Seeing as (at the time of writing) we’ve just launched our new gardening category in the Community forum, I thought there might be a few green thumbs out there keen to show off their gardening prowess. Even if you’re more like me (enthusiastic but perhaps not the most talented gardener), I’m sure we’d all still enjoy to see your favourite plant, favourite spot in the garden or any garden projects you’re working on.
To kick us off, here’s a pic taken a while back of the CHOICE veggie garden - a small garden maintained by staff just outside our office:
The patch looks a little tired. The herbs can be temporarily potted with exception of the rosemary which can be struck easily using cuttings. When struck, the old plant can be removed and the soil in the bed improved with some well aged compost and gypsum…both well dug in to ensure well incorporated.
The bed either is in a semi -shaded location or has poor drainage. If semi shaded, select veges which handle such conditions or if overhanging trees are the offenders, prune them back to let in more light.
If the bed is poorly drained, the incorporation of compost and gypsum will help (assuming the bed can drain) as well as moulding the beds so they are about 100mm higher than the edging.
Replant herbs/struck rosemary, with the rosemary placed at the far south to ensure it doesn’t shade other plants too much. Could also plant basil in the beds south in spring to complement the rosemary. Mulch with a finer mulch (sugarcane, chaff, pea/lucerne straw) and regularly fertilise with either organic/chemical fertiliser. With herbs or green veges, small fertiliser often is better than big less frequent applications.
If drainage is an issue, water only when required, rather than routinely (e.g. on a timer).
As the bed is small grow veges that need less space like Asian chives, smaller brassicas (e.g. tatsoi, mixuna), French (bush)beans, raddish, beetroot, carrots etc.
With old beds, the soil becomes compacted and can easily become compacted again soon after working. The gypsum helps with maintaining the soil structure to keep the soil open and well structured long after any compost has decomposed and disappeared. Being mainly a herb type garden at work, it is unlikely to be worked as much as a home garden making the gypsum addition even more important.
Gypsum should also be incorporated and mixed into the soil. With herb gardens, this can only be done when the beds are refreshed.
While gypsum won’t change the soil pH, it will add plant available calcium and sulphur over time.
I have not heard that before. Unless the soil is high in clay I cannot see how adding gypsum would do any more than adding organic matter and turning. Do you know the mechanism for this happening in non-clay soils?
Gypsum (calcium sulfate) adds calcium which avoids blossom end rot in tomatoes, pumpkins, zucchinis. A perennial problem in my patch. Calcium deficiencies can be caused by overwatering (diluting available calcium), or by high nitrogen reducing the uptake or by pH being too high or too low - again reducing uptake, just simply a lack of calcium in the soil.
There is not a lot to go on from just a single photo. Does the soil hold or repel moisture, are there lots of worms, is it easy to insert a trowel or fork, is the soil heavy or friable? So many questions, and many more that may or may not help.
Virtually all soils contain clay and silt sized fraction, unless one is one of a small number of properties in Australia build on sand dunes.
The covalency and size of the calcium ion in solution, as well as that most soil particles have negative surfaces, allows the calcium ion at sufficient concentrations to bring together the soil particles improving the soil’s structure. Calcium at sufficient concentrations can also overcome the dispersive effects of large and weak valency sodium ions. This is why calcium is an ameliorant often used on sodic soils.
Mechanical energy applies through the working of the soil can easily breakdown the weak bonds that cause the soil particles to aggregate. Gypsum has the effect of reversing the effects of the mechanic energy. The loss of soil structure causes greater settling and compaction of the soil over time. They are called pans or hardpans and can occur naturally or though poor soil management.
Most vegetable patch soils are overworked causing breakdown of the soil structure (unless one uses a zero till gardening method and doesn’t use any additives to the soil - fertiliser, tap water etc). Gypsum can help correct this loss of soil structure.
As also indicated, gypsum adds calcium ions and sulphates to the soil. In most vegetable gardens, the plants grown take up these and other nutrients causing deficiencies to occur, along with regular watering which leaches soluble ions from the plant root zone. Gypsum can help overcome calcium and sulphur deficiencies.
Thought I’d share my small garden and some of the plant growth that is happening in my backyard.
The only thing edible I can eat from my garden are these citrus fruits called, Calamansi (also known as Calamondin). They are basically a smaller version of a lime and lemon! But I am also propagating some other plant babies. It’s not the most impressive garden, but I am having fun!
It does. with our undergraduate students in soils physics, we used to do a simple test to show the effect of gypsum on soils containing clay and silt sized fractions. It is something one can do at home as well using two clear PET bottles with lids. Fill both with deionised water until there are about 50mm from the top. In one bottle, add a small quantity of gypsum (about 1/2 teaspoon more or less). Shake this bottle until the gypsum has fully dissolved. Then add a couple of tablespoons of soil into each of the bottles and shake vigorously (this simulates mechanical energy put into the soil). Leave and watch what happens. This simple experiment shows the effect on any soil containing clay and silt sized fractions (even those which are loamy sands and have a low silt/clay percentages of less than 20-30%). As indicated in an earlier post, the only soil which gypsum won’t have any significant effect is sands. This chart gives an indication of the soil texture classes and the percentages of each sized fraction in the corresponding soil texture class.
This website also provides some more information which you may find useful:
Assuming that the soil in the Choice office garden is natural soil…or is underlain by natural soils…using the NSW Geocortex soil mapping viewer, where the Choice office is located at Marrickville, the soil has been mapped as a Sodosols. These soils have a high exchangeable sodium percentage and respond well to the application of gypsum.
but that doesn’t mean the clay particles are clumping and will benefit from the application of gypsum.
I am sorry but you have not provided any evidence for that. I am not saying gypsum has no effect, it does do many of the things that you have described. I think you are making two errors;
saying that by looking at one image that shows little detail that drainage is a problem and that gypsum will fix it,
over generalising about the use of gypsum and its applicability to adjusting soil texture, gypsum is useful for improving the texture of high clay soils but that doesn’t mean that all soils containing any amount of clay will benefit from gypsum.
Before doing any soil amendment to a garden plot I would first investigate its composition hands-on. Regarding friability try the sausage test. Take a handful of soil and make it moist adding small amounts of water working it into a firm mud in your hands. Then roll it out on a hard surface or between your hands and watch how the ‘sausage’ of mud develops. There are youtube videos etc to show this in detail. If it:
crumbles and will not form a roll there is little or no clay,
will form a roll but not a very long one there is moderate clay,
forms a coherent sausage that can be bent and twisted without breaking, high clay,
is highly adhesive and can be made into any shape without breaking, use it for modelling or making bricks not growing plants as it is all or nearly all clay.
If your soil is in the low clay categories adding gypsum will do nothing useful to its texture. One should not add soil amendments without due consideration as some have side effects. For example gypsum can contain cadmium which with excess application could build up to harmful levels.
The garden bed is at near ground level and surrounded by concrete, either in edging and pathways. This will significant impact on drainage. As the underlying soils is also a sodosol, the underlying soil will also benefit from gypsum application.
Gypsum improves the structure in a wide range of soil texture classes including clay soils through to loamy sands. The benefits in lighter texture soils is that it improves aggregation of finer sized soil fraction, improving aggregation of these particles improving hydraulic conductivities and porosity of soils. The benefits are greatest where soils are dispersive (from being overworked, application of salts through water or fertilisers [both organic and inorganic] as often occurs in a vege garden or when the underlying soil is, such as sodosols).
I wouldn’t be relying on Youtube videos. I would rather rely on my education and early career as a academic in the field…principally looking at effect of mechanical breakdown of soil due to high tillage energies, such as those used in rice production to puddle the water on the soil surface.
While this is a generalised statement and isn’t correct. Soils can be light in texture and crumble easily as sand or larger sized soil particles dominate the soil matrix. They also contain significant percentages of clays/silt sized factions…refer to the texture triangle in the previous post. The only soils that contain very low levels or clay/silts are sands which are predominate along the coastline principally as beaches and dune systems, and in some alluvial environments where sand has been washed and deposited as predominately sand sized fractions (e.g. sand banks in creeks).
Even sand deposits extracted in sand pits contain clay and silts which are washed to remove these fractions so that that the sands can be used in the construction industry.
There are (high clay) Ferrisols in Australia that have a strong structure and due to the pedology, very much feel like a light textured soil and in the hand can fell like such. They won’t initially form a ‘sausage’ (will break apart as though the soil is high in coarse particles) until sufficient energy has been applied to the soil to breakdown the strong bonds within the soil. These soils have very high clay contents >80%.
This is sort of incorrect…it won’t change the texture unless added at quantities where it becomes a dominant soil component…it will change soil structure and its stability. There are many published papers from around the world on the benefits of adding gypsum to light textured soils. This is one of thousands published by the CSIRO:
Note: red earths are a sandy or light textures topsoil overlaying a clay subsoil. Cultivation of the soil in this article is of the light textured topsoil or A-horizon, and the subject of discussion.
There are also generalised statements made on TV garden shows or in magazines which are oversimplifications causing a misrepresentation of the full science behind the statements being made…examples are ‘don’t give natives phosphorus as it will kill them’…and looks liie gypsum use could be a misrepresentation of the science as well.
So you have said several times but I still don’t see the evidence.
That mention was not evidence of anything but access to another explanation for the way to conduct the test. The test was offered as a quick and easy method of assessing your soil friability with no cost or equipment not an academic treatise on soil science.
It appears you have a strong interest in the subject, which is good to see…not many others show the same enthusiasm or quest for knowledge on soils which is refreshing. Rather than providing a lecture on the subject of soil physics, I suggest you contact the Australian Soil Science Society Inc. to enquire about the soils short courses they run. While I haven’t been involved in them, the one introducing soils may be of interest. These are run from time to time around Australia for people/professionals who wish to know more about soils.
Disclosure: I am a member of ASSSI, but have no financial interest in these workshops.
Citizen Science: Living Soils, Growing Food (University of Dundee)
Not sure if they are still running. The Citizen Science ran an experiment; mono-culutre vs poly-culture, growing 4? crops to see if there were increases in production from one or the other. Along with soil testing & theory etc.
Here’s some photos of the basil in my garden. I was trying to photograph the bees. I’ll post some more photos of the garden tomorrow. The raised bed contains basil, garlic chives, parsley, capsicums, coriander and a Fijian vegetable called beley. The dark green behind is a choko vine on the fence. The chokos are fruiting now & off the one vine we are picking dozens, 5 or 6 a day.
Folks here who are interested in gardening might like to check out growstuff.org, a locally-developed project for gardeners to develop a dataset of garden info, keep records and swap seeds (where appropriate).
Gosh that looks like my garden! I let the lemon scented basil go crazy for ground cover, the bees and the added bonus that touching it makes weeding a fragrant delight.
Choko - I have planted many sprouted chokos without success. They either just die with a small sprout, or do a spindly vine and then die. No idea what I am doing wrong. They are in compost rich soil in the sub tropics, no frost. Maybe it is too warm? I planted two and only one is growing, but very slowly. I have about 3 leaves so far.