What soil microbes actually do in your garden

You've bought the good fertiliser, you've watered it, you've done everything the packet said, and the garden still looks like it's going through the motions. Before you buy anything else, it's worth having a think about the soil itself, and specifically about the things living in it that you can't see.

Soil microbes are the bit of gardening nobody sells you, because there's not much profit in dirt that's already working. They matter more than most of what is on the shelf.

What they are

There are billions of microscopic organisms living in your soil. Bacteria, fungi, protozoa and plenty more. They break down organic matter, they cycle nutrients like nitrogen and phosphorus into forms a plant root can actually take up, and in doing so they build the crumbly structure that lets air and water move through the ground.

Without them you've got sand and clay with some chemistry sitting in it. With them you've got soil.

What they do for you

1. They make the nutrients available

This is the one that surprises people. A lot of what you spread on the garden is not in a form the plant can use yet, and it's the microbes that convert it. That's why the expensive plant food sometimes does nothing much. The nutrient was there and nothing was around to hand it over.

2. They keep disease down

A soil with a healthy microbial population is a crowded one, and the pathogens that cause root disease have a harder time getting established in it. Some beneficial microbes go further and actively suppress them. Bare, dead soil is where soil borne disease does its best work.

3. They hold water

Better structure means better water holding. Soil that microbes have been working on stays damp longer after a watering, which means less watering and more forgiveness on the day you forget. In a dry summer that difference is significant.

Four things that get them going

1. Go easy on the harsh stuff

Heavy chemical fertilisers and broad spectrum treatments give the plant a short burst and knock the soil life about at the same time. Organic and organic based fertilisers feed the plant and the microbes together, which is why the effect takes longer to show and lasts a lot longer once it does.

2. Add organic matter

Compost, aged manure, leaf litter. This is the food supply, and there is no substitute for it. A bag of compost dug through a bed does more for the soil biology than anything you can spray on top of it.

3. Keep the soil covered

Bare soil bakes, and the top few centimetres is where most of the microbial life lives. A layer of mulch, straw, bark or even your own lawn clippings keeps it cooler and damper, and it breaks down slowly into more food. Cover is the cheapest soil improvement there is.

4. Grow a variety, and move things around

Different plants push different compounds out through their roots and support different microbial communities. A bed that grows the same thing in the same spot every year narrows that right down. Rotating crops and mixing in flowers and herbs keeps it broad.

How long before you see it

Not next week. Soil works on a slower clock than we'd like, and you're looking at a season or two before the difference is obvious. What you'll notice first is that things hold on better through a hot spell, and that you're watering a bit less. The greener growth comes after that.

Shop related products

• Neutrog Go Go Juice 1L. A probiotic liquid that puts beneficial microbes straight into the root zone.
• Neutrog Popul8 1L. A concentrate aimed squarely at building up soil biology.
• Neutrog Seamungus 500g. Seaweed, fish and humic acid pellets, good for pots and small beds.
• Neutrog Whoflungdung Mulch 20kg. Composted mulch that feeds the soil while it covers it.

Did you know we also stock mushroom compost, garden compost with seaweed, lucerne mulch and mulch forks in the shop. Not all of it is listed online, so give us a ring on (08) 8536 4333 to check what's on the shelf.

Bags of compost and mulch are heavy, and we run a local delivery service on Tuesdays and Thursdays, $5 around Strathalbyn and $10 on the wider regional run.

The rest of the soil range is in the garden centre, and if you tell us what your soil is doing we'll point you at the right bag.

More from the garden

• How to make compost at home without it going wrong
• Neutrog Rapid Raiser, what it is and when to use it
• Crop rotation in a home vegetable garden, and why it works

You can read about soil biology for an hour, or you can come in and ask us and be spreading compost in ten minutes. Ask me in the shop, I'm usually there.

Cheers,
Candeece