2014 Stubble Technical Forum
Project Partners:
Wednesday 5 March, 2014
Corowa NSW
Stubble Research Forum
Wednesday 5 March, 2014
Corowa RSL Club, Corowa, NSW
9 -9.30am
Coffee on arrival
9.30am
Welcome and brief overview of the day’s events
9.35 – 11am Keynote address – Pauline Mele and Lori Phillips (DEPI)
‘Soil biology and its relationship to carbon’
11 – 11.30am Morning tea
11.30 – 1pm Research overview
(Graham Centre, Riverine Plains, Harm van Rees)
1 – 1.30pm General discussion and wrap up
1.30
Lunch
25/02/2014
S il O
Soil Organic Matter update
i M
d
Harm van Rees, Cropfacts P/L
BCG, SFS Vic & Tas, MSF, FarmLink, CWFS, Hart, EPARF
Two fractions influenced by management
• Decomposing plant and animal material
• Unstable (months to years)
• 0.05 to 2mm
• Decomposed material attached to soil particles
• Stable (decades)
• <0.05mm
Third fraction Charcoal
Soil Function
Particulate Organic Carbon (POC)
Humus Organic Carbon (HOC)
Physical functions
√√√
√
Chemical functions
X
√√√
Biological functions
√√
√√√
1
25/02/2014
Increasing soil organic matter
Particulate: Stubble retention and reduced
tillage
Humus: Apply sufficient nutrients for the micro‐
l
ffi i
i
f h
i
organisms to break down stubble into humus (5.8 kg N, 2.2 kg P, 0.9kg S / t stubble)
Increasing soil organic matter ‐
farm groups working together
Stubble standing
+/‐ nutrients
Stubble incorporated
+/‐ nutrients
Stubble removed
+/‐ nutrients
Trials commenced in 2012 – all plots soil sampled Last year of trial work 2015 – repeat soil sampling
Summary • Three fractions – Particulate, Humus, Resistant
• Different beneficial attributes ‐ dependent on soil type
• The greatest benefit of increasing SOM is from i
increased N (Humus fraction)
d N (H
f ti )
• Continued research to quantify the benefits of SOM is funded by GRDC and the Federal Dept. of Agriculture
2
Increased soil carbon by accelerated humus formation from crop residues Dr Bill Slattery – Soil Scientist, Project Officer with Riverine Plains This project is investigating whether fertiliser (nitrogen, phosphorus and sulphur) applied to stubbles before sowing will lead to an increase in soil humus. Project sites are located at three locations; two on dryland agriculture at Culcairn and Rutherglen and one on irrigated cropping country at Tocumwal. Treatments include stubble mulching, stubble standing and stubble incorporation (plus stubble burning at the Rutherglen site). It is proposed that a larger proportion of the crop residue carbon (possibly double) will remain in the soil as humus, rather than be lost to the atmosphere, if nutrients are applied to aid and increase soil biological functions. In addition there are different rates of fertiliser nitrogen applied at sowing (normal rate, half the normal rate and no fertiliser) to investigate whether split rates (pre and at sowing) can provide economically viable yields and build soil carbon at the same time. The project will also monitor nitrous oxide emissions and thus identify the overall impact of fertilising stubble residues on greenhouse gas emissions. Project funding: This project supports the Australian Government’s Securing a Clean Energy Future plan by creating opportunities in the land sector to cut carbon pollution. Specifically this project will investigate the opportunity to reduce carbon pollution and increase the amount of carbon stored on the land. A key aspect of the ‘Action on the Ground’ program is to understand if this practice is economically viable within current cropping systems. The project will also determine if the overall greenhouse gas budget is a positive one taking into account any additional nitrous oxide emissions with pre‐sowing fertiliser applied to stubbles. Project Partners: The project is a partnership between Riverine Plains Inc., the Murray CMA, North East CMA, and the Integrated Cropping Council, and property owners: Godde Farms Pty Ltd (Culcairn), E.G. Baker and Co. (Rutherglen) and Glendaloch Pastoral Company (Tocumwal). Results to date: Although this year’s grain yields at all sites were affected by late frosts (the Culcairn site more so than the others) there are some positive findings in the first year. Early crop observations during tillering showed considerably more vigour in the stubble standing treatments at all sites. This was supported at harvest by a trend in higher yields for the stubble standing treatments at the Rutherglen and Tocumwal sites. Yield data at the Culcairn site was significantly affected by frost and what would have been a bumper crop yielded zero on many plots. Although there is a general trend to increasing yield with increasing fertiliser rate, results do demonstrate that with some stubble treatments there are penalties in yield at the higher rates of fertiliser. However these results were confounded by soil pH variability and frost damage. It is hoped that results this year will shed better light on this important aspect of plant nutrition. At this early stage in the project it has not been possible to demonstrate a change in soil carbon values between treatments, but it is hoped that with the adoption of speed tillering in this year, as the incorporation treatment, a small change will be observed in soil carbon between tillage practices. Other soil data showed a significant variance in soil pH across each of the sites, something that is not unexpected over the 8 – 12ha size sites. It has been possible with the number of soil samples collected across the sites to identify how many samples are required to provide a good indication of the pH of a paddock, especially for liming purposes. For example the entire 108 soil samples at the Rutherglen site gave a mean pH in Calcium Chloride of 5.3 with a variance of ±1.4, this variance increases to ±2.1 with 25 samples and ±4.8 with 10 samples. The question is how accurate do you want to be and how many samples can you take and indeed how would you collect these samples. I will discuss this a bit further at the Stubble forum in March and look forward to discussing this project further. Profitable & sustainable carbon
cropping for
f Landholders
DAFF - Action on the Ground
Carbon Cropping –Iain Hume – Div Resources Research – 5 March 2014
Partners
Aims
 “Kirkby” Theory
– Stubble has high C low N
– N, P and S needed for max conversion to
Humic C
 New Research Model
– NSW DPI/CSU ~ Design & analysis
– Farmer Groups ~ liaison & technical input
– Farmers ~ test sites & feedback
1
Treatments
 Control
 Stubble Incorporation
 Stubble Incorporation
+ Nutrients
Treatments
 Control
 Stubble Incorporation
 Stubble Incorporation
+ Nutrients
2
Treatments
 Control
 Stubble Incorporation
 Stubble Incorporation
+ Nutrients
Measurements
 Soil Carbon
 Stubble load
 Productivity
Design ~ Spatial data
 Balance EM31 & 38
with other spatial
data
 Accounts for
paddock variation
3
EM Data
EM Data
Classification
EM 31
EM 38
4
Classificaton
Class
EM31
EM38
Site
Blocks
5
Treatments
I+
I-
C
Treatments – no blocks
I+
I-
C
Was the design worth it?
Variability – in TOC
a.
l.s.d. (P=5%)
In Plot
Between
Plots
Chance
of bias
Blocked
0.021
0.112
18%
0.34%
Unblocked
0.073
0.091
78%
0.53%
Based six samples per treatment strip. Fewer samples = less precise estimate
6
Soil Carbon
 There is no bias in starting values
– Any difference will be due to treatment
 Differences between sites
Difference in TOC & HOC
0-10 cm
10-30 cm
7
Rainfall Effect
Total
Ratio
0-10 cm
10-30 cm
0-10 / 10-30
TOC
P=0.037
ns
P<0.001
POC
ns
ns
ns
HOC
ns
ns
P=0.018
ROC
ns
ns
ns
8
Many sites = better results
 Rainfall effects
 Detect treatment effects better
– TOC single site lsd = 0.34
all sites lsd = 0.20
0 20
Many Sites = More people
9
ENABLING LANDHOLDERS TO ADOPT PROFITABLE AND SUSTAINABLE CARBON
CROPPING PRACTICES
KEY FINDINGS FROM THE GROWER GROUP INTERVIEWS
Group interviews were conducted in June, July and September 2013 with a sample of landholders from each of the
six grower groups involved in this project. The aim of the group interviews was to provide baseline data on
landholders’ knowledge, understanding and practices of stubble management. Findings from a thematic analysis of
these interviews are provided below. Individual in-depth interviews were also conducted with two landholders from
each grower group to enable more detailed insights into stubble management practices. The results from the
individual interviews will be presented in future reports.
Theme 1
Despite widespread interest in, and use of, stubble retention, burning remains an
important management tool for many landholders
Most participants in the group interviews were interested in stubble retention and routinely used it as part of their
farm management practices. A range of benefits were reported including: timeliness; water-use efficiency; lower
labour intensity/lower costs; moisture retention; nutrient retention; and, improved soil structure. Improvements in
the soil were particularly valued with one grower observing that “the benefits in the soil are just far outweighing the
cost of the potential problems” (Southern Farming Systems group interview).
However, despite the benefits, many growers also favoured the burning of stubble where appropriate. This was due
primarily to the production benefits associated with burning, lack of social pressure to change, and the need to
retain some flexibility in stubble management practices (Table 1).
Table 1: Motivations for burning stubble
Motivation
Examples
Improved production and/or
financial viability
I spoke to a farmer the other day who burnt his stubble … to get his Trifluralin
properly incorporated. That’s the only reason he did it and he’s a farmer that
doesn’t normally burn. (Farmlink group interview)
At the end of the day we’ve got to make money and if it means burning the stubble
once every now and again to get that crop, to get the chemicals to work, to have
that crop a better crop, well we can do it. (Rural Management Systems group
interview)
Lack of social pressure to
change
Flexibility in farm
management practices
We live in quite an intensely populated area and I haven’t experienced any sort of
social pressure from my neighbours to cease burning at this stage. They all just see it
as part of the annual cycle. (Rural Management Services group interview)
No pressures, I think it’s just harder to get the permits … the requirements of the
permit are ridiculous really, over the top. (Southern Farming Systems group
interview)
Yeah, you’ve got a toolbox with a whole heap of things there and … one of those
things might be a match. I’ve never burnt stubble myself but, you know I’m not
going to condemn someone who does. (Central West Farming Systems group
interview)
A box of matches is in the toolbox. They’re sitting right up the top. (Holbrook
Landcare group interview)
1
Theme 2
Burning remains an important option for landholders due to a range of challenges
associated with stubble retention
Having the option to burn stubble was considered important also due to a range of challenges associated with
stubble retention such as technical constraints in getting through the stubble when sowing, biophysical constraints
which make stubble retention difficult in certain areas, lack of production benefits, pest and weed management
problems, and the variability in production systems (Table 2).
Table 2: Challenges associated with stubble retention
Challenges
Examples
Technological/technical
constraints
You’re really restricted by the implements that you have and your row spacing and
whether it’s a tined implement or a disc implement. (Rice Research Australia group
interview)
A lot of machinery can’t handle *stubble+, it can’t (Southern Farming Systems group
interview).
Biophysical constraints
In this valley, in here where it’s high rainfall, heavier soils and heavier trash
management generally speaking with traditionally up until now narrow growth
spacings, a lot of that work [stubble retention] is very hard to implement. (Holbrook
Landcare group interview)
It’s not easy to be in full stubble retention and not burn in this area, it’s not easy. It
can be done but it’s not easy. (Southern Farming Systems group interview)
Lack of production
benefits/higher workload
Until there’s a direct link between saving stubble and earning more money, it’s
always going to be a feel good situation I suspect and I don’t know that there’s any
direct link at this stage, well in terms of sort of benefits to our cropping program, I
don’t think there’s been any major benefits established yet and there certainly isn’t
any benefit to our sales program in terms of being able to achieve better sales.
(Rural Management Services group interview)
It all depends on what you want to do with the paddock because incorporating
stubble sometimes means extra work whether it’s putting the big disc through it or
whether it’s mulching it or whether you’ve got the implements to actually get
through it. (Rice Research Australia group interview)
Pest and weed management
problems
There’s probably, in most cases there’s advantages to burning it. There’s problems
when you keep it, there are pests that you’ve got when you keep it, weed
management is hard when you keep it. (Farmlink group interview)
I think the slug pressure that we got from the previous year, people were very
worried … about what was going to happen and the easiest thing was to put a match
through it … It’s probably the cheapest way of … dealing with a heavy stubble load.
(Southern Farming Systems group interview)
Variability in production
systems
Theme 3
And it obviously, it varies too if you’re dry-land cropping, it’s a lot easier to go into
row sowing on a big area than if you’re in completely, in an irrigated environment
because you just, you know you don’t, it’s very difficult to actually inter-row sow
and, you know… or actually sow on an angle so you can get through the stubble as
well. (Rice Research Australia group interview)
The use of stubble retention to sequester carbon is a low priority for landholders
As a consequence of the above challenges/constraints, growers were sceptical of stubble retention as a technique
for sequestering carbon. Scepticism centred on four inter-related issues: lack of clear benefits for the farm business;
2
problems of biophysical variability in sequestering carbon; limitations in quantifying and accurately measuring soil
carbon, and lack of conclusive scientific evidence on the benefits of stubble retention in increasing soil carbon (Table
3).
Table 3: Limitations of stubble retention in sequestering soil carbon
Limitations
Example
Lack of clear benefits for the
farm business
As farmers, there’s got to be a pretty good system in place before we can actually
make money out of it. So from a stubble management point of view I think that’s
the, that’s the last thing on the tick list that we should be looking at, not the first
thing which is my concern with a lot of these projects. (Rural Management Services
group interview)
I’m not that sure of what the rules are but if you sign up and your carbon levels go
down, do you owe them money? Yeah well bugger that. (Southern Farming Systems
group interview)
Biophysical constraints
I don’t think we can sequester carbon in these low rainfall environments, and it
hasn’t been proven yet. (Central West Farming Systems group interview)
The problem is in periods of drought your soil carbon’s going to reduce … naturally
anyway and that’s when you can least afford to be paying the government back for,
or paying whoever is running this carbon market. (Rural Management Services group
interview)
Problems of accurate
measurement
They seem to be able to think that they can measure the output, but from a farming
soil across the whole country, they haven’t yet been able to work out, what are we
talking around Urana to here, what carbon’s in it and benchmark it from that. So it
varies from year to year and it varies from paddock to paddock and it varies from
zone to the State. (Holbrook Landcare group interview)
[Carbon sequestration may] save the world … but it’s difficult to measure and
difficult to quantify. (Rice Research Australia group interview)
Lack of conclusive scientific
evidence
The world thinks that we can … increase soil carbon with carbon priced at a
ridiculously low price and yet there’s no [conclusive] science that backs up the idea
of increasing soil carbon in agricultural systems (Farmlink group interview).
I reckon there’s a lot of research need to be done on it. I think there’s a long way to
go before they can make a conclusive argument against something, against carbon
and how it’s sequestered and all that sort of stuff because you don’t, I don’t think
that they really know what our farming practices do and how it releases it. (Rice
Research Australia group interview)
Conclusions
Grain growers have a high level of awareness of the biophysical, production and environmental benefits
associated with stubble retention.
However, for many growers there exist a range of challenges and constraints that contribute to problems in
achieving these benefits.
Consequently, burning remains important for growers as part of their stubble management ‘toolkit’.
Retaining stubble to sequester soil carbon is not a priority for growers. There are few perceived benefits and
many growers are sceptical about the science as well as accuracy of soil carbon sequestration.
For further information on the social research component of this project please contact Vaughan Higgins: (02) 6051
9623 or [email protected]
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Contacts
Dr Pauline Mele
Principal Research Scientist - Biosciences Research Division, Agriculture Productivity
Department of Environment and Primary Industries
T: 03 9032 7083, E: [email protected]
Dr Lori Phillips
Research Scientist – Biosciences Research Division, Agriculture Productivity
Department of Environment and Primary Industries
T: 03 9032 7141, E: [email protected]
Dr Iain Hume
Research Scientist
NSW DPI
T: 02 6938 1984, E: [email protected]
Associate Professor Vaughan Higgins
Associate Director – Institute for Land, Water and Society
Charles Sturt University
T: 02 6051 9623, E: [email protected]
Dr Bill Slattery
Soil Scientist
T: 0439 741 880, E: [email protected]
Dr Harm van Rees
Cropfacts
T: 03 5439 5085, E: [email protected]
NOTES