The Gordon Gnohm

Play along at home, read Future Farmer in The Braidwood Bugle every Wednesday. 

Bombay Spew – Sodic Soil

A wild start to summer! 200mm+ fell here in the first 24hrs and delivered 2-10mm a day, for 5 days after. 

When I first became custodian of my ‘rubbish block’, I naively thought it was because of the Kunzea dominated woodlands and total lack of pasture. It didn’t take long to realise what the locals in the pub were talking about. After a significant rain event the property would change. Areas of firm compact land became a floating balloon of earth, easily penetrated with a foot. I regularly lose a boot in the moosh, but only one, as the other foot is usually on firm ground. 

I have bogged many vehicles over the past 25 years from 8T trucks to 800kg hatchbacks. Never in the wild, only on proven driveway and building sites. The past few years have been so bad that I got a 4wd to access my property (but mainly to drive on our local council roads). I have bogged machines too many times to count, and my truck was famously bogged for 6 weeks last year. Its no way to run a business.

Colloquially known as Bombay Spew, digging is futile to impossible. How is it possible to be so hard when dry and liquid when wet?

Soil Structure

The soil varies, metre by metre across my property. There are multiple layers, roughly 600mm -1.5m deep before hitting granite outcroppings. Deeper in the valleys and shallow on the ridges of course. 

I initially thought there was no topsoil here, but I was wrong. The silty soil is eroded from the top of the hill by big rain events and held on the lower hill by the mass of Kunzea and native groundcovers. The Kunzea drops its tiny leaves into the silt and creates topsoil. 

The secondary layer is the white silty clay. This layer compacts easily and is evidenced in animal trails, wheel tracks and walking paths. It forms a crust over the property and holds back the liquid mud underneath in large rain events.

There are also smatterings of red clay, it is slippery and holds water but is easily eroded if exposed to the weather. The subsoil has rock fragments of varying sizes in it, then the bedrock. I understand there is a lot to learn and I’m no geologist, so I attended a local event and someone suggested it was difficult to work the Sodic Soils on my property. I had not heard the term before.

Traditional Management

Dr Google tells me Sodic Soil is full of salt. This salt is bound up in the chemical structure of the clay and reduces plants ability to thrive. Popular Science tells us to apply salt (super phosphate, lime, gypsum etc) to create a chemical reaction that converts the bound up salt in the soil, into water soluble salt. The salt in solution is then mobilised, and leeched out of the soil in rain events, or heavy irrigation. I’m not yet sure how this benefits the structure of the soil, more learning is required.

However, Logic suggests that this practice is causing salinity issues for people downhill, or maybe on your own property, where the salty water sits and pools. Harrowing more salt into this fragile soil structure will surely result in faster erosion, would it not? 

There are other ways to deal with the excess salt in the soil structure, as demonstrated by Mother Nature. A less popular scientific approach, and my number one solution to any soil problem is to add more organic matter on top. Regardless of your soil structure or what popular science suggests, just add more organic matter and make your landscape more like Monga NP. 

Baptism of Liquid Mud

The bogs occur where the water sits and pools, its simple to avoid these spots but that’s not where I get bogged. The pooling creates waterways underground that pop up somewhere else. One early incident involved machine work to create a turning circle. It was dry work on a dry day. What could go wrong? 

After clearing and shaping 50m of roundabout, a final drive over in the 8T tip truck to celebrate our work. This little mistake happened late on a Sunday afternoon. Bogged up to its axles without warning. It seemed like there was no risk at all, but the surface work had changed something, and the water was now flowing under the road from an event the week before. 

Digging created more liquid mud and bogged the truck further. A distant neighbour was called on to pull us out of the bog under lights. This experience led to the now common practice of leave it in the hole until it dries out, then drive it out, no fuss.

Management

The first step after Big Rain, is to restrict movement of vehicles and humans around the property. Generally waiting for water to stop running, sometimes days, but its better than getting bogged. Humans walking on proven tracks to achieve basic homestead tasks is the limit, but footwear can still be lost. 

The second thing is to add organic matter to the top of the soil. Do not dig it in. The microbes, worms and insects will do that for you if you give them a chance. Organic matter holds water well and the microbes create larger particles of soil to create structure and stability.

Third, appreciate the majesty of the mineral rich subsoil under all the organic matter. What is put on top will eventually be mined and deposited throughout the soil profile to create a better, deeper structure. Leaving the fragile soil structure intact for the microbes to improve is a lot more productive than pulverising all your earth and starting to build from scratch. 

The minerals in the subsoil are the key to vibrant veggies, fruit, berries and grass. I have fond memories, shelling fresh peas for grandparents and sampling a sneaky pea in between whistling. They were minty, a flavour almost forgotten. Supermarkets add mint to frozen peas to approximate grandmas home grown, but there is nothing quite like a mineral rich pea grown at home.

This week

I got the bobcat bogged. 

‘Fool’ my wife cried, and I agreed. A gruff chuckle and back to the hut. The excavator did not move, and the driveway is still a mess. After 5 days of rain, I got frustrated at not being productive. Now I’m frustrated about being bogged, again.

The butterflies are swarming over the tea tree flowers. Lady beetles have become the dominant predator in the garden and stinky fly traps are being setup. 

Im eating Cucumbers, Zucchini. Theres a ripe Tomato in the first week of December! my earliest yet. I’ve been watching this first tomato ripen in the heat. It turned red, so I excitedly picked it. The mouse was kind enough to clear the pulp from next years seed for me, so my taste buds will have to wait.

The competition with the currawongs for early berries is tilting in my favour. My tiny dog is doing a good job at chasing them off for now, but the balance may shift again. 

Enjoy your full tanks and remember, every day is a school day.

Stay Awesome.

The Gordon Gnohm

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