Soil Tips

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  • Does your soil have good drainage? Here’s a simple test:

             Dig a hole about 30cm deep and fill it with water. When it has emptied, fill it again and time how long it takes to empty again.

             Less than 1 hour indicates very good drainage

             1-2 hours indicates good drainage

             2-3 hours indicates fair drainage

             3-4.5 hours indicates poor drainage

             If it takes more than 6 hours it is probably not suitable for planting trees.  Ref:  RFC Brisbane Branch newsletter Dec 2001 N/L

  • Jude Lai showed us a technique that his father in China had used in the preparation of earth for planting. A fire was made using large logs and other wood, then soil mixed with grass was added on top of the still burning wood. This heap continued to slow combust for weeks, depending on the amount and size of the logs. The resulting “Burnt soil” had a really good structure and contained a lot of charcoal and carbon, with the addition of some manures/compost this makes exceptionally fertile soil.  Ref:  RFC Brisbane Branch newsletter June 2001
  • Don Ellison says that by using weedmat he bought from Bunnings (not the commercial type you get elsewhere) that his passionfruit vines grew three times as fast as those without. The mat is about a metre wide so cut off a square and slash it in a cross in the centre. It stops water evaporating and heats up in winter.  The reason he prefers the Bunnings type is that it is more open.
  • In a recent edition of The Weekly Times there was an article on huge variations in soil test results for phosphorous from three different laboratories which has prompted Australia’s industry watchdog to act. Apparently one of the Landcare Offices found Olsen P results from three soil testing labs in Victoria and South Australia delivered results which varied by 250% yet all three labs are listed as being proficient at testing for Olsen P with the Australian Soil and Plant Analysis Council. They believe it was the methodology used as results should not vary by more than + or – 20%. ASPAC certifies labs as proficient by sending each of them three batches of four soil samples over 12 months. However, the tests are not blind with each lab knowing the sample is part of the ASPAC proficiency test. Consequently some industry commentators say there is a real risk of labs putting their best lab technicians on to test the ASPAC samples and repeat them if they think the results are not right.  Ref: STFC newsletter Oct Nov 2009 – Sheryl Backhouse
  • Have you got that hardpan soil that sets as hard as concrete so that if you threw a crowbar at it, it would bounce back? Bill & Judy Winters decided to plant mangoes at Kununurra WA a few years ago. After digging the hole he added mulch, earthworms and a few seeds of the fast growing tropical leguminous tree called Verano stylo. Bill also placed a hard flat rock beside the tree to provide a cool moist microclimate. The Verano fixed nitrogen, gave shade and dropped fibrous nutrient rich leaves to add a layer of mulch. The Mangoes did exceptionally well and irrigated from gravity fed pipe but this was turned off after six years. Mulch is put on once a year and animal manure sourced locally. Kununurra has a reliable wet season followed by a long dry season so is perfect for Mangoes.
  • Growing in Swampy Conditions compiled by Sheryl   One of our members has this type of soil and is having trouble growing fruit trees. I asked Peter Young from Birdwood Nursery about it and he said:  “Mango roots have the ability to grow in anaerobic conditions. The most amazing thing I saw in the Everglades in Florida were mango orchards growing on flood plains and for four months of the year, the water comes up the stem and the trees are happy and they actually pick the fruit in boats. Around the water line, the mangoes have developed little pores through which the tree breathes and one of the researchers was trying to work this out so he took some Vaseline and put them over all the little holes and within 24 hours the tree died because it couldn’t breathe.” I put it to the rarefruit group and Zig from the Northern Territory said: “Some mangoes here are flooded during the wet season and seem to do well. My place has a swamp running through it coming from my neighbour’s property on the other side of the road (east). He’s planted mangoes into the swamp and they spend a few months in flowing water. The swamp completely dries during the dry season. During mango fruiting there hasn’t usually been enough rain to even make the swamp waterlogged. Fruit picking is done from a dry ground surface. I’ve never noticed any significant difference between his seasonally flooded trees and the others on higher ground. I’ve a few mangoes in waterlogged ground on the edge of the swamp as well as a couple of cashews. It doesn’t seem to have disadvantaged them in any way.There are other areas of inundated mangoes here as well and there’s a belief among some that this stressing of the trees causes early flowering. There’s a few months gap between end of flooding and start of flowering. A lot of tropical trees in monsoonal climates are adapted to dealing with water logging for part of the year. Apparently high oxygen levels in rain water are sufficient for them during the flooding, and oxygen is drawn into the ground as water recedes during the dry season.”
  • Sheryl   The interesting thing about this is that I have planted a whole hill of different Mangos with no irrigation at all. They get an initial bucket of water when planted and that has been all I have had to do so it looks as though they can withstand both wet and dry conditions.
  • Soil Testing by David Stewart DPI Samll Land Information   email:   Ph: 0419 116 759
    A soil test is only as good as the sample and the recent rain has created ideal conditions for soil tests. The soil is moist and the sampling can be done to the correct depth. Samples should be taken to a depth of 10cm which will give you a good representation of your topsoil. A shallower sample may give you an optimistic result because it will contain more nutrients and organic matter, whereas a deeper core may include a greater proportion of less fertile subsoil. A poorly sampled paddock can lead to misleading results for soil nutrients and incorrect expensive decisions on fertilisers. Take at least 30 samples if it is a large area you want tested to get an indicative sample of the paddock. Sampling diagonally at fixed intervals across a paddock will allow you to repeat and compare samples in future years. Avoid samples from areas around troughs and cow pats as these can also give a misleading result