CONVENTIONAL cropping practices with monocultures and synthetic fertilisers have led to "dysfunctional" soils, according to respected NSW soils ecologist Christine Jones.
Instead Dr Jones - who was speaking at a Limestone Coast Landscape Board seminar at Kybybolite earlier this month - said to restore soil health, farmers needed to replace their high inputs with practices that encouraged more diverse life in the soil.
This was best achieved through plant diversity - growing four different plant families or more in the one paddock - and replacing synthetic fertilisers with a biostimulant, such as seaweed or compost to activate soil biology.
"In monocultures, plants compete with each other but we don't see that when plants from different families grow near each other," she said. "They complement each other and are more resistant to pests and diseases and drought tolerant."
Dr Jones explained that in every single seed, as well as plant DNA and nutrients for energy, there were up to nine billion microbes, which were extremely important.
This microbiome largely determined how quickly the plant germinated and how well it establishes in the soil.
"The genes of the plant will determine what kind of plant it is but its microbiome will determine how healthy it is, how fit for purpose it is and how it responds and interacts with the resident microbes in the soil," she said.
During establishment, the seed worked out which microbes it needed to release into the soil for root development and which microbes it could use from the soil.
"We need to plant a diversity of seeds because legumes have a different microbiome to grasses so if you have plant diversity you have microbe diversity," she said.
"If you are a weak plant, there is not much point using your neighbour for their microbiome if they have the same microbes but if the roots of different plants are close together, they can borrow microbes."
Dr Jones said microbial DNA in seeds could be enhanced or depleted across successive generations with fungicides considerably weakening numbers.
She was also critical of ag research that found the nitrogen and phosphorus fertilisers enhanced growth and yield.
Much of the research has been conducted in greenhouses under conditions which were not conducive to soil microbial activity, she said.
"We have soil that has been destroyed for months if not years," she said. "It is all homogenised and sometimes it is sterilised and put into pots so the only way that the plants grow in a monoculture of wheat is with applied fertiliser. This is a totally dysfunctional system, fertilisers are just viewed as a necessity but they are a substitute to microbial activity."
In Australian soils Dr Jones says there are huge amounts of phosphorus unavailable to plants from decades of application and microbes could make this more available to plants.
"Work done by the CSIRO has found there is a $10 billion phosphorus fertiliser bank," she said.
She said farmers who were concerned about exporting phosphorus off their properties in meat and milk should test for total P rather than Colwell P.
Dr Jones was pleased to see the growing recognition in some countries about the importance of multi-species crops and pasture systems, with the Irish government giving a 50Euro per bag incentive (about half the price of a bag of seed) to establish polycultures.
"The government is actually recognising the importance of diversity. When dairyfarmers just plant ryegrass they use massive amounts of N and they have N going through the ground water," she said.
"Most of the Irish water is contaminated with nitrates and it cost the governments a lot to get the nitrates out so people can drink it - it also contaminates the waterways."
SE FARMER CHANGES CROPPING PRACTICES
Kybybolite farmer Sam Schinckel has sown 19 different cereals, brassicas, clovers, herbs, oilseeds and grasses together in each of his cropping paddocks.
After watching several videos of United States regenerative agriculture farmer Gabe Brown speaking about the benefits of plant diversity and reading about a few local farmers who had put multi-species cropping principles into practice, he says it made sense to give it a go himself.
ln 2021 he trialled 35 hectares of cereal and small seeds sown together and was so impressed by the yields of both species when graded after harvest, he has sown all of his 300ha of crops to multi-species.
"The year before we had an issue with the amount of root disease in the wheat crop," he said.
"Half of the paddock didn't grow but last year in that same paddock we were able to grow a good thick crop."
Mr Schinckel has increased the diversity in his 2022 mix with 100kg/ha of large seeds, such as beans, peas, lupins, wheat and barley, as well as 10kg/ha of the smaller seeds including chicory, plantain, linseed, clovers and grasses.
Single super was broadcast on the paddocks early in the season at 100kg/ha and a knockdown herbicide was used prior to sowing but Mr Schinckel has no plans for any other inputs. He says it is a matter of deciding whether to graze the crops, cut for hay or continue to harvest.
"The biggest issue is the seed cleaning after harvest and not having anything to sell off the header if you want to, but the savings on inputs and work plus the plant and soil health outweigh any of these drawbacks," he said.
