North west pits lessons
From the December 2008 edition of Agriculture Today.
A Healthy Soils for Broadacre Cropping course staged at various locations in the north west of the State during the past 12 months gave the one hundred and ten participants plenty of practical lessons.
"They will be able to manage their farms differently as a result," said soils scientist Graeme Schwenke, one of the team from Tamworth Agricultural Institute (TAI) who put the course together.
"As well as learning about functions of a healthy soil, all participants in the course got to assess the health of their own soil samples with some basic hands-on testing plus lab testing for soil biology, diseases and plant nutrients."
"Each group also learned to assess several whole soil profiles in pits dug on a member’s property, stressing the often forgotten importance of subsoils, which can be difficult to access," Dr Schwenke said.
His NSW Department of Primary Industries colleagues, Sally Muir, David Herridge, and Lachlan Rowling, were on hand to help.
Dr Schwenke said most participants in the course came from mixed farming enterprises, although there were some from areas of all cropping.
Participants also learned to assess their groundcover - crucial on land recovering from drought - and their previous crop’s stubble disease risk.
On the positive side, laboratory tests at TAI showed 31 per cent of stubbles brought in had a high level of infection by tricoderma, a beneficial fungus species that decomposes crop stubbles.
However, Dr Steven Simpfendorfer, head of the DPI disease management laboratory, also found that 14pc of samples submitted carried a high risk of crown rot. Only two per cent had a high risk of common root rot infection.
While much of the northwest NSW cropping region is dominated by what scientists term "vertosols" (grey-black cracking clay soils), farmer groups from around Coonabarabran and Coonamble brought in a wider range of lighter soil types to compare and test.
Dr Schwenke said each group devised what they considered to be the most important soil health issue for their local area.
"Some of the focal issues included dealing with subsoil constraints, better matching crop and variety to soil type, persistence of nitrogen-fixing rhizobia for legumes, dealing with acid soils, making no-till work on hard setting red soils, better understanding soil phosphorus, and better understanding soil tests," he said.
"Most soil tests on samples the farmers brought in showed no likely problems, but there was some indication of poor soil health.
"For example, most soils brought in had good soil pH, but 14 per cent were sufficiently acidic to warrant addition of lime for best cropping results.
Plant nutrients were more an issue with 20pc of samples deficient in sulphur and 50pc deficient in phosphorus, based on known critical levels for wheat crops.
Groundcover in participant’s paddocks was rated as poor in 26pc of responses, leaving the land in those cases at high risk of soil erosion and poor rainfall infiltration.
Most paddocks had been farmed for many decades with an average 48 years of cultivation history.
Contact Graeme Schwenke, Tamworth, (02) 6763 1137, graeme.schwenke@dpi.nsw.gov.au
