Australian farmers and scientists trial new methods to improve soil moisture

They have teamed up with researchers from the University of Southern Queensland to run a trial to see how cover cropping affects soil moisture and yield.

Australian farmers and scientists trial new methods to improve soil moisture

By Kate Doyle

Recent rainfall has come as a huge relief for many, but after years of drought baking dry soils, some systems are taking a while to recover.

“The last few seasons have been difficult. The last four have been below average but the last two in particular were the hardest we have ever had,” according to southern Queensland farmer Dave Woods.

But since late 2020 things have really turned around on Dave and Alice Woods’ broadacre farming operation north-west of Goondiwindi.

“It is a huge relief. We knew it would happen at some stage but the trouble with drought is you never know when that is going to be,” he said.

Infiltration woes

Rain is of course key, but it is not the only factor required to produce a good crop.

After years of the sun baking their bare paddocks, the first summer crop after the November 2020 rainfall was disappointing for the Woods family.

“It was really interesting because we were getting lots and lots of rain but the rain was mostly running off and we were actually infiltrating very little of it and that was quite a shock to us and we realised there was a bit more to it,” Mr Woods said.

“We realised we needed to be doing a lot more to infiltrate the soil and better utilise it.”

To better understand their soils, Dave and Alice Woods are trialling several different techniques, including deep ripping and cover cropping.

They have teamed up with researchers from the University of Southern Queensland to run a trial to see how cover cropping affects soil moisture and yield.

Every few weeks PhD candidate Hanlu Zhang gets out to the farm to monitor the experiment.

Back at the lab, she tests samples from the field and simulates how the system is responding to cover crop management and how that impacts on the crop yield and soil health.

“[This] … will help us do an overall system analysis and help farmers to do more science-based decision making,” she said.

According to project supervisor Afshin Ghahramani, a senior research fellow at USQ, soil moisture is important because there is uncertainty in seasonal forecasts, but we can know how much water there is in the soil.

The risk with cover cropping is that the cover crop itself takes moisture and nutrients to grow.

But Dr Ghahramani said initial results suggested cover cropping could improve soil carbon while also holding more moisture through until the time of sowing.

“It’s not only about increasing soil moisture it is about the availability of soil nutrients too, so we might be looking at the trade off between them,” he said.

“We might decrease soil moisture but on the other hand increase the nutrients available to the plants,” Dr Ghahramani said.

Multi-species crops

Building on this concept, Dave and Alice Woods have another trial paddock where they have planted an eight-species crop.

“Every one of those species has its own set of root exudates that are stimulating biology in the soil. We only understand a tiny fraction of that but we do understand that each of them plays a significant role,” Mr Woods said.

“It is all about understanding how different plants collaborate rather than how they compete for moisture,” he said. 

Not only is the multi-species crop benefiting the soil, it is providing tasty grazing for cattle and humans alike.

“People think we are a bit crazy growing eight things in one paddock,” Alice Woods said.

“It is a bit of trial and error. We don’t really know if it is going to give us the benefit that we want, but we won’t know until we have done it for a few years,” Dr Woods said.

Alternative methods

Cover cropping is not the only way to improve soil moisture.

According to Zvi Hochman, chief research scientist at CSIRO Agriculture and Food, genetic work is underway.

One approach is to encourage earlier vigour, bringing about quick ground cover and preventing moisture loss.

Another is to develop species with long coleoptiles, which are the protective sheaths surrounding the shoots as they make their way from the seed to the surface.

Species with long coleoptiles can be planted deeper so there is some safety that they will only germinate when there has been enough rain to penetrate deeper into the soil and produce a crop.

“All of these are subject to current research and development and are being trialled on farms,” Dr Hochman said. 

“How it will land will depend a lot on the area you are in, how suitable it is for that area and what niche you find for these technologies,” he said.

Variability set to increase

The research could prove timely, as variable rainfall years are set to become more common, according to Dr Hochman.

“One of the aspects of climate change is that we expect to get more frequent droughts and more frequent wet periods,” he said.

“So although Australian farmers are terrific at handling variability, it is going to become more challenging in the future than it has been in the past and we are already seeing that.”

Luckily, farmers like Mr Woods are up for the challenge.

“The great thing about agriculture in Australia is that it is constantly evolving,” he said.

“Generally speaking, I think farmers in Australia do an incredible job to produce in a climate that is very volatile and that leads to a lot of ingenuity and a lot of creativity and some ground-breaking research.”

Originally published at Abc news