IMO we would do well to do more agrichar trials in more places, sooner rather than later. Australia seems to be on point here.

The huge potential of agricultural soils to reduce greenhouse gases and increase production at the same time has been reinforced by new research findings at NSW Department of Primary Industries' (DPI) Wollongbar Agricultural Institute.

Trials of agrichar - a product hailed as a saviour of Australia's carbon-depleted soils and the environment - have doubled and, in one case, tripled crop growth when applied at the rate of 10 tonnes per hectare.

10 tonnes per hectare, about 4 tons per acre, is a lot of material to handle, so this is a non-trivial expense even if the material is free. It may be best done over a couple of years, especially if used as a top dressing rather than being incorporated through plowing or disking.

NSW DPI senior research scientist Dr Lukas Van Zwieten said soils naturally emit about 10 times more greenhouse gas on a global scale than the burning of fossil fuels.

"So it is not surprising there is so much interest in a technology to create clean energy that also locks up carbon in the soil for the long term and lifts agricultural production," he said.

The trials at Wollongbar have focused on the benefits of agrichar to agricultural productivity.

"When applied at 10t/ha, the biomass of wheat was tripled and of soybeans was more than doubled," said Dr Van Zwieten.

"This percentage increase remained the same when applications of nitrogen fertilizer were added to both the agrichar and the control plots.

"For the wheat, agrichar alone was about as beneficial for yields as using nitrogen fertiliser only. "And that is without considering the other benefits of agrichar."

Regarding soil chemistry, Dr Van Zwieten said agrichar raised soil pH at about one-third the rate of lime, lifted calcium levels and reduced aluminium toxicity on the red ferrosol soils of the trial.

"Soil biology improved, the need for added fertiliser reduced and water holding capacity was raised," he said. The trials also measured gases given off from the soils and found significantly lower emissions of carbon dioxide and nitrous oxide (a greenhouse gas more than 300 times as potent as carbon dioxide).

Other investigators have noted that the relative neutralizing value (RNV) of char for acidic soils depends on what the char was made from and how it was made. But even at 1/3 the RNV of lime the change would be significant since so much char is used. Those with calcareous soils could not use it unless they buffered the alkalinity, perhaps with sulfur.

Trials to determine whether the benefits of char were still present in such a scenario are needed IMO since the same type of results come from using lime to raise the PH of acidic soils. I'd like to see trials that used char, lime and wood ashes such as those from energy cogen plants since they all raise PH. Wood ash also has some primary and secondary nutrients, though no nitrogen. It may be that char has them as well, again depending on what material was used to make the char.

All of these soil amendments reduce the need for fertilizer in acidic soils since soil chemistry improves, and that reduces soil emissions from bacterial decomposition of fertilizers. Better use is made of the nutrients that are present in the soil. All of these amendments provide some nutrients as well. This improves the fertility balance of soils which in itself reduces the need for some primary nutrients such as nitrogen. Growth improves and the health of plants and soil microorganisms improves as well.

It would be good to focus on the benefits that are unique to char, if any. There's one we are sure of - it sequesters carbon in a durable form. That alone is reason to use char as a soil amendment, but the case would be much stronger if there were other benefits not available elsewhere.

NSW DPI environmental scientist Steve Kimber said an added benefit for both the farmer who applies agrichar and the environment is that the carbon in agrichar remains locked up in the soil for many years longer than, for example, carbon applied as compost, mulch or crop residue.

"We broadly categorise carbon in the soil as being labile (liable to change quickly) or stable – depending on how quickly they break down and convert into carbon dioxide," he said.

"Labile carbon like crop residue, mulch and compost is likely to last two or three years, while stable carbon like agrichar will last up to hundreds of years.

"This is significant for farmer costs because one application of agrichar may be the equivalent of compost applications of the same weight every year for decades.

"For the environment, it means soil carbon emissions can be reduced because rapidly decomposing carbon forms are being replaced by stable ones in the form of agrichar."

Unfortunately, agrichar is not widely available. BEST Energies Australia, a company involved with NSW DPI in the trials, has a pilot plant at Gosford which is producing minimal amounts for research purposes.

Again, carbon isn't the only thing you get with crop residue, mulch and compost. If farmers don't apply these amendments then the shortfall must be made up another way, and must be done repeatedly. An integrated system that considers all of these issues is required. Char may be a magic bullet, but it isn't as magical as advocates and activists are claiming. I fear that overselling it will create a backlash and hamper adoption of the technique. Farmers can be dour, doubtful, hidebound and stubborn about new fangled products. It's best to tell the story strait.