that rainforest species of Grevillea, of which there aren't very many, are probably perfectly unworried by phosphorus in their fertiliser). The prettiest Grevilleas seem to grow in gardens all over the place, so presumably they are not too picky about the level of soil acidity.
Original environment also gives the clue about how to apply mulch. Plants from environments with a natural layer of leaf-litter love mulch, and a nitrogen-rich mulch like lucerne is one of the best. This is because the process of breaking down plant matter uses up nitrogen at first, though it gives it back later. Putting mulch on the soil can actually result in nitrogen deficiency, and slow down the growth of small plants, or even starve them to death. High-nitrogen mulch - or some chooky-poo under it - solves that problem.
Plants from drier areas where leaf litter doesn't accumulate may turn up their toes with root-fungus - or just fail to thrive - if mulched, so don't fall for the "natives love mulch" line. Some do. Some don't.
Cheers, Trish |
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