What happens to carbon in the soil after biochar is applied?


Welcome everybody, great to see you all attending
from different parts of New South Wales. So welcome to the July Soils Network of Knowledge
webinar. Okay, now I’d like to introduce and I will
say it properly, Zhe Weng, hope I got that right, but I will refer to Zhe as Han, as
he’s more commonly known as in Australia, who is presenting today’s webinar. And the webinar is ‘What happens to carbon
in the soil after biochar is applied? Han is a third year UNE PhD student of Lukas
Van Zwieten, Dr Lukas Van Zwieten up at Wollongbar Primary Industries Institute and his thesis
topic is biochar stability and its role in native soil carbon and root derived carbon
stabilisation with field and laboratory investigations into those mechanisms. Han graduated from the University of East
Anglia in Norwich in the United Kingdom with a BSc honors degree in Environmental Sciences
but much more excitingly Han received the prize for the best presentation by an under
35 year old for this year’s, oh last’s years, National Soil Science Conference held
in Melbourne in November last year. Thank you Luke and thank you for attending
today’s webinar. So today we talk about what happen to soil
carbon after biochar is applied. In a research aspect for those of you not
familiar with Biochar I’ll give you quick introduction. Biochar is a carbon rich product which derived
from thermal desorption of literally any organic matter in a carbon low environment. It looks like charcoal here, as you can see,
but it’s different. So the main difference is how we produce it,
as I say before, it has been produced in a no oxygen environment and also it can be made
of literally any material. So what biochar for then? Why use biochar? Biochar can use as a soil amendment if you
want to improve your soil fertility. This has been many literature show biochar
has ability to improve crop yield, increase water holding capacity. Biochar can be also used as approach for waste
management. For instance, the waste water management biochar
can use as a sorbent. Also biochar is kind of a bi-product from
biofuel generations and most recently there is a lot interest in use of biochar as a carbon
sequestration approach which I will tell you more about today. And there is a term we are going to use very
often today, it’s called the ‘Priming Effect’. So what is priming effect? Priming effect is defined as the change in
the turnover rate of soil at organic carbon after you apply some substrates. In this case we talk about carbon but not
necessary, sometimes nitrogen can also introduce priming but today we focus on the carbon priming. So how priming works? As you can see in this diagram, and in these,
the texts, this in white bar is a soil organic carbon, once you put carbon substrate if the
soil organic carbon doesn’t change its no priming. If after you apply the substrate there is
increasing soil organic carbon turnover so you have more CO2 emissions. This is a positive priming. Vice versa if there is a decrease in soil
organic carbon turnover this is a negative priming. So over the past decades there are thousands
of literature based on biochar applications. Many of them focus on the stability or the
longevity of biochar. However, many of the study has been conducted
in a laboratory environment but very few studies was done in the field, which is where we are
going to apply the biochar and not often have a focus on the biochar plants or biochar-root
interactions as you can see in this picture here. So, to measure is to know. We set up two field trials at Wollongbar DPI
to assess first how stable is fresh biochar in the field in a ferrosol and a subtropical
climate which also being used as a new (or annual) ryegrass pasture and how biochar interact
with soil organic carbon and plant derived carbon. Secondly, we are interested in how biochar
interaction with soil carbons can change over time. As you can see this famous picture here is
terra preta Australis which is created centuries ago by the Australian Aborigines. So to start set up of first trial and top
picture shows that’s a snapshot of our Wollongbar DPI, nice and green here and we measure the
soil respirations also for the first time we introduce a soil plus root respiration
chambers from which we can study the biochar plants interactions and we also use a stable
isotope technique to quantify the root respirations which I am going to show in more details in
a minute and this all, methodologies and the results was documented in our latest paper
which recently accepted by Soil Biology and Biochemistry, hopefully will come on line
very soon. So let me tell you more about stable isotype
techniques which help you to understand how we get our results. Like everybody have a driving license in nature
there is a driving license for all the elements which this driving license is given in terms
of the carbons 13 signatures. Each element such as air, biochar and soil
have their own identical signatures which different from each other as you can see in
this diagram here. They all very different which give us a opportunity
to separate each sources. So we use, an alkaline trap in our respiration
chamber here, from which we can capture total CO2 emissions in the traps then we can determine
the total carbon 13 signatures and use a mathematical equations we can separate the biochar carbon
mineralisation and the soil mineralisations in this two pool system. So I am not going to show the equation here
just you know that’s early start, that’s too much for mornings you know, if you want
to know more please find our paper. So unlike the two pool system where you only
have soils and biochar a planted system has never been published in literature the reason
because this three pool systems have the plants the soil and the biochar which interact with
each other can change the soil, the total emissions and it is very hard to quantify,
for this we introduce a novel group soil respiration chamber where you can see in the middle it’s
exactly like the soil respiration chamber I show you before but on the side we have
a so called root growth chamber from which the plant is grown and the roots can grow
through the root windows which on the column here inside into the chamber within which
we can measure the soil, plus biochar plus plants respiration. Just to quickly show you. This a snapshot taken inside of chamber shortly
after harvest. As you can see there is some white very fine
living roots onto the surface and use those mathematic equations we can quantify the root
respiration chamber and as you can see here there is three different signature. So for the post labelling we introduce a carbon
13 enrich environment which gave us a higher root signal from -25 to 150 so can quantify
the root respiration in here. As you can see the biochar had no impact on
respiration. So will plants have the impact on biochar
carbon mineralisation then? Again we show plants actually did not change
the biochar mineralisation. As you can see the difference is within the
margin of error and we use a model to estimate the Mean Residence Time of biochar in our
particular system which will quantify, which we estimate to be around 449 and 483 years
in the planted or unplanted system. Again this is within the error which means
it is no difference. So, you may ask what is different? Why you talk to me something not different? Now here as I described before, the priming
effects which shows actually in the planted system, when the plants interact with biochar
there is a decrease in soil organic carbon turnover. So there will be less CO2 emitted from biochar
planted system compare to non amended soils as you can see here. In most literature the timescale of the studies
only is about three months to half year, so in that short period you can see there is
a plus peak here which means there is increase of turnover of soil organic matter, however,
over time there is a decrease. The reason it is exciting is because the most
studies don’t include plants which as you can see overall is around zero. There is no priming. There is no change. But in the real world where the planted is,
in a practical system we show that this biochar can reduce the mineralisation of soil organic
carbon and now we wonder what happen for this very impressive results can change over time. Whether the biochar still can reduce the soil
organ carbon loss or not? So we go back to visit existing trial which
was set up in 2006 by Lukas Van Zwieten and Steve Kimber. Where they put two type of biochar into the
soil system. One is beef-lot manure biochar and the other
one is green waste hardwood biochar and they found this very rapid increase in soil organic
carbon shortly after 36 months and then most impressive increase was delivered by hardwood
biochar back then it’s called green waste biochar and we wonder what happened to this
particular treatment after 9 years aging in the field. So I was very fortunate to be offered the
opportunity to step back to this historical site and use the very similar setup as I show
you previously. So we look at four treatments in this site. The first one is un-amended soils, we call
it control. Secondly we look at 9 year age biochar, which
was applied 10 tonne per hectare roughly 1% to the top 100 mm soil depth and also we apply
exactly same biochar at the same dose in the top 10 cm and also we wonder what happen if
we apply fresh biochar to the existing aged biochar plots. For instance a farmer’s want to increase
their yield before the biochar slowly reduce the effect so he thinking about doing second
application. So that what this last treatment about. A secondary application of biochar. Again this is our old friend and in this case
you can see this biochar signature is very similar to the plants so to avoid this we
used the pulse labelling to enrich the root signal again. From which we can quantify the root respirations
as you can see before treatment here the control, the fresh biochar, aged biochar and the second
application. Again biochar treatment had no impact on root
respiration but interestingly we find that the field aged biochar can reduce soil organic
carbon turnover rate so called the negative priming. This time both the planted system and the
unplanted system show the same effect, biochar slowed down the soil organic carbon loss. This might explain why we still observe a
further increase in aged biochar plots even after nine years. Again in the second application we applied
fresh char into aged char plot you have a cumulative increase. It is very rapid shortly after four months
and the black line here shows the calculated total soil carbon which equals to the soils
carbons plus the biochar additional carbons and we find actually there is a margin here. The green here shows its actual measurement
of the total soil and this might partially be explained by the negative priming we observed
earlier. So, just bear with me, to conclude we show
that biochar did not impact root respiration as we found the roots did not change biochar
degradation rates either and this particular hardwood biochar in our study system induced
a significant negative priming of soil organic carbon so it’s reduced the soil organic
carbon loss and such negative priming may account for the increase in total carbon even
after eight years. So in established trial Lukas and Steve show
there’s a rapid increase in total soil carbon after biochar application and we show if you
add more chars in the existing biochar plots there is a further increase in total soil
carbon and we were wondering what happened if you adding more chars into the soil. Whether there’s like a limitation? Whether there’s a capacity to holding more
carbon in this pasture system? So I like to thank this very important people
for their emotional and technical support. Without them, all I could show today is just
some titles and some beautiful pictures. So thank you for your attention. Back to Luke. Luke:
Well thank you very much Han. That was very interesting. I have Peter Entwhistle here. Peter:
My question was the rates of the biochar that were used in the original trail that Lukas
put down. Han:
Yep, its 10 tonne per hectare into the top ten centimeters of soil, so it is equivalent
to about 1%. Peter:
Ok. Han:
So when we do the new trial on top of the old trials we used exactly the same dose 10
tonne per hectare too and also the same biochar. Thank you. Peter:
Ok, thank you. Luke:
Ok, we’ve got a question from Eddie Joshua. Eddie:
Hello Han, I’m just wondering if there is an ability to change commercial compost production
systems into a biochar production system so that when people are composting green waste,
we could actually make it into biochar and spread that instead. Han:
Yes, there has been many literature based on the use combining compost with char as
well and of course there is a way to actually convert compost system into a char system
but I’m no expert in engineering but I know a lot of people who do, like Stephen Joseph
or Lukas Van Zwieten or Steve Kimber and there is a way to do this but it really depends
on whether it’s kind of economic and also in terms of energy bills and what do you really
want this biochar for cause its biochar can make of any organic matter as I’ve mentioned
before and also when you apply biochar you have to tailor biochar for specific purposes. Like if you want to use biochar for its fertiliser
kind of ability you have to use probably something like a manure or high ash content chars. For composting I think char can reduce emissions
to start but it depends on the water content of your compost too. So I think it is possible but I am no expert
in this area so I think you need to ask some kind of specialist but there are definitely
a way Eddie. Eddie:
Thank you. Han:
Thanks. Luke:
Thanks Eddie. Helen Wheeler, so here is Helen’s question
Han ‘For the graph showing fresh biochar plus fertiliser , aged biochar plus fertiliser
then fresh plus aged biochar and Helen’s question is was the total amount applied larger
than the fresh, plus aged than the individual fresh or aged? Han:
Yes, the fresh plus aged char is 20 tonne per hectare. It is large it is not compare with the single
dose it just look at the second applications. So the fresh and aged chars they all 10 tonne
per hectare the fresh plus aged is the 10 tonne per hectare fresh char applied in the
existing 10 tonne per hectare aged biochar in the field so it makes it 20 tonne per hectare. It is larger. That’s why the black calculated line is
much taller than this two line here. Thank you Helen. This graph is loads of information so I just
pinpoint some very interest findings and just try not to confuse you but thank you for giving
me the opportunity to clarify this graph. Luke:
Thanks for that Helen. Ian Packer has asked a question. Ian:
How you going? Just gut feelings about the use of biochar
in your drier climates and your poorer soils like your red/brown earths and things like
that and the economics of it all. I know we haven’t got any data. Han:
Yep, so we start with it dry. It’s actually this is a subtropical environment,
we call it a very guarantee rainfall every year. It is not really a dry environment. It is warm and it is humid so it is not dry. For economics, I haven’t done any economics
on this particular trial yet but there are some life cycle analysis done by Annette Cowie
and also in the existing trial. We find this the hardwood biochar didn’t
increase the crop yield if you want to know something to do with the economics, but as
I also say there is a manure biochar which significantly increased the crop yield because
it changed the phosphate availability, so, but, it is not as stable as the hardwood chars. It really come back to the point what do you
want to use char for, whether you want to have a shot at increasing yield or you are
really kind of thinking the carbon budget to use as a trading kind of a mechanism but,
and there’s a new way is like combine the two chars or do you also enhance biochar which
is clay cultured chars either manure or urea which is kind of a slow release kind of biochar
if you like which can somehow make it more cost effective if you like but thank you for
the questions. Luke:
And just to clarify Han, I think what Ian was saying in areas like ours that are drier,
how does it apply? Is that right Ian? Ian: Yeah, well yeah, we probably won’t
get the same reaction in the drier climate. Han: It is very different. There is also a trial we also involving in
Nationwide trials which also down in, there’s one down in Tasmania on the same, similar
soils ferrosols as well, which the climate is totally different. It is cold and it is a bit wet too so it is
really kind of system specific. If it is really dry, during our experiment
actually we also find if during the dry season the kind of mineralisation will slow done
over all because you have to have water for the plants also there is not much kind of
interaction from the bugs as well in the soil. So actually it is kind of it’s more likely
to slow down but also because of the clay soil what we use. If you were talking about sandy soil and those
not very fertile soil it is most likely biochar may not work as a charm did in our specific
system. So again you have to tailor the char to meet
your need. Luke:
Great and thanks to Steve Kimber I’ve unmuted you Steve if you’ve got a phone? Steve:
Just getting back to Ian Packer’s question, I don’t think the sort of rates we are putting
here on the coast would be applicable to your western systems and Han alluded to the Western
Australia work where they were actually banding at planting using much lower rates, it might
even be in the, just in the hundreds of kilos per hectare because the cost of the biochar
is quite significant and if you are doing that sort of application year after year with
the types of residence times that Han’s talking about you are going to build up your
soil carbon in any case. But I wanted to make a comment originally
that this study is in a permanent pasture system and it would be interesting to look
at a cultivated system and see whether you are still going to get that same sort of accumulation
of carbon or whether the oxidating effect of turning your soil over regularly is going
to reverse that process. Luke:
Great Steve, thank you. Thank you very much for a very informative
webinar and thanks for everybody attending and especially to Han for such a great presentation. Han:
Thank you everybody. Thank you Luke, I appreciate your time and
effort. Thank you very much. Luke:
Ok. Thank you everyone, we will end it there.

Leave a Reply

Your email address will not be published. Required fields are marked *