Browse Forums Landscape & Garden Design 1 May 25, 2015 2:28 pm Need a little help with soil prep on clay slope.... I have read Fu's 28 pages of turf laying guidance (twice) and now have a grip on the basics I think ... But I am still not 100% on my way forward ... I live in the Hills district of Sydney, lots of slopey land and lots of clay !! Here is the front yard (and nature strip) we are trying to returf : Like ⋅ Add a comment ⋅ Pin to Ideaboard ⋅ Like ⋅ Add a comment ⋅ Pin to Ideaboard ⋅ Based on what we knew and advice given by landcapers, we went ahead and excavated the top layer of clay soil, old dead lawn (which we had roundup'd), and rubble from landscaping work (mess that the landscaper left behind in our front yard!). Excavator did some shaping of the land as well. Probably excavated 150mm, then paid a bucket load of money to have it disposed. So our top soil was essentially removed and we had a flat clay surface. Ordered in a bogey load of "80/20 turf underlay" and got the excavator guy to bobcat it around while hubby and I used rake and soil spreader to level it (about 100mm of soil). Was gong to turf it a week or so later, but life got in the way and we let it go a bit longer. Then the torrential rains came down on Sydney and washed all our work downhill That's when I came across Fu's great advice on turf prep, and what seemed like bad luck has turned out to be a blessing as we now have a chance to prep the soil properly before putting down turf. Here is where I have some Q's... 1. There is still a bit of the 80/20 underlay over the clay (mainly on the edges), so do we incorporate all that back in with the certified organic soil and count it as our now "existing soil" ? Or do I count this as my sand input for the 1:2 organic soil to sand ratio ? 2. I have contacted ANL Landscape supplies at Badgeries Creek and they have suggested I use something called Re-Build (NASSA certified), at $50/m3. It is a composted soil conditioner made up of green organics and forest residues. Is this the right product to use as my "certified organic soil" or do I need to add something to this ?? By the way, the very helpful chap at ANL emailed me the specs on this product if anyone would like it. 3. How much of this organic soil would I need for 300sqm (including nature strips) ? here is a close up of current soil levels : Like ⋅ Add a comment ⋅ Pin to Ideaboard ⋅ I am worried that I will need a boat load as I am not only trying to improve the clay, but also trying to raise the levels as we ignorantly disposed of our top soil/clay 4. We have decided to put off the turfing until warmer nights, so maybe late September. What can we do over winter to prep the soil ? Assuming I cant do much as I am on a slope and working the compacted clay will mean more soil erosion ? I would love to work something into the clay over the next few months to get it ripe and ready for the soil prep in Spring. I am madly trying to find the answers in the threads, so I do apologise if I have asked something that there is already an answer for. You guys are all an amazing pool of turfing knowledge and many have become great scholars and practitioners of the Fu way of turfing so I am sure someone out there will be able to help me. I am such a big fan of this new way of doing turf! Still trying to convince hubby though. We had the landscaper prep the backyard for us, and we laid 70sqm of SW, its a goat paddock that I would love to rip out and start over, but that's for another post Re: Preparing clay soil on slope for turf 2May 25, 2015 8:24 pm It's not turf, but something that may help bind your loose soil together until you can lay your turf down. Jap Millet seed. I spread that over the sloping sections of soil, watered it in, then it shot up fairly quickly. When you go to lay your new turf, mow it first, get some roundup on to it to kill it off, then lay the turf over the top of it after it has died off. Owner Building at Jimboomba Woods in Logan City Qld. Blog : http://bandlnewhomebuild.blogspot.com H1 thread : viewtopic.php?f=38&t=68283 . Re: Preparing clay soil on slope for turf 3May 26, 2015 10:19 am I would rather not plant anything only to have to kill it off, using more RoundUp ( we have used bucketloads to kill off the couch we had before) !! But you got me thinking outside the square ..thanks ....maybe incorporate a few garden areas and reduce the lawn area in that whole front and corner. Re: Preparing clay soil on slope for turf 4May 26, 2015 1:19 pm Ok not getting many responses...I think my post was just too long winded and too many questions. So just one question then - what do I do with the 80/20 underlay that's sitting on top of the clay. I am concerned about all the warnings of not to mix in sand with clay, or if needs be add a LOT of sand, not just a small amount, otherwise the clay will become like concrete. Do I: 1. scrape the 80/20 off so I can rip the clay underneath and add 100mm compost ? Then layer 100mm of sandy loam over it ? 2. dont scrape it, add a lot more sand and lots of organic compost and turn it all through the clay to 200mm or so ? 3. just layer more 80/20 over the clay (I will end up with about a 120mm layer) and roll out my SW turf on top ? Re: Preparing clay soil on slope for turf 5May 26, 2015 2:01 pm I'd do no. 2. There is nothing wrong with your 80/20 mix that some more organic matter and a good mix with a rotary hoe down as far as you can go will fix. That mix if I remember is already 80% sand so by mixing in some more organic stuff will just make it better all round - nutrients, water retention, drainage etc. If it means a bit of clay gets accidentally mixed in with it when you deep till the soil with the rotary hoe, that won't be a problem either. With the slope of your property drainage won't be a problem. If you aim for your top layer of mixed soil/sand/organic matter to be greater than 100mm preferably 150mm you should end up with a great looking lawn. As FuManchus article says, the better the prep the better your lawn will look. It should also require less water in summer and hold the water for longer. Stewie Re: Preparing clay soil on slope for turf 6May 26, 2015 2:49 pm Thank you SO much for your response stewie !! I really appreciate it, and just what I wanted to hear. Option 1 and 3 just didn't sit well me at all. So soil prep wise, is there really nothing much I can do until just before turfing in Spring? Assuming if I do disturb the current soil, I will just add to erosion issues. What about liquid compost (if there is such a thing) or something that I can just spike into the clay between now and Sept, so when I start digging in Sept, the soil is a little more workable ? Or I was thinking something like a thick layer of compost held down by a jute mesh ?? Or should I just sit tight and tackle it all in Spring ? Re: Preparing clay soil on slope for turf 7May 26, 2015 4:36 pm There is no reason you can't do some of the prep now. Maybe adding some gypsum or any other claybreaker to help loosen up the top layer of clay between now and spring ? I've seen some turf go down in winter so but I'm unsure whether it was Buffalo, Kikuyu or something else... If you are thinking of doing garden beds or planting shrubs maybe look at that in the interim. There can be a lot of work in those depending on how extensive you want to go. Stewie Re: Preparing clay soil on slope for turf 8May 26, 2015 11:41 pm Going to go the opposite than suggested.. I would do 1 then 3. Rip/dig up the existing clay to about 150-200mm then mix through a organic compost then put your 80/20 mix back and top up to the level you want. The clay you have left will be pretty horrible stuff as you had the top soil scraped off and removed. Takes years to make a clay subsoil a reasonable turf soil unless you like cricket pitch hardeness not to mention clay soils on slopes are very hard to irrigate due to water runoff. Ideally it would have been better to scrap off your top soil and store it to the side then dug out the clay sub soil and disposed of that then put your top soil back. Dem the breaks though. The 80/20 will do the job though, i wouldn't be bothered trying to make heavy clay into gold. It still will be rock hard in summer and slop in winter even with all Fu's soil prep.. Re: Preparing clay soil on slope for turf 9May 27, 2015 12:32 am So glad you turned up Beatrixkiddo, I was waiting for you ! Have gleaned some great tips from your previous posts. OK suppose we scrape up the 80/20 (or whats left of it) ...I expect there will still be residual 80/20 left on the clay as we wont be able to scrape it ALL off cleanly. Its all over the place as its been there since late Feb and has been through many a heavy rain (the silt fence only went up after all the heavy rain when we noticed we were literally throwing our money down the drain Will it be OK to mix the residual through with the clay subsoil and compost ? Can I expect any negative impact of the 80/20 mixing in with the clay ? Or as Stewie said, is it all good stuff as I am adding compost to the mix ? Hope I am making sense. Re: Preparing clay soil on slope for turf 10May 27, 2015 5:31 pm Yeah as Stewie said there is no issues if any of the 80/20 mixes with the clay. It would be hard for it not too Compost is a soil ammendment, so its not actual soil. Its job is to change the structure of the clay so it drains better and is more hospitable for plant growth. Compost does this in both clay and sandy soils so if mixes with the 80/20 dont worry. There are a threads where a few us talk about gypsum and dispersion tests if you want search and go further with your soil prep. Re: Preparing clay soil on slope for turf 11May 27, 2015 9:51 pm OK great, thanks. Yes I did the dispersion test with rainwater. The soil piece after 30 hours was not dissolved at all. So looks like not reactive to gypsum. I will be getting the soil Ph test kit from Bunnings this weekend. Re: Preparing clay soil on slope for turf 12May 29, 2015 12:09 am Since you will have the ph kit it wouldn't hurt to test your imported soil as well. Unless you buy your soil certified or to aust standards the landscape suppliers can sell soil with the ph at any level they want. A lot are good, a lot aren't as well. You get what you pay for generally.. Re: Preparing clay soil on slope for turf 14May 29, 2015 8:41 am Yep the 80/20. Good choice on compost. Re: Preparing clay soil on slope for turf 16May 29, 2015 6:15 pm Old mate Hi mightymo, Excuse my ignorance, but what is 80/20? thanks. Hi Old Mate, 80/20 is a washed sand and screened soil blend (80% sand) used as an underlay for new turf to help it to establish, or as a top dressing over the laid turf. The reasoning is that grasses generally grow better on sandy soils. However if layering the 80/20 on top of clay soil, it is best to prep the clay beforehand so that when the roots get to the clay layer, they are better able to penetrate and not develop shallow root systems to the depth of the sandy layer only. Also referred to as sandy loam. Re: Preparing clay soil on slope for turf 17Jun 05, 2015 1:11 pm Aha. Sandy loam. That is what you are going to need for your turf. You have a bit of a dilemma - you want to prep the soil now but don't want to turf until the ground is warmer. Btw, the ground will take quite a bit of warmer weather to warm up, I would suggest late October rather than September. OK, this is what I would suggest. Firstly, do some planning. Do you really want turf over all that area? Turf is fairly high cost and maintanence. Garden beds, properly established, are not (imo). Also, the land form - you have a pretty constant grade from your building to the verge, now is the time to look at shaping that if you would like a flat area around your house or a swale. (Look at your neighbours across the road.) Being a corner block you could have a couple of metres of flat off that driveway running around the corner, perhaps. Now is also the time to consider any other hardscaping you may want - paths, etc. You should consider a mowing strip between your house and letterbox and the turf, something to run the wheel of your mower on. Makes maintaining a neat lawn edge easier. Could use brick pavers or pour a concrete strip. Aside from that, your soil prep. Issues you have are an unstabilised embankment which will be prone to erosion and weed attack, and your clay soil which you would like to alter. Design and prep your garden beds and complete any hardscaping. You can plant out your garden beds now, use Fu's soil prepping and mulch with say 50 mm pea straw, 50mm tree mulch. Use a sandy loam to say 200mm, discard the excavated clay if you have to. Yes you can and should try to recover as much of the 80/20 as possible, use in the garden beds. Right, to your levels. Ideally, I believe you want the top of your soil in turfed areas to be about 20mm below your paving / mowing strip at turf establishment. That is the soil, not the leaf blade. This will let your paving drain to the lawn and allow for top dressing in the future. (Remember it is far easier to raise a low patch than drop a high one.) You need to then work back from here - go and see your turf rolls, measure how thick they are. Draw a profile of your paving with your clay , then draw the rolls on top, see how it fits. I would work on 200mm of topsoil, including turf, above the clay, so 220mm below paving level is top of clay. Do the earthworks for this. However, this is only at the interface with paving - you can "lose" the excess dirt into the middle of your area if it is not too much and does not create too much mounding. If you are going to reshape the slope then work from your paving edge inwards, establish the 220mm step all the way around first and move the dirt to your fill areas, after recovering and setting aside any topsoil (the 80/20 you can recover). When cutting back soil around your paving and building areas, dont undermine the concrete edge, step off it say 100mm or slope away from the bottom of concrete at a 1 (rise):1.5(run) grade. (You can deal with this dirt later when the turf rolls come in, just box it out then to slot the turf in.) That will leave you with your turf areas. As they are going to be fallow until spring, you need to combat erosion and weed attack over the winter. (Ironically, your turf is what would be doing this job for you.) To slow the velocity of water running over your slope, get it cross ripped or do it by hand. So create a series of trenches across the slope to try to get the water to penetrate. The more the better. "Lose" the spoil from the ripping. Then I would be respreading the topsoil and incorporating as much organic material as you can find cheaply. Grass clippings (same variety as your turf), raked leaves, straw (make sure it doesn't contain seed), anything fine you can mix with your topsoil. Chuck in some gypsum, can't hurt. Just cover over the rip trenches to get a uniform surface. Cover the entire area with a thick layer of tree mulch and walk on it to bind it together. Done. Pull out or spray any weeds over winter. Come spring, bring in your soil ammendments, organic soil and sandy loam (minimium 20% clay, it would be ironic to be built on clay and have non - wetting sand!) to bottom of turf rolls level and lay your turf. Either rake up the remaining tree mulch and re-use on your garden beds or just go straight over the top with your sand if it is thin. Expect your finished levels to drop a little as the organic mater becomes humus and everything compacts a little. Just top dress in very thin layers with 50% sandy loam 50% fine compost to lift it once the lawn has established if need be. My $0.02, hope it helps Re: Preparing clay soil on slope for turf 18Jun 05, 2015 5:54 pm Wow Old Mate , that is some super advice I really appreciate the time you took out to reply. I am reading each section and absorbing and trying to understand it. Will post up my plan forward when I have one. We are kicking off some work tomorrow morning to get gardens going and also a timber retaining wall that will extend the flat area beyond the driveway on the section on the other side of the corner. Will look into possibly extending the corner flat area around the corner as well, as you have suggested. Doing this as exempt development (ie. keeping it under 600mm high and atleast 900mm away from our boundary and other structures). We were going to do a lot of this our self, but I managed to track down a greenkeeper/horticulturalist/aspiring landscaper who was happy to help out for a bit of cash in his spare time Will start up another thread tonight to show our progress. I know how much I LOVE seeing progress photos and before/after photos on this forum, so will try to give some back. I've filled, levelled and compacted around 100mm of roadbase in preparation to lay some outdoor court tiles. Prior to doing the final compaction, I dusted the top with… 0 2606 I've dug some footings to embed a post anchor into. My holes are around 450mm deep which I'll put a 200mm stirrup into. The bottom of these holes seem firm enough. … 0 1547 A survey must’ve completed by a certified surveyor. This form part of every DA requirement 3 179532 |