The soil at Railway Parade

(…or, why I mulch and compost….)

Robbie over at Palm Rae Urban Potager made a great post about the importance of soils. With the 21st being ‘Save the Soils’ day, I thought I’d share a bit of info about what is under my feet.

To say that my soils are sandy and rocky is an understatement.

What passes for topsoil in much of Australia is in fact nothing more than ancient decomposed rock particles. This describes my yard: the soil is a mix of decomposed Sydney sandstone, Ironstone and a little bit of Granite.

The most surprising feature is that there is almost no organic matter: this is partly because the whole garden is on a steep slope and organic matter washes away in rain, but even in the lower parts of the garden, there is almost nothing. Despite this, the garden manages to house over a dozen very large, healthy trees (native and exotic).

But, as you can see from my humble attempts in this blog, even these impoverished soils support plant life. If it weren’t for the high rainfall in this area and the rock minerals present as a result of the decomposition of ancient stones, creating a garden in just sand and rubble would be seriously challenging.

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An area of ‘lawn’ (ie weeds: lawn is the last thing on my to-do list) and ‘topsoil’ in the garden, where is the organic matter (!?!)

Challenging alright…who has light beige coloured top soil?

Then there are the rocks…..any time I create garden beds, I dig, mattock and lever out vast amounts of them. These are just some of the piles in out-of-the-way parts of the garden:

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Some of the many rock piles pulled up while turning the ‘soil’

But these rock piles are slowly being re-used to create edging, raised beds and dry-stone retaining walls….

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Rock walls and edging

……and the little bits of rubble will be spread under pathways with a decorative gravel layer on top and it will be used to make Swales once I have finished terracing the site.

A great thing about these dry-stone walls is that they make fantastic insect-hotels – in fact they are the original insect hotels, long before the term was even invented! Pick up any of the stones and there all sorts of insects (both good and bad); lizards, spiders, centipedes, ants, woodlouse, etc using these as shelter and as their own supermarket…although in this supermarket, all the insects feast on each other.

Naturally I make my own compost, but obviously it’s no where near enough for a 1000m² (¼ acre) of garden.

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Latest batch is not quite ready – but at least it’s the correct colour (not beige like the rest of my ‘soil’)

There are of course positives to having this soil type: in addition to being very free-draining, sandy soils are easy to dig, don’t waterlog and because of all the rock nutrients, have fertility despite no organic content.

But it needs more organic matter, lots more.

Now as I can’t make enough compost (yet – each batch takes a few months) for the rate of new garden beds I am making, I have to bring in the next best thing – mulch.

I would mulch anyway to both conserve soil moisture as well as stopping run-off during heavy rain and protecting the soil from freezing in winter.

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I use Sugar Cane mulch which is a by-product of sugar processing (once upon a time it was just burnt). Sugar cane mulch contains Nitrogen, Phosphorus, Potassium, Calcium, Magnesium and Sulphur so actually adds nourishment as well as enriching the soil structure. The mulch breaks down quickly and doesn’t deplete Nitrogen from the soil like bark mulches can. Nor does it change the pH like pine-bark or pine needles. Here is an example of the soil after only 6 months of mulching with Sugar Cane:

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The good, well, slightly better, dirt….

Compare that with very first photo! Much more brown, much less beige – heck, there’s even a hint of black, just like soil should be!

I just need to add another 20cm/8″ of this sort of organic matter, as well as leaf mould (another reason why I have planted so many trees), before I have anywhere near what most people take for granted as the soil under their feet.

But at least it is much, much easier to fix a sandy soil than a clay one, so for that, I’m grateful! And there is one piece of advice that I learnt many years ago: “Feed the soil, not the plant“.

Happy Gardening and Happy Soil Day 🙂

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39 thoughts on “The soil at Railway Parade

  1. wow….you have a lot of work cut out for you! You are doing an amazing job!!!!
    I doubt you need to add rock dust-LOL…as I read your story that kept nagging at me—geez, he does not need rock dust!

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  2. We have very sandy soil here and our garden is not far from the Green Sand Ridge, dig down and its almost pure sand in places. Even though I have to work hard to add nutrients, I’d rather this than have heavy clay to work on. We have naturally high water table though as we are near a river. Interesting to see your results using Sugar cane residue.

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    • Absolutely – I’d much rather sand than clay. I don’t know of any other suitable substitute to sugar cane (apart from maybe pea straw) that works as quickly with as many trace nutrients. I’m reasonably lucky that Queensland is a major sugar cane producer, so it is only being transported one state; still, that represents almost 3000kms/1900mi away…

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  3. You’ve made impressive progress already Matt! I’ve whined about my rocky soil – our property was part of a large rock quarry in the 1940s before the land was sold for development – but I have nothing on you! I’ve used the pebble-sized rock in our soil to cover paths but would love to have your larger chunks of rock to work with (although I’m sure my husband is happy not to be on call to dig out rocks like those). Soil is also a big issue here – I make my own compost too but it’s not been enough so I’ve had to bring in truckloads of local topsoil.

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    • It’s challenging to work out what to do with all of the rock. Especially the little stuff…it’s often to large for a gravel path and too small for dry-stone work. The only use I have made of it is swales and fill on the larger retaining walls. I know what you mean about the compost…it’s hard to keep up with demand. Thankfully I haven’t had to get in any new soil (yet)

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  4. Matt, I am answering a question you had about the salvias I had in one of my posts. Its name is Salvia coccinea. It comes in red, white and pink. It will make it through a short freeze and it reseeds easily. It seems to like all kinds of soil.

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  5. I think my sand pile is worse than yours, The soil test made me laugh, it was so bad and mostly decomposed shell so a really Alkaline soil. I think clay is easier than this stuff, although I am constantly amazed at what you can grow in either medium.

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  6. I promise never to complain about my soil after seeing what you have to contend with. You’re doing a good job, though, and know what you need to keep doing to make it better. Gonna be a long process!

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  7. I’m impressed with your tenacity. Your hard work will pay off. When we bought our house 25 yrs.ago, the soil was gravelly. After all these years I have added maybe an inch of humus to the total. I could have gone more all out, but I used what I had to hand. It takes time, but is worth it!

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    • Thanks! Yes, just like you, I intend to use mostly what I have at hand and try and limit the amount of new material coming on site. After just 6 months, I’m impressed with the change in soil where it has been mulched, and terracing will help stop future organic matter loss, which means the leaf matter from all the trees on site will actually stay on site (rather than being washed away). It takes time, but it’s one of those processes that evolves…

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  8. Love your last phrase; “feed the soil not the plant” I agree wholeheartedly! My soil is similar to yours, a few less of the large rocks, mine’s all tuffo. I have been surprised how much it has improved since I’ve been adding mulch and compost and leaving flower petals on the ground, it is surprising that they are as good as leaves for improving the soil. Like you, I’d rather deal with the stony soil without organic matter than have to garden on clay even though that can have some advantages once it is planted.

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    • Yes, I always leave the flower petals where they fall, too. Your soil sounds very challenging, but it seems that the lighter soil is the easiest to improve (I have gardened on clay before it was more challenging than what I have now, particularly during wet spells)

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  9. Just found your blog through a share on Robbies Palm Rae Potager (awesome blog) and am going to follow it in my RSS Feed Reader. We live in northern Tasmania and have acid soil FULL of dolomite rocks that sit on top of a 2 foot thick band of massive sticky yellow clay. Give me sand any day! ;). The topsoil is just silt as we live near the river and we are, like you, on a steep slope that starts at the top of our 4 acre block sparcely populated by long suffering sheoaks in the Serendipity Farm equivalent of the Serengeti down to the bottom of the block, just over the road from the Tamar river which has tea trees on it (and thus showing how wet it gets down there in winter…swamp land!) I feel your soil pain and I also get your delight when it starts to develop. We use horse manure and oak leaves to get results here. Both are free and easy to get hold of so we get as much as we can and slather it about all over the place. Once we only had those huge big native worms but now we have all kinds of worms doing their thang. It’s amazing to be able to witness the transformation of soil. Glad to have found you and looking forward to seeing how you develop your own little patch 🙂

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    • Thanks! Tasmania is a beautiful spot indeed…..once I make a start on the other side of the paling fence that splits my property in two, then the lower section of that is actually a clay pan and is permanently boggy, but I’ve sought out some marginal swamp trees which in time will dry the ground, but of course the same principles will apply. Adding tons of organic matter and mixing it with the sandy soil from other parts of the garden. In lieu of proper compost, the sugar cane mulch really does encourage earthworm activity and is a god-send. If this had been 20 years ago, all I would have been able to use would have been pine park and maybe grass clippings!

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      • Sugarcane mulch is Australia wide now and we can get it through Bunnings here. I tend to use what is free and locally available (cheaper to drive and pick it up) which is horse manure in our local district and all of the oak leaves that I can rake in autumn from my elderly neighbours HUGE oak trees. She doesn’t want them and just burns them so if I rake like mad (and don’t fade from all that effort) I can get about 20 trailer loads of oak leaves that I heap up and mix through horse manure and that makes an awesome worm attractant. They can do some of the digging for us. Most of the time we just twitch whenever we have to dig a hole around here as it involves removing all of the rocks that said “hole” contains before being able to plant anything. I would much prefer straight clay to rocks over clay but you work with what you have. Are you only planting natives? There are lots of tree species that would love those kind of conditions in your new prospective garden area 🙂

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      • Burning leaves? You are kidding! I thought that practice stopped when I was young….I am putting in oak trees just so I can get the leaves. Of all the deciduous tress, these make the best leaf mould. They have also been shown to be fire retardant. I’ve put in a few natives, but only those that aren’t flammable, given that I am surrounded by almost 700,000 acres of tinderbox country. With natives, I am picking the cool-temperate rainforest remnants that are still around my area (which pre-date the thuggish Eucalyptus/Myrtaceae family): Northofagus, Cupressus, Araucaria, Atherosperma) The rest will be exotics chosen for wildlife…but in that new area, there will be a few river birches (the galahs – which get bullied out by the white cockatoo – love birch seeds and it’s too cold here for casuarinas)

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      • This elderly lady is 92. She mulches all around her oak trees but the problem is these oak trees are HUGE. They are situated on what was once the Auld Kirk church manse and have been there for 150 years. We know how valuable the oak leaf mould is and that’s why we rake and collect the leaves. Her husband (now dead) used to be the gardener. I guess her lack of excitement is our bonus :). You are right about the deciduous trees being fire retardant. None of the oils that our natives have or the desire to be burnt to propagate. Whatever you do, DON’T plant pitosporums if you are worried about fire. You should see them burn when they are thrown onto the fire. We burned some green branches. Thought that they would take ages to burn but they erupted in a fireball. Awesome to see and a timely reminder to get rid of them. You are speaking our language with conifers Matt. We both studied horticulture and specialised in conifers. Love them to bits, especially the Araucaria family. We found 3 Araucaria bidwillii seeds when we attended the Melbourne International garden and flower show back in 2009 and brought them back and grew them. Still have all 3 and are about to plant them out on the property. We have black cockatoos nesting on our back (bush/sheoak) block. They love the hakeas that someone had the presence of mind to plant here many years ago and spread them all over the place by carrying them and eating them in other spots. We have casuarina’s up the top of our steep block and Melaleucas (alternifolia) at the bottom. Arid at the top, swampy in winter at the bottom. Great to read about your plant choices. You know what you are doing 🙂

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      • Yes, I’ve watched pittosporum go off like a bomb. There are a couple of variegated ones on the block that are about 30 years old, and I haven’t made my mind up about those yet. I love the black cockatoos. It’s funny – here they eat cedrus, picea, abies and, at a pinch, Pinus radiata & patula pine cones (the white cockatoos also feast on pine cones). Moving here, surrounded by nothing but pristine bushland has been a real eye-opener….almost all the wildlife uses the garden exotics for shelter and food, which really has taken me by surprise.

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      • The black cockatoos love pines of all kinds. I guess hakeas might be one of their native foodstuffs? Conifers have much more dense foliage than natives so I guess they make excellent habitat (when they are big enough). Animals are pretty quick on the upbeat to take up residence in something new 😉

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  10. I am so sorry but just found your post this morning!!! Thank you so much for participating in Save the Soils Day! We are expecting a major blizzard (a record-breaker, from all reports) so it’s been a bit hectic. Will add a link to this on the blogger page. Re: your garden. I can see that everyone has their own particular challenges & you are tackling yours very well! Our yard is on an incline, too–which is great for duck pens but not as great for veggie beds. I’ve never seen a sugar cane bale but our straw bales work very well as planters and, after they do their job growing cabbages, whatever’s left is left in the beds for mulch. We love our deciduous trees for their year ’round beauty and, perhaps, esp. for their (hard-working) autumn leaves! Happy Belated Save the Soils Day! 😀

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  11. this might sound odd by I would love to have a rocky soil, as you say it is repairable, you are lucky to get the sugar cane mulch it sounds ideal, I am amazed your compost is ready in only a few months mine takes over a year, I would not like to garden with a mattock though, I like how you have used the stone, dark is not always good, I have a dark soil but as it is mostly peat it is nutrient poor, a soil without food and plants don’t grow, well done on all your hard work, Frances

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    • Thanks Frances…I have never had peat soils, except when I lived in London and I used it as potting mix, but the British swore by Peat based compost. I always thought it odd, as Peat was such a finite resource (I only found it marginally better than bark-based compost)…it reminds me of Australia’s fixation with coal-burning!
      The compost in winter takes quite a while, as I don’t have enough green material to add, and that area is quite shaded, but once the sun hits it and I’ve got lawn clippings to add, then it breaks down almost instantly

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