Recommendations to fix bad soil

Thankfully, most of the steps you need to take to correct your soil's ph and other factors that affect soil condition are not expensive. In some cases, several bags of dolomite and some animal manure on a regular basis might be all you need to do. Recommendations are broken down below into specific situations (such as yellow clay soils, housing in new estates) and a large section on general recommendations which would apply to all situations.

For areas of yellow and grey clay:

Dolomite, dolomite and more dolomite! This is crushed magnesium limestone and is available in large bags and is cheap. Sprinkle everywhere at the rate of one cup (300ml) per sqm and water in. Do this treatment about once every 8 to 10 weeks but if you scored high in our questionaire, you can do this treatment monthly for the first few months. The dolomite will help shift the ph away from acid but also start to break up the clay a bit so that drainage improves and roots get more oxygen.

If you have a lot of acid loving plants (gardenias, azaleas, camelleas, rhododendrons, hydrangeas) or dry land natives (banksias, grevilleas, wattles, eucalypts) in part of the yard, you can use gypsum instead of the dolomite in those areas. The gypsum will help break up the clay but it does not shift the ph.

For areas of red clay:

This is volcanic in origin and drains better than the other clay colour types but it can still get acidic. If you have red clay soil but still scored fairly high on the questionaire (plants not growing properly; poor fruit production; too many recurring weeds), use the recommendations for yellow clay soils.

For sandy soils:

Drought tolerant soil fungi can be a problem in these soils but if you like in a flood zone, you also have issues of intrusion of soil problems from other areas when the flood waters recede.

Heavily mulch your garden beds with health mulch (fully composted) to increase the amount of moisture retaining material seeping into the soil.

Fertlise regularly with organic fertilisers - liquid products like Charlie Carp and Seosol can be used weekly; powdered products like blood and bone, 5-in-One and Triple Boost (made from earthworm castings, fish and kelp) can be used monthly.

For hillslope properties:

If you are on a slope that has not had any kind of terracing or retention walls added, you will have problems with the good things in the soil being carried away by the rainy season but also compaction of the soil and/or the erosion and loss of the soil itself. Less soil to hold in big trees means less soil structural integrity (risk of land slips/slides).

• The most comprehensive way to fix this problem is to build a series of retaining walls which hold in the soil and control where the runoff flows. However, this is a costly approach not available to everyone.
• Planting specific plants in beds going across the slopes will at least reduce the problem. Use legume species with fine roots (Acacias, poincianas, cassias supplemented by beans, peanuts, ground covers and shrubs with pea-flowers) will help hold in the soil and add nutrients.
• Mulch these beds with tea tree mulch or well composted recycled mulches (should have a pleasant "earthy" smell - if the mulch smells awful, its not composted properly yet).
• Use organic fertlisers and natural manures throughout the year but not just before or during the rainy season (they'll just get leached away so you'll be wasting money).
• Add more ground covers of the "green manure" type instead of lawn - you can use peanut, new guinea wingbean, or sweet potato which is allowed to trail on ground.
• Use the dolomite treatments (one cup per sqm) every 8 to 10 weeks and water in.

For new housing built on former (reclaimed) swamps or mangroves:

Soils in these areas aren't just acidic - they are acid sulphate (much worse)! Spread gypsum and water in for a few months and then start alternating with dolomite. Then switch to just dolomite after three or four months.

Houses in new/recently built subdivisions that were previously used for sugar cane or cattle grazing:

Long term use of nitrongen fertilizers can cause acid soil because the beneficial microbials (fungi, bacteria, yeasts) are killed off, plus these properties may have brought in unknown soil to fill in.

• Use the dolomite treatments monthly plus organic fertilisers/manures to condition the soil.
• You can speed up the process of leaching fertilizers and chemicals out of the soil but using epsom salts before starting your dolomite treatments. Water the ground first, then dissolve one cup of epsom salts into 5 litres of water and pourspray onto the pre-moistened soil.

For all soil types and terrain types:

• Avoid the use of herbicides if at all possible or at least heavily restrict their use. Herbicides influence the soil condition towards one which promotes the growth of weeds and they kill off some of the good fungi!
• Singapore Daisy is one of the most common and invasive weeds in the area but you can spray it with white cooking vinegar once a week in the early morning before the sun hits it. Lantana doesn't like this treatment either.
• Hand pulling by the roots is always the best way to get rid of weeds and this can be a family activity which helps nurture a planet-caring awareness in your kids.
• Sensitive weed / mimosa is a nitrogen fixer and you can kill it by overdosing it while fertilising your lawn with a high nitrogen fertiliser - HOWEVER, high nitrogen fertiliser will influence your ph so you need to be using the dolomite on the lawn as well. If you are using lots of superphosphate fertilizers and/or selective lawn herbicides, this pushes the soil towards acidic so use the dolomite about a week after each fertiliser/herbicide application to adjust the ph back

• For users of Biocycle and greywater systems – use dolomite monthly in the area where your outflow pipes drains out.
• When recent earthworks have occured (new driveway, pool, room extensions, brand new house, etc.) or if you have recently removed a significant amount of vegetation from the property, especially any big trees – use the monthly dolomite treatments if you scored highly on the questionaire or gypsum treatments if you had a very low score.
• Shade is important but some sunlight is needed: All living things need some sunlight to survive. If you have a very heavily shaded property, trimming back some branches on a few trees will allow more sunlight to reach the lawn and garden beds and this promotes the growth of some beneficial soil microbes - but don't get too carried away! Too much of a good thing is no good at all and shade is very important in the tropics. If the sunlight falls on exposed soil, fill in those patches with lawn seed, a "green manure" ground cover, or a new garden bed. Don't leave exposed soil exposed.
• Mulching garden beds is important for the soil and also to reduce moisture loss. But the wrong mulch can add new problems to the yard that could be difficult to fix (such as having to spray with fungicides). Tea tree and peanut mulches are good products but be careful when purchasing mulches produced from recycled garden scraps such as that which is distributed by councils. The mulch you select needs to be fully composted before you acquire it. A mulch that still smells "bad" hasn't finished the process of extreme heat buildup that a fully composted mulch has completed. This heat is so intense, it will kill weeds and bad pathogens. A mulch that hasn't completed the heating up stage will smell 'off' and will introduce a range of weed and plant disease problems to your yard.
• Mango trees - a tropical icon: Mango roots tend to influence soil condition but the leaves themselves go acidic after they fall off the tree and they very slowly break down. If you have a mango tree, rake up the leaves and either bag them up to put in the garbage bin for collection or rake them into a pile, sprinkle with lime or dolomite weekly and water in. The leaves can still break down in your yard but you'll be neutralising the acid they create.
• Food plants need to be fed: The more fruit trees and veggie gardens you have incorporated into your property, the more these plants need to be fed as they will be constantly taking up all the nutrients in the soil. Use organic fertlisers and manures regularly to keep the nutrients available for the plants and for the soil balance.
• Cats/dogs/aviaries/ducks/geese/chicken houses - The urine/faeces from these animals can affect soil ph as well. Worming agents used for cats, dogs and birds will be present in the animal's droppings and get into the soil. Use the dolomite treatments, esp. on particular spots where urine stains exist, to compensate for the effects their droppings have on the soil (this will also get rid of that urine smell)
• Insecticides used to kill roaches, fleas, mites, etc. are bad for the soil. Refrain from using them or use dolomite to compensate.

If you are looking for more information about caring for your soil and environmentally friendly gardening techniques, there are heaps of websites to visit. You can do searches using the keywords Weedbusters, permaculture, organic gardening, etc. and add geographic limiters so that you can find organisations in your own area.

Last updated: August 1st, 2009

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