Mid North Coast Microherders

Caring for the little things in our soils

Kempsey Landcare David Hardwick Workshop 3 July 2015 Part 1


Soil is my property's most important asset? Soil. What level and condition do I need to keep that asset in? How quickly would I fix a problem with it? Prioritizing. If soils are really important to us we put priority on maintaining it. What can we do to maintain that asset? [How many wheels do we want to keep on a ute to maintain it? 6!] When it comes to soil it is about starting to ask yourself what is the minimum structure, minimum ph, minimum organic matter, minimum aluminium,... for the soil to be in working order? It's about thinking that through and saying “I need 2% or 4% and making sure that happens.” How much fuel does this car need to go? How much fertiliser does my soil need to grow crops? How do I assess the soil? How do I check that it is in good condition? Ph meter; salinity meter; look at the roots on the plants;,,, In your vehicle you don't need to be a mechanic, but you need to check the gauges on the fuel tank, oil. Noises, water,... Same with the soil.

Did you bring a soil sample?

Natasha – Landcare Officer.

Riverina Soil Consultant – David Hardwick

Ways to identify good soil: colour; holding together in structure; moist; ….

People have brought soil samples. We have to go over at morning tea and score them and put a mark on the 'Best Soil in Show' for the day and there'll be a prize! (Jeremy not allowed to be in the competition because he is in Landcare!)


Role-play game. Brainless bacteria.

Protozoa – naked amoeba – I eat bacteria fungi. Mite – I eat nematodes.

Plant comes up. Grows roots. Grows taller. Photosynthesizing. Needs water, CO2, O2, nutrients, sunlight. CO2 is a very small amount in the air, but despite the very small amount, all the greenery on the earth is being created. The plant fixes CO2 and makes organic matter (carbon) – sugars in plants. [Minties]. Some carbon goes down to the roots, and some goes to building the stem and leaves, and some goes into the soil in a process called 'dribbling' – exudation. While it is green and growing, every plant gives out some of its carbon to the soil through the dribbling process. You can see it is the topsoil – rhizosphere. It is under the influence of plants. Then everyone comes around to eat it in the rhizosphere.

The plant needs nutrients from the soil: nitrogen, potassium, phosphorus, sulphur, calcium, trace elements.

Most of the nitrogen in a paddock is in the air (78%). Is it easy for the plant to get the nitrogen? No – it needs complementary ways to get it out of the air. Rain in storms, lightning brings lightnings down into the soil. Nitrogen fixing plants. How does the nitrogen get out of the air into the soil? There are bacteria that can help get the nitrogen out of the air into the soil. Nitrogen-fixing rhizobia bacteria. [When you buy legume seed you have to buy innoculant bacteria with it, otherwise the legumes will use soil nitrogen to grow!!!]They live in the plant roots. The bacteria like living in the plant roots because they like 'Minties' – sweet food from the plant. Carbohydrates created by the plant creating organic matter photosynthezing. The bacteria have worked out how to fix nitrogen out of the air and bind it in its body avaoaboe for use (choccies). They are doing a swap of minties and choccies! The nitrogen in the air was in the form of di-nitrogen; a very strong bond. Lightning breaks the bond, or fertiliser factories which use a lot of energy to break the bond. The bacteria break the bond but they need energy to break the bond, and they get it from the plant. It is a symbiotic relationship. The bacteria live in nodules on the plant root.

The air has to glow through the soil to get to the nodules, so if you have soil compaction you are already behind the 8-ball because the nitrogen can't get to the nodules and bacteria. Also if your soil is waterlogged.

The relationship is only with legumes (between nitrogen and plants)

Phosphorus (blue lollies) is also needed. Most of the phosphorus is in the rocks – in the minerals from the rocks as the rocks break down. It is locked up is a form that is bound to the parent rock part of the soil. Not very soluable. Unavailable. Insoluable. A little bit of phosphorus is in the plant material. Av ery small proportion of the phosphorus is soluable and is in the soil. It all depends on what type of minerals you've got how much is available.

Fungi and bacteria, acids on the plant roots can unlock the phosphorus and make it bioavailable (red lollies). The fungi that does this lives on the plant roots. It gets energy (Minties) from the plant roots. The fungi's hyphae are o;ut in the soil. They are able to crack the rock and release the phosphorus and take it us. They use an acid to do it. Superphosphate is made by treating rock phosphate with sulphuric acid. The fungi and the plant roots have a deal going where they swap Minities and red lollies. The fungi is vam or myccorhyzal fungi.

About 80-90% of plants have vam relationships with fungi.

There is another bacteria that is free-living (doesn't live in the plant roots) but also fixes nitrogen). It gets its energy from the dribbled Minties that plant has released into the soil. It is living in the rhizosphere.

There is another fungi that lives in the rhizosphere but not in the plant roots, and gets its energy from more complex woody stuff in the soil, and a bit of Minties, and they soluablize phosphorus. They are free-living. They depend on the dead organic matter that ends up in the soil (dead roots and leaves,...)

If dead leaves and organic mattter just kept building up the soil would go acid (a peat soil and eventually coal). However, this usually doesn't happen, because it gets decomposed. Decomposition is important to understand.

If we start with a compost heap a meter high, in three months time it will be half the height, because of loss of moisture, loss of CO2. As the fungi and bacteria decompose, they breathe out CO2 as everyting is eaten. What is being eaten is the organic matter.

Bacteria like really simple food (Minties). They don't have a brain or a digestive system! Red cordial will do. They also get a bit of phosphorus, calcium sulphur from the organic matter in the soil. As they eat the organic matter, they get energy, but they also get a bit of other nutrients. They live in the zone of the soil (rhizosphere) where there is a lot of minties. They decompose the organic matter from the plant.

You get an peat soil when decomposition doesn't happen except slowly – often coastal, waterlogged soil.

Protozoa eat bacteria and fungi. Bacteria and protozoa are microscopic. Protozoa are like cattle grazing on grass. There are millions of bacteria, and they get eaten. Then the protozoa poop out the stuff into the soil. Not all (they have to live) but most of what comes in is excreted out..

Some nematodes eat protozoa. Springtail nematodes eat fungi. Larger and larger organisms in the soil. They eat the smaller ones in the food chain, then excrete.

Nematodes are aquatic and live in the water film around the soil particles. Predators. Springtails are insects and they need air and good structure, and they et other things and as they eat they excrete. Mites eat nematodes; some eat mites and fungi. The benefit of the soil is that nutrients are cycling. Mites have 8 legs, and are related to spiders. Springtails have 6 legs and are related to insects.

Another thing that eats is worms, and termites. Termites are eating cellulose (dead roots etc) – it has almost no nitrogen in ti. Where do they get their protein? They grow fungi on the ground up wood and that helps them digest the carbon. They get their nitrogen from the air via symbiotic bacteria in their guts that are nitrogen-fixing bacteria.

We have manure, dung beetles, earthworms. Algae – a simple single-celled organism in the soil that do similar things to plants – photosynthesize and create carbohydrates.

Dead animals. Everything is getting eaten.

Some organisms like to eat living plant roots. Cockchafer. Army worms. Symphyter. Some nematodes. Phytophera.

There are some fungi that live in the plant roots that protect the living plants from being eaten by competitive exclusion. Bioprotection. If there is enough diversity in the soil then the numbers are kept in check by the other guys. If the soil is really simple then the plant living roots eaters have a ball.

Oyster mushrooms eat nematodes.

At that scale that we can't see with the naked eye there is a lot going on.

As the nutrients are excreted into the soil in a solluable form, the plant will take up some. Some will go into the air. Denitrifying bacteria. Other bacteria take the soluable ntirogen and phosphorus up . It tends to always tie up. Millions upon millions of bacteria. As long as the cycle keeps going it is ok. As long as it is the biological forms of the soil it won't volatilize into the air or wash down into the creek. It needs warmth, air, water, soil structure.

Now, let's toss some di-ammonious nitrate (urea)and phosphate on the soi. (Bought at the shop) So these are soluable nutrients. Bacteria eat some. The plant grabs some (about 30%). Some goes up in the air. If the plant was already getting enough nitrogen less would be taken up from the bought stuff. Hopefully the stuff nutrients that went into the bacteria will cycle over time, providing we have a soil that is cycling. It depends on how quickly we can stabilize the soil into cycling bacteria. If you don't have the bacteria and cycling soil then you have a low uptake of nitrogen by the plant – it is a hip-pocket thing. There is nothing wrong with shop-bought fertiliser, but if your sil won't take it up than it is a waste of money.

Have to get a more holistic understanding of my nutrient management.

Soil is a living thing. It is not a hydroponic growing media. It is a complex living thing. Don't throw the chemistry out, but also have to manage the living organisms.

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