PROJECT UPDATE: TOP SOILS & SOIL CORING

Vic Drought Hub - Farmland 1
GAgG Drought Adoption Officer Nicole Frost on one of the demonstration plots.
GAgG Drought Adoption Officer Nicole Frost on one of the demonstration plots.

Topsoil – buy it or create it?  

 

Project lead: Food and Fibre Gippsland (Gippsland Node)

Focus area: Soil

Update: December 2023

Project status: active & on track

Expected end date: May 2024

External partner:  Gippsland Agricultural Group

 

You can read more about the December 2023 update in our Projects page. Credits for all images: Gippsland Agricultural Group.

 

Buy more topsoil or make more? And is that even possible?

 

By Lyric Anderson, Gippsland Agricultural Group

 

The “Growing more topsoil” demonstration at the Gippsland Research Farm, run by Gippsland Agricultural Group (GAgG), always creates a lot of discussion. Explaining the thinking behind wanting to rip up an entire paddock is best left to project leader, Rick Blackshaw, also GAgG’s Drought Adoption Officer.

 

“Rather than buy another paddock at who-knows-what per acre, what would it look like if we invested $1,000 an acre in land we already have? And how long does the benefit last? Because we need to find a way for our soils to be more robust,” Rick said.

 

The paddock in question has been deep-ripped to a depth of 300-350mm, incorporating the first 100mm of topsoil with the underlying clay.

 

It’s an unusual thing to do at the very least, and is an attempt to answer the questions:

  • Can we substantially increase our water-holding capacity in our topsoil?
  • And can we double our topsoils from 150 millimetres to 300mm?

 

The project began on 30 June, 2023, and the results were showcased at GAgG’s last spring field day, with pits dug in the demonstration plots to show the effect on the subsoil.

 

Rick ran sessions on both the Growing More Topsoil demonstration and Soil Amelioration demonstration.

 

Rick is leading a 5-year project jointly funded by Meat and Livestock Australia to look at the practice of soil amelioration in its capacity to increase water and nutrient-holding capacity and overall soil health, while F&FG ­– in its capacity as the Gippsland Node of the Victoria Drought Resilience Adoption & Innovation Hub – has also invested in the Growing More Topsoil project.

 

Giffard farmer Trent Anderson (L) and GAgG Drought Adoption Officer Rick Blackshaw examine the subsoil of the demonstration plot.Three ways of using additives

 

Within the demonstration are three distinctly different ways of using additives to create better soil.

On hand at the Spring Field Day were GAgG chief executive officer Trevor Caithness, soil expert Peter Norwood of Full Circle Nutrition, and soil scientist Bill Grant from Vic Hub partner Federation University, who had each taken on a plot using their chosen method to achieve a doubling in topsoil:

  • The Fed Uni method is to balance soil chemistry and structure incorporating soil compost as the primary focus
  • Full Circle Nutrition is aiming to balance trace elements in addition to core macronutrients
  • Farmer group, concentrating on traditional sources of fertility and standard machinery

 

Although he wouldn’t usually recommend such an extreme activity as deep ripping, Bill Grant openly acknowledged the demonstration was dealing with “very challenging soils”.

 

For Rick Blackshaw, the investment in soils is probably more viable than buying the neighbour’s place.

 

“These amendments are also aimed at increasing water penetration and holding capacity and we’ll inter the green manure crop we’ve grown to help that,” Rick said.

 

“A lot of people at the field day wanted to see it grazed, so we’ve listened and will graze it with cattle, then we’ll inter the manure and remaining trash which should get the biology and fungi going beautifully.

 

“We’ll take another core sample next year and measure the tonnage grown, as well as the soil’s capacity and structure in each of the three plots.”

 

Details

 

Project description

To help farmers increase their knowledge, confidence and skills in building a more robust topsoil with increased water and nutrient-holding capacity. This project began on 30 June, 2023 and will explore and demonstrate three different methods to develop a more robust topsoil to better deal with climate variability. Each plot was deep ripped to a depth of 300mm with the top 100mm of topsoil incorporated into the next 200mm of clay subsoil, half of the control plot was left with no intervention. The plots were then speed disced and planted. Before sowing, each plot was allocated differing rates and types of fertiliser.

 

Plot 1: control

Half the control plot had no intervention; the other half was deep ripped and speed disced.

 

Plot 2: Federation University advised

This plot aims to balance soil chemistry and structure with compost as the primary focus. Compost was applied in the north and a compost/gypsum blend was applied in the south

 

Product Rate

Urea 100 kg/ha

3:1 Super Potash 200 kg/ha

Compost (north) 26 t/ha

Compost/Gypsum blend (south)12 t/ha

 

Plot 3: Full Circle Nutrition advised

This plot aims to balance all plant nutritional requirements for optimal plant development to a depth of 300mm.

 

Product Rate

Gypsum 1,000 kg/ha; lime 1,000 kg/ha; chook manure 4,000 kg/ha; guano/RPR 200 kg/ha;

SOP 100 kg/ha; Agrisilica 500 kg/ha;

90 sulphur 90% 75 kg/ha; zinc sulphate 36% 10 kg/ha; copper sulphate 25% 10 kg/ha

Manganese Sulphate 28% 25 kg/ha; boron granubor 15% 12kg/ha;

Cobalt sulphate 21% 1kg/ha; sodium molybdate 100 g/ha;

Selenium chip 1% sodium selenite 1kg/ha

 

Plot 4: Farmer advised

This plot aims to use traditional sources of fertility and standard machinery to increase the topsoil depth.

Product Rate

Gypsum 2.5 t/ha; lakes lime 8t/ha; poultry manure 5t/ha;

3:1 Super potash 500kg/ha; copper sulphate 25kg/ha; zinc sulphate 25kg/ha

Manganese sulphate 25kg/ha; boron 10kg/ha

 

Green manure crop

 

A green manure seed blend from Barenbrug which included ryecorn (10%), oats (10%), barley (10%), faba beans (30%), lupins (20%) and field peas (20%) was broadcast on 4 July, 2023. It was then lightly disced and rolled and was followed up with 4mm of rain.

The green manure crop was going to be incorporated into the soil to provide extra fertility and biomass in the top 300mm of soil, however, due to popular demand from the farmers who attended the field day at the demonstration site, the green manure crop was grazed by 127 heifers.

The remaining manure and grass is to be incorporated, which will be completed when conditions allow.

Soil testing and pasture cuts will be taken in the future to measure potential changes in topsoil and yields.