we're into the fun bit I'd like to introduce Rob Norton he's presenting
today's webinar crop nutrition looking back on 2017 for guidance in 2018 I'm
sure many of you know Rob he's the regional director for the International
plant nutrition Institute and has received many accolades for his work
whilst at IPN I and in his previous workplace the University of Melbourne
were elected and researched in agronomy 30 years
Roberts currently also chair of our extension Isles crop nutrition community
practice and we'd really appreciate Rob's input there today he's going to
talk to us using information from and philosophies and so rod I am now going
to give you presentation rights and may take a minute and I'll let you know when
we can see your screen it'll take a few seconds hi
I've got your screen up Rob you're good to go
all right thanks look I appreciate the opportunity to give the give a talk on
some of the issues that have come up and some of the guidance that we might be
able to derive from those issues and thanks for extension eyes for
facilitating this I would make the point that while planning is important I can't
crystal ball gaze what 2018 is going to be as you appreciate we live in a
variable environment what happened last year and what happens next year are two
different different factors all together also point out that most of you would be
aware of the extension ask company trician site website and it is a great
great resource with timely information
the other thing that I'd point out about today is that it's national agriculture
day 21st of November and you know we are in a very fast-growing industry
Australia's fastest growing industry and you know the moral is if you're fed and
dressed today you can thank a farmer for that and we all work just we all really
work for the farmers no matter who's paying us so what I want to talk about
well the first thing to start off with is to think about what the season was
like overall in 2017 it's a very famous cartoon that was in punch over 120 years
ago which was about the Kuras egg and the the bishop said that he thought
you've got a bad egg mr. Jones and the curators honored Lord I assure you
parts of it are excellent no I think a our season was also a bit like the
curating it was good in places a bear estimates from the most recent crop
report suggests that the production will be down to about 36 million tonne it's a
thirty nine percent decline on what was an incredible record of nearly 60
million tonne of winter crop which was actually about 15 million tonne more
than the previous record so 2016 17 was a was a bottler from for many people for
many growers agriculture in general and
2017 has yeah now 2007 and 18 he's probably taking us
back to 1516 in terms of production Victoria is in fact nearly twice what
1516 production was the estimates for this season
so if we look back on 2017 the map here is the Bureau of Meteorology rainfall
deciles for the past five months from June to October which is the general
growing season and we can see that just like the curate exits certainly the
seasons were good in places we had serious deficiencies lowest our very
severe deficiencies and even lowest on records excuse me in the mid north of
South Australia so you know there were very severe conditions over much of the
state much of the southeast and not so much into Western Australia but
certainly the the rainfall deciles really show up in this mid region you
know we were hoping that in our region in Victoria anyway where the rainfall
deciles weren't so bad and allow southeast of South Australia that we
were in a good in a good place unfortunately the fat lady had in the
Sun and we had to a couple of days of course severe frost the graph the top is
west near minimum temperatures west mirror in Victoria for the period from
November and basically we had very severe Frost's over those three or four
days and maybe another one coming up on the on the final day I've got the number
of minus to two degrees which is a screen temperature value and that's
usually considered as a surface frost then in the Horsham and and that
Westmere frost event coincided pretty much with the flaring of some wheat
crops and that's given a severe touch up to those and I know there's been several
crop cutter Haydon in that area here in the Willmar where I'm based the
temperatures also gave us a quite a touch up particularly on lentils and
chickpeas which were just at this early potting and early seed field stage
and losses from 30 to 100 percent generally going around so you know what
trying to give some general rules about what happens is not easy because of the
variation in in some good crops some fail crops and crops that grew well but
then won't yield any won't won't have any grain yield so what we do about
thinking about this is we we really need to think and learn from the past you
know 2017 you know what's done is done Frost the
bean the droughts are burned 2017 was different in 2016 2018 will be different
again and we can't just hope that we get another 2016 because hope is not a
strategy we need to have a plan in place in terms of crop production but but in
this case I'd particularly like to refer to the aspect of nutrient management
which is really one part of the whole farm management site cycle crop
management cycle we can divide that management up into two parts strategic
and tactical management and strategic I think things about managing approaches
for nutrients where there's a little know no other option for invention
intervention so the things we would need to do it at all before seeding and maybe
in the context of a longer objectives such as raising soil test levels or
addressing acidity with lime or sadistic gypsum and there that might be something
over a three to five year period or even longer and we would have to be planning
that at the start of the season will actually now because it's now is when
most of the growers are seeing most of their paddocks this is when they're out
harvesting seeing what's happening on the with yield maps etc and getting a
feeling for what's happening in the field that those strategic decisions are
usually around phosphorus but also around potassium
zinc and copper particularly phosphorus I'll put potassium in brackets because
in fact the effectiveness of interventions with potassium is higher
if it's done at seeding rather than done as a as a tactical approach and zinc and
copper - depending on the situation may in fact be more effective with a with a
strategic approach a long-term strategic approach and I know many growers use low
rates of zinc and copper just as a there's a top-up to ensure that they're
there levels don't decline terms of the tactical ones tactical approach this is
where interventions could be implemented in season and it doesn't mean we don't
plan them now but we plan them at the start of the season planned to be
implemented at the start of the season and we are in because of things because
of nutrients like nitrogen sulphur etc being able to be top dressed to be
effective we can modify that process during the season and we you know that
the normal nitrogen strategy is to follow your product yield levels and and
adjust nutrient inputs accordingly so obvious don't run failed many times in
terms of explaining you know this approach and in in particular in this
case I'm going to talk about the approach strategic approach to nutrients
which particularly is phosphorus and nitrogen and potassium what do we know
well Rumsfeld talked about known knowns known unknowns and unknown unknowns and
they're now known for us in terms of this year's for next year's crop really
are we know what's been removed every grower nearly every grower would have a
yield map such as the one in the bottom right corner of the screen and so we
would have a spatial view even if they don't have a yield map they would
certainly know how many truckloads a grain came out of the paddock and we may
also know some nutrient concentrations such as protein content in canola and
also in cereals and and so we do know a little bit already
about what's happened so what the removals of nutrients were we can also
know if we want if we go and take some source apples we we know what the likely
nutrient supply is and that's why we're so testing also guessing sometimes based
on history looking at using a proofs or tests to get some value as to get some
assessment of where we are and then we'll think about the now on unknowns
the big unknown for next year is what's the demand for the next for the
nutrients in the next crop and what are the likely losses of the supplied
nutrients because of the seasonal conditions or the soil conditions now
both of those are now an unknowns experience helps us transfer some of
those now and unknowns into and now know and so we can have you know use models
to look at what what potential your demands are we we've got access to saw
probes to give us ideas about water so water content but really we actually
have very little capacity to deal with the unknown unknowns simply because we
don't know what we don't know and so with nutrients obviously the first and
most important thing to think about is removal and soil testing we just
consider in terms of removal what's going out the gate that obviously
depends on yield and management and the table that I've put on here is an
example for a five 10 12 percent protein wheat crop in terms of the amount of
nutrient that would go out the gate in terms of nitrogen phosphorus potassium
and sulfur canola three-ton canola crop is pretty similar to a wheat crop a five
ton wheat crop one of the big differences is the higher sulfur removal
in the canola crop barley is about is very similar to the cereals maybe a
little more bit more potassium but not a great deal difference
those guys who had frosted frosted crops that cut first cut them for hey we'll
find that you know probably a five ton crop is probably a nine tonne per
hectare hay crop and the nitrogen going out the gate is quite a bit higher
phosphorus is pretty similar potassium is an order of magnitude higher and
sulfur is is quite a bit higher as well and that's because what we have is that
the we have the grain plus the stubble and that's double you know they're
hundred and sixty is really the sum of that wheat plus the stubble content to
get that hundred and sixty the the point is that you know where we're thinking
about hay crops we're running a lot of potassium out and if we're burning
stubble will also lose nutrients will lose maybe all the 40 46 kilograms of
nitrogen a lot of potassium bit of sulfur and not very much phosphorus the
amount loss will depend on the weather conditions around that's when between
when the stubble harvested and burned if it's wetter and a lot of phosphorus and
a lot of potassium will leach air as will some of the nitrogen so those
losses may in fact be smaller again without a crystal ball I can't tell you
how much they have much less they would be what we do know about those values
know for grains is that grain mineral contents are quite variable so even
though we might say for wheat that it's three kilograms of phosphorus to a ton
of wheat grain the blue line on this on this frequency graph is an indication of
you know the range of phosphorus content we measured in some grains which would
derive from nvt experiments over a couple of years and the median value was
three point five kilograms of phosphorous per ton on a
dry ground basis and the range was from 1800 or 1.8 kilograms
ten to four point five kilograms per ton so very large variation in the in the
concentration of grain and if you're really looking at doing nutrient
budgeting then getting actual removals by having some grain analysis is a is a
very good strategy
now phosphorus is probably the major decision that we'd be thinking about now
and so the first part of that phosphorus decision is about removal and removal
depends largely on yield so five tonne wheat crop as we've just said 100
kilograms of nitrogen 15 kilograms of phosphorus 18 kilograms of potassium
going out the gate or that 9 ton hay crop that was cut from maybe a frosted
wheat crop 160 kilograms of nitrogen 15 kilograms of phosphorus and a hundred
and eighty kilograms of potassium going out the gate if that yield of the cereal
crops only these 1.5 tons per hectare then the amount going out the gate is
proportionately less so 30 kilograms of nitrogen foreign half kilograms of
phosphorus 10 kilograms of potassium and so in terms of phosphorus if if the
phosphorus removed either has to come from source supplies and or from the
fertilizer inputs so to balance those nutrient removals in those three
examples for the five tonne wheat crop to replace what was removed would be
looking at 75 kilograms of map 200 of urea 40 kilograms of demo P if that cop
was cut too high it's 75 kilograms of map through 20 kilograms of urea and
about 350 kilograms of Merida potash we compare the five ton and the 1.5 ton
crop you know the proportion of demand then or the tenth
demand to replace the nutrients also declined so it's about 25 kilograms per
hectare of map and 60 kilograms of urea so that's just that's the removal part
the other part about a phosphorus decision is the soil supply um in us in
a soil for any particular soil the total phosphorus concentration may be 500
parts per million milligrams per kilogram so that equates to 600
kilograms per hectare of phosphorus but very little of that is available and we
measure that in terms of coal phosphorus standard phosphorus test and a coal
phosphorus score a test value of 40 equates to about 50 kilograms of
phosphorus per hectare which still sounds like a lot now some of that
phosphorus is actually in fact most of that phosphorus is actually cycling
through organic forms 20 to 80 percent of the total phosphorus in the soil is
present in organic forms and it like nitrogen needs to be mineralized to be
released into the soil solution which is where the plants the crops will access
that immediately available phosphorus there are other pools of phosphorus
which are also accessible which is where the phosphorus is or is adsorbed onto
surface part of soil particles and then there are others where other pools with
this low or very low accessibility where the phosphorus is either strongly bonded
or absorbed absorbed into soil particles or precipitated as phosphorus phosphorus
containing minerals with very low solubility so if we have the
intervention of adding a fertilizer which contains soluble PE
algebra phosphorus and also and water soluble phosphorus is also a small
amount of citrate soluble phosphorus but we'll deal with the water soluble
phosphorus phosphate first in terms of what happens to that about 25 percent or
less of that water soluble phosphorus ends up in these pools in these
available available tools and then accessed by the plant we you know you
hear all the time there's very little fertilizer phosphorous that's taken up
it actually most comes from the soil and that's true but this other 75% or more
of the applied phosphorus ends up in these lower availability pools
eventually that material will come back
will come back into these higher availability pools but it will take some
time and tboi phosphorus buffering index
changes this in some ways changes this balance of available how much has taken
up and and how much is made moved into the low available pool in high PB soil
PPI soils much of the applied phosphorus and as the lower availability pools that
goes to this side and this that's because it's tied up in acid soils with
iron and aluminium phosphate or in alkaline soils with calcium phosphates
and in that situation both of those are forming soluble are precipitated or
surface bonded phosphorus sources this can bleed back into the surface absorbed
and then into the source solution and then into the plant but the size of this
pool needs to be quite big and in some cases some of this material may be
actually precipitated and not available at all if you look over the long term
the experiments we've had here with an on and year fertilizer experiment showed
that in fact the recovery of phosphorus applied to Rick's
cropping rotation in in the Wimmer around about 85% of the phosphorus
applied was recovered in the grain add in when we applied nine kilograms of
phosphorus per year basically the crop balanced off with that removal so even
though we might say that 25% of the phosphorus is removed in fact in the
longer term this Becker is supplying phosphorus to the crop and you can't
really just distinguish between those either of those slot these are those
sides because this one this lower availabilities side of the program gets
gets moved into the more available side in many cases so we come to soil testing
and soil testing gives us an estimate of saw pea supply and this is the typical
sort of response curve of on the vertical axis of relative yield 100%
through Danil and the soil test level whatever the soil test level is and
they're defined usually in terms of a a critical range which is a range between
usually between some up say 95 or 100 percent or 90 and 100 percent of that
your potential and this is the range that you will be here you get out of the
better fertilizer decisions for crops program what those think what those
ranges tell us is a little bit about the strategy for managing phosphorus within
those critical ranges and around those critical ranges if the values are in
this lower range what we'd be looking at is trying to increase the soil test
value we'd be looking at replacement of what's being removed and we'd also have
this sort of phosphorus tax in what's being
fixed in the soil that saw a fixation will would depend on TBI as will with
this capacity will increase the soar test as we move into this critical range
we're already got the soil test value to where we want so we're really looking at
replacement value plus any losses due to soil fixation and maybe also in both
cases in all cases any soil erosion where the phosphorus particulate
phosphorus was removed and most people would think about their phosphorus in
terms phosphorus management in terms of this replacement value if we're above
the critical range then we the strategy would be to try and get that value from
down into the critical range because we have a whole resource here that's not
being effectively exploited and so we'd be maybe looking at applying less than
replacement to draw down on the saw supply and I think that's something that
we need to many growers need to to look at and we'll come back to that towards
the end with some data that I can present to you in terms of critical
Colwell P values these are the values taken from the better fertilizer
decisions for crops program project which is the repository of fertilizer
response information that's able to be interrogated and the table here is taken
from a paper by Bel Air tile in 2013 which compiled some of these in into the
crop soil type the critical values in the critical range and the critical
value is for 90 percent of relative yield the magic numbers are there that
gives you where you are sitting in terms of whether you're its efficiency
whether you're maintenance or whether you need to build soil tests the other
thing that this telic table tells us is something about where we would think
about allocating phosphorus canola is able to has a lower critical soar test
value generally than cereals and that tells us that Canole is more effect able
to effectively scavenge phosphorus in the soil so it's less responsive to
phosphorus and cereals and whereas something like peas is probably about
the same response maybe a little probably pretty much the same as
phosphorus so if we were thinking about allocating phosphorus we may consider
putting less on canola and relatively more on wheats and peas and the benefit
we actually extra benefit we get from the legumes please just being example of
legume is the response in terms of biomass and therefore fixed nitrogen
where this extra phosphorus applied the other interesting work that's come out
of the benefits program is that weed after canola tends to be more responsive
to phosphorus now put a question mark there because the data is is has been
developed and published but I think we still need a little bit more run
confirmation that with some with some more research so knowing those critical
values knowing how we manage them what's the current situation in terms of
topsoil cold-war phosphorus uh studies this is
some information that insert a pivot through the nutrition Advantage lab
currently supplied a couple of years ago looking at cropping top soil Cold War
phosphorus in Victoria over 2008 2014 and there the samples that went through
their labs and the different colors are the yellow or the mustard color is a
cold peas below 35 milligrams per kilogram so we'd say that they're cold
peas that in fact be responsive the purple line at
the top coal will please 75 a 35 to 70 the green 70 to 140 and the blue 140
milligrams per kilogram of coal P or more now I suppose the the the sobering
point about this is that if you break that down to regions in the southwest of
our state only 22% of cropping soils have coal please that would be in the
responsive range so that those guys are actually operating in the area where
they could reduce inputs the other aspect is that in the north and
northwest there's quite a large a very much higher proportion of paddocks
coming back with responsive Coble values and the central Victorian area it's very
much like the southwest so there are even so in the north and northwest even
though we have a relatively high proportion of paddocks there's still
four out of ten paddocks that are that have cold wall P values that are
indicate that they would not respond to additional service phosphorus fertiliser
so what do we do about that will we think about where we are in this in this
overall response curve and we would go to maybe a starter only or zero a
fertilizer if we've got those hearty eyesore test values so
I saw test values are above critical why would we put any phosphorus on at all
well over the years it's been consistently shown that the positional
availability of phosphorus is very important having access to fresh
phosphorus early in the season is important for crops phosphorus is in
mobile so it virtually stays where you put it in most soils and so the roots
will proliferate around that phosphorus band whereas for the for nitrogen
nitrogen will plume down it will still remain in a band safe it's Midway
abandoned but the roots can chase the nitrogen so roots need to access that
phosphorus if they do they proliferate and that helps with general crop
development an example of this was from the 2006 drought in the women aware we
were an experiment was undertaken looking at 0 and 10 and 20 and what
happened if you applied none 5 10 or 20 kilograms of phosphorus or where you
applied no phosphorus there was still some carryover of the 20 where you
applied 10 kilograms there was that not they were still a carryover where you
had 5 kilograms so small amount that in small amount of phosphorus applied in
this in the subsequent year then that phosphorus content that was able to
support yield up to what was equivalent of you know the the previous year's 20
kilogram so this always seems to be some benefit even with high soil test
failures at the long term experiment I mentioned over all sort of values and
that was Cole's up to a hundred there was a benefit between point one five and
point two five tonnes per hectare in a grain yield in weight yield
we're phosphorus was supplied at seeding the minimum amount though is probably in
the range of three to five kilograms per hectare and to supply two kilograms of
phosphorus in 25 centimeter rows that would mean that the granules are about 8
to 12 centimetres apart and doesn't matter whether that's a ma p tsp or or d
AP those granules will be you know as almost as far apart as your roots will
be within the between the the drill rows so if you go any lower than that
accessibility of those granules of the roots of the granules is is
significantly diminished so it's good to get confirmation that phosphorus is
still important even though there's our soil test that is and this is the main
picture here is from Craig Graham Italian showing really nice response
where there was a fertilizer blockage with the ma P in canola very clear
difference there so phosphorus does it is still important and another nice
picture from met Whitney in the Mallee where we there was there was a blocked
fertilizer row here and again that shows you how close the fertilizer needs to be
to be accessible to the crop as well as the impactive of no phosphorus so it's
still important balancing input and output we need to know where we are in
terms of the soil test so what about nitrogen well is three things to mention
about nitrogen first is the lidium influences from 2017 the amount that a
crop fixes legume crop fixes depends on a couple of things the first is this
nice little graph which is the soil nitrogen nitrate nitrogen a crop
establishment versus the amount of nitrogen fixed by that crop and
basically if there's a large amount of nitrogen present in the soil the crops
the the legume crop doesn't want to waste energy to fix nitrogen it will
progressively decrease the amount of nitrogen fixed in the units by its
nodules so the second part is the amount of growth and therefore also the amount
of yield and fixation and yield obviously the crop fixes but we also
with a legume crop we also remove that nitrogen you know in the grain and this
is a nice little example from Michael moody in the Malley looking at in
fixation along the along the x axis and on the y axis is how much is actually
fixed into the next crop and basically there's different crops seen here fava
beans were sort of the star performer in terms of the amount fixed and but really
only half the nitrogen fixed ended up into into the subsequent crop so high
yielding Lego legume crops are also fixed a lot of nitrogen but low that
nitrogen that's fixed is removed in this variation among legumes with lentils and
chickpeas lentils and chickpeas being at the lower end of the fixing platform
fixing scheme and filled fava beans being in the upper end
Furber things and lupins the third factor is about inoculation
effectiveness and soil pH we had some experiments down at Glenn Thompson
looking at potassium and this's and we had field put beans canola and wheat and
this is the effective nod July we had on those beans due to the fact
that the salt ph was 5 point around 5 so there was really no effective modulation
at all in this situation so the in fixation would actually be effectively
nil so these are these crops our net nitrogen uses significantly net nitrogen
users so those three factors help us think through not influences so here's
that scenario how those scenario is going to play out in 2018 well again
yeah I can't give you a crystal ball and put all those things together but in
terms of a concept about ranking paddocks in terms of their likely
nitrogen availability the highest are likely to be failed Farber burn crops
due to frost and disease that's likely have the most nitrogen available good
bean crops are likely to have still even though the yields are high still likely
to fix a lot of nitrogen and then as you go down failed lentil crops due to frost
if there are failed pulse crop due to drought they probably didn't grow much
anyway so there was not much nitrogen fixed and then we go into canola crops
good canola crops good wheat crops cut for hay and good wheat crops cut for
grain so I can't tell you how many kilograms a table it would be but that's
about the ranking of your of the paddocks there's some interesting work
here about canola crops seeming to preserve some nitrogen from one season
to the next so that canola which that's grown on canola tends to be able to
access relatively more nitrogen because the roots of canola had some inhibitory
chemicals which reduced the rate which are about you effectively nitrification
inhibitors and so canola crops are likely to have a wheat growing on after
canola crops is likely to have a yet allow our nitrogen requirement because
some of the cannot nitrogen is carried through
if the processes from now that will determine how much of that nitrogen
carries through to our seating to the ceiling that's obviously your most
processes that affect both mineralization any mobilization and
we've got rainfall and temperature of course crop residue management whether
you burn bash or bury or bail and also what the rainfall and we're sorry what
your weed control program is in terms of those words exploiting the nitrogen and
the water so the processor from now will determine the nitrogen status at C D so
how much do we need them at seeding well if there's 30 to 50 kilograms at seeding
that's probably enough to get through and that's in a whole profile it's
interesting that the figure up in the right top right of the screen is some
work that Glenn Macdonald summarized looking at the yield response with
nitrogen as sowing versus the yield response with nitrogen Egeus 30 and it
actually works out to be almost a straight line so there was no particular
difference between top dressed in crop nitrogen and that seeding nitrogen and
in fact we'd sort of I've sort of been making the observation that rate is in
fact more important than timing and source a provider we have enough
nitrogen at seeding to get us through and in a lot of cases we would have that
the only issues there are a couple of issues with nitrogen and seeding and
nitrogen deserting is the time when we know least about your potential and when
we have the highest seasonal risk and highest unknown risk of how the seasons
going to play out so putting all your eggs upfront is not a really good
strategy there's also potential for seedling damage if there's high rates of
nitrogen placed in furrow in one of the interesting areas that grab sandals been
working New South Wales is looking at mid row
skipper abandoning of urea as a way to get high rates of nitrogen in its eating
but keeping it away from plant roots the other aspect about seeding versus later
application is how many opportunities are there for in crop application in the
lower rainfall and even in the very high rainfall areas the the number of times
when we can get on fields and the number of times we can get rainfall events to
wash nitrogen in tends to be limited so if we think about those factors we may
decide to have more nitrogen at seeding and probably this year on on big crops
anywhere has been big crops or cut pro for high it may be important to have
more nitrogen at seating but thing is to sorted the other aspect is to I think is
to use a nitrogen rich strip most of you are now been banging on about this for a
long time but it is a way of making estimates of
mineralization and denitrification and leaching in in your field across a
landscape and it's our able to monitor what's going on in the in those paddocks
and the thing about them is interesting comment by Mark Branson from South
Australia's saying that it actually allows him to decide when he doesn't
need nitrogen and he says that's the that's the aspect that safety more
dollars over the years we these processes are running pretty well
another aspect of application is making sure you get the
application of the fertilizer right application evenness you're putting
fertilizer on the last thing you want to seize is stripping in the paddocks and
this is pretty obvious that the fertilizer spread has not been set up to
the right bout with but we also said in the lower picture even when the
spreading pattern is is pretty awful really and we saw this in a couple of
fields weather this year where there was hired nitrogen demand so it real 2017
with high nitrogen amount we're really played out as areas that didn't have a
very good spreading showing up so using a cue spread and foot care become quite
important effort karakurt alert spreaders to make sure they're able to
spread to the widths they advise just a couple of things about potassium and a
couple of the other nutrients and be aware of potassium deficiency the sort
of key here is a light sandy soils high rain all and we're high cutting is
occurred and you saw the figures they're a tenfold increase in potassium removal
for a wet croppers cut for hay versus one that's um a strip for grain you can
look for the diagnostics such as that patches that the urine patches look for
win dry effects where there's better growth in the wind rows and you might
even consider trying a potassium rich strip and 50 kilograms at least at
seeding potassium and sulfur are both macronutrients they behave quite
differently
potassium behaves more like phosphorus it's not very mobile sulfur be hot
behaves more like nitrogen and so the fundamental principles of potassium and
sulfur a management become sulfur is more like nitrogen which we would manage
technically potassium is something we we would manage like phosphorus we would
manage that strategically so although we might like to think of
potassium as being soluble and easy easily accessible it does get bound up
on the soil codes and particularly on heavier soils will become have low
mobility final word about the micronutrients the conditions at which
they become more or less available are determined by a whole range of soil
conditions such as obviously saw pH we all know about but a waterlogging
or drought drought restricts root growth with sin restricts a capacity data for
the crop to access some of these micronutrients high organic matter soils
will reduce the availability particularly of copper but increase the
availability of zinc because the zinc is more easily mobilized these are what
more easily mineralized in those in those processes phosphorus content can
affect the availability of some of these micronutrients as can the soil texture
as can compaction so you know these are the things that will play out in the
season to come and it's worth just keeping an eye on some of those
micronutrient conditions if it becomes waterlogged or drought and particularly
on particular on specific soil types
just finally it's not all about nitrogen and phosphorus alone we really need to
consider balanced nutrition I just want to go quickly through an experiment one
experiment we had in 2016 at bull lagoon in South Australia which was a canola
crop this is what the site looked like so it was a little wet I think it was
actually in bulla Geun not near bull lagoon the yields in the end top yields
were three three and a half tonne of canola and the two bars you can still
set two bars you can see there are where we put 60 kilograms of nitrogen or 30
kilograms of nitrogen with all the nutrients supplied so we gave at the
rolls-royce of fertilizers treatments and then if we put no fertile
and the difference between those is the response to fertilizer you can also see
is where there was low nitrogen there was very little extra response so
nitrogen in some ways was driving the ability of this crop to express its your
potential if we took and looked at the 60 kilograms of nitrogen treatments and
then dropped out phosphorus or potassium or sulfur or the trace elements what we
see is that there was a significant decline in sorry there was no real
significant difference you know any of those nutrients the potato phosphorus
level was declined a little but it wasn't a significant difference the
others were all pretty much on par with where we supplied them also if you
looked at that you would conclude that there was no need for phosphorus if you
then put more nitrogen on this time a hundred kilograms of n one hundred
percent of n in fact the the differences become expressed quite significantly so
we we have the situation here sorry we have the situation here where where you
have a adequate in supply to make the yield water limited your potential in
fact where there was no phosphorus the crop was in fact phosphorus deficient
and so the difference there is about 25 percent if you added phosphorus between
this blue bar and the blue bar at the hundred at the all and the other thing
we saw was that sulphur actually also became fell out as being something that
was limited in supply so if we dropped the soft rail at the out of the
fertilizer program it was it led to about a 15% yield decline but those only
occurred when we had high level of nitrogen so that's where this
interaction between nutrients becomes important and pushing towards the most
limiting factor in a lot of cases Nitra is very important and we would like to
and make sure that water becomes a limiting aspect not nitrogen or
phosphorus or suffer any of the nutrients and just a final comment about
a survey I did with southern farming systems supported by GRDC which we
looked at 500 paddocks over three to five years from Victorian and southern
New South Wales and we estimated the amount of nutrient that was going in and
the amount of nutrient that was being removed in in grain and hay or however
else being removed we took a count of fixed nitrogen and the the graph here
the blue graph is for nitrogen and the measure that we have is what's called
the partial nutrient balance so that's that's the amount of nutrient going in
to the amount of nutrient going out so at one that means there's as much
nutrient being removed as being supplied as we go higher in those values so two
for example means that there's twice as much nutrient being removed as being
applied and 15% of fields 15% of those paddocks over five years had twice as
much nitrogen removed as being supplied and that's coming from mineralized
organic matter and in fact 60% of those fields were in mining nitrogen
effectively mining nitrogen out of the soil that's a challenge to work out
farming systems will reduce that mining the other aspect was with phosphorus and
in some ways was almost the reverse where we had our partial nutrient
balance the amount of phosphorus removed this is supplied only 50 percent of
fields with mining phosphorus and about half about a quarter of the fields were
in fact removing and twice the amount of phosphorus that saw
they were applying twice the amount of phosphorus was that was being removed
now there's certainly saw a fixation there but the question is with these two
graphs would you be thinking about substituting some of your fertilizer
phosphorus budget for your fertilizer nitrogen budget so with that fish and
just do a quick summary about about our strategies was obviously saw testing and
doing nitrogen budget and no surprises there
invest in nitrogen early between BC 1355 take a short-term view with view or a
tactical view with nitrogen fixed nitrogen on file legumes it's hard to
see a bonus but that may be a bonus the only bonus we get from those their crops
phosphorus at sowing is the only real option banded placement near the seed
row is a really important strategy for phosphorus we should be thinking taking
a long-term strategic view adjusting race rates to offtake plus a tip if the
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