A KEEN interest in healthy soils has been the motivation behind a project promoting best cultivation practice on several vegetable farms across Australia, focussing on tillage.
A farm walk at Lindenow in southeast Victoria recently brought people from as far afield as Tasmania to discuss the project and results to date.
Three trial plots at Bulmers Farms, Lindenow, looked at soil conditions that can be created in vegetable plots to determine best return in cropping, while looking after soils and the surrounding environment.
A conventional cultivated plot was disced, ripped and bedformed and two plots – reduced till and no-till – ripped and bedformed.
Spinach was planted into the conventional and reduced tillage bays on July 7 last year and a second spinach crop was planted October. It was followed by lettuce in early November.
Between crops, the conventional bay was off-set disced and deep-ripped and the reduced tillage bay was deep-ripped.
A mustard cover crop was planted on July 7 in the no-till bay, mulched mid-September then sprayed and lettuce planted early November, for harvesting mid-January.
Agronomist Ben Winter said the lettuce yielded heavier in the no-till bay, with 650g heads, compared to 400g heads from the conventional bay.
Baby broccoli was the next rotation, at the start of March, which has been picked several times.
A major issue at transplant stage was the need to modify machinery, which held the crop back.
“This project challenges what we do on a commercial basis and we need to keep challenging ourselves in what we do and what we’re going to change in the future,” Andrew Bulmer said.
“We’re committed to trying to do the right thing for our region’s environment.”
Soil scientist Dr Kelvin Montagu said the focus was on incorporating cover crops into the crop rotation in a way that reduced input costs, increased yield and resulted in a more robust system.
“We want to go back to what our fathers and grandfathers did in their day, reducing tillage and fertiliser use,” Dr Montagu said.
“We’re not tying to be idealistic, but treat tillage as a tool and use it to our best advantage; while relying on the biology of the soil to do a job rather than the tractor.”
The three trial plots have been underway for 12 months and have presented some challenges; but the no-till bay has already shown significantly positive impacts.
“After 10 months, the no-till plot is full of holes and the biology of the soil has created holes for the roots to move through,” Dr Montagu said.
“We’ve let the bugs in the soil make an environment ideal for sowing, just by excluding tillage and using some cover crops.
“The sub-soil was markedly better in the no-till plot that the two cultivated bays.”
The no-till bed measured 80 tonnes/acre of organic matter - old alluvial soil with high quantities of charcoal, an active carbon.
“What we’re building with the reduced till is active carbon, it’s currently less than 5 per cent and we are wanting to build it – and we do that by using cover crops,” Dr Montagu said.
In comparison, he said the two cultivated bays had shown collapsed soil with no capacity to enable roots to move through it.
There have been significant advantages to using cover crops and no-till, according to site manager, Daniel Hammond.
“From six months until harvest, our ground is worn out and compacted; when we go back into cover crops that helps us to break down the compaction, build up the soil and gives us some control over weeds,” he said.
“Using the trial plot practices, on a commercial scale – we can come out of a cover crop straight into a baby leaf, without tillage cultivation – then after harvest some light cultivation then a baby leaf again, keeping the cover crop.”
He said planning and crop rotation on a broader scale needed to incorporate the time it takes to break down the cover crops and using cover crops had given better results in use of fertilisers, soil moisture retention and baby vegetable yields.
“The reduced tillage trial plot sat pretty much between the two other plots, except the subsoil was much better in the no-till plot,” Dr Montagu said.
“It’s an easy step in-between the two extremes. It looks a bit rougher but we still grow good crops on it.
“Obviously with conventional tillage and discing you’re dealing with the crop residues, but you’re also disrupting the soil and burning off the organic matter – and you’re always drawing from the organic bank for nutrients.”
Dr Montagu said reliance on heavy machinery and intensive tillage practices for broadacre vegetable production needed to change.
“We need to build robustness back into the soil,” he said.
“We want to reduce the passes and the impact on the soil, the disturbance on the soil microbes, increase organic carbon and make the horticulture industry a lot more sustainable.”
*Watch a video from the day here.
