Tasmanian Institute of Agriculture research fellow Geoff Dean dug deep into the benefits of subsoil manuring at the Tasmanian Soil Science in Action forum.
Subscribe now for unlimited access.
$0/
(min cost $0)
or signup to continue reading
Mr Dean showed how soil structure could be improved with manure, using results from a trial site at Epping Forest.
This trial is part of a larger project that also covers research sites in Victoria, NSW and South Australia.
The first soil tests for this study were conducted in “Brumby” brown sodosol soil in 2015.
A combination of treatments were used: nothing (control); rip; deep rip and poultry manure; and poultry manure and straw at between 30 and 35 centimetres depth.
“The straw was put in to try and get a more efficient carbon nitrogen ratio. Poultry manure ratio is about 7:1, so it’s quite low, but the straw brought it up to about 10:1,” Mr Dean said.
The results showed the control and ripped samples were unchanged, but manure resulted in more friable soil.
“You can see the roots starting to get in there with the addition of the manure,” he said.
Growth and flowering was higher in the manured samples, but yield went down, which was attributed to the dry season.
“We had a bigger bucket, if you like, to hold water, but there wasn’t any extra water at that stage.”
The following year the tables were turned, with excess water resulting in flooding.
Results from the 2017-18 trials showed more promise, with manured treatments clearly visible at the trial site.
“It’s a pleasant change when you get such a dramatic effect,” Mr Dean said.
Again, the control and rip only blocks showed no difference, “which is not surprising”.
“It fits what we already know, which is that ripping is a waste of time, except for a few months.”
The manured sample “was way in front”.
“This is a good indication on the increased nutrient content in the manure block,” Mr Dean said.
Of the 71 trials sites involved at the start of the national project, they have been cut to 19, of which the Epping Forest site is one.
They will be cut back again to 10 or 12 for further testing at the end of this year, and Mr Dean is certain the Tasmanian site will remain in the mix.
A new trial site at Nile has been included, with more treatments, such as manure, green chop pellets, cereal straw, nutrients, gypsum, fish biosolids, sawdust and wood chips.
“We are looking at alternate sources of organic matter and surface treatments.”
NRM North funded the 2015-16 trials, while GRDC funded the 2017-18 trials.
Johanna Baker-Dowdell
Johanna has more than 22 years experience as a journalist for newspapers, magazines and online publications.
Johanna has more than 22 years experience as a journalist for newspapers, magazines and online publications.
