experiment andwe have also undertaken other related research, someofwhich has

266 Pages·2012·21.4 MB·English

CSIRO
AUSTRALIA
Division of Soils- Waite Campus
WaileRoad, Urrbrae. SAPostalAddress: PrivateBag No. 2. Glen Osmond.SA5064
Telephone: [phone] Fax:[phone]
May 6, 1996
MrJolyon Burnett
HRDC
7 Merriwa St
Gordon, 2072
Dear Jolyon,
Asrequired by the HRDC Board, Iam forwarding toyou with this lettercopiesofall
ofmy papers and articles thatwerepublished as a result ofthe research
undertaken under HRDC grant NY004. The research reported ina couple ofthe
earliestpapers would havebeen startedduring the period prior to 1990,whenIwas
in receipt ofa grantfrom theRural Credits Fund. Also, someresearchthatmight
have been initiated duringthe 1990-1993 period was notwritten up until later Itwill
be reported under NY314.
Alsoenclosed is an interim report from me to Scotts regarding NY425. As indicated
overthe phone, thewrong fertiliser was suppliedfrom the Netherlands,so the
results could not be published. However, Scotts have funded an additional
experiment andwe have also undertaken other related research, someofwhich has
been published in Australian Horticulture and someofwhich isyettobe written up.
Itrust that these reports will meet the needs of your Board.
Yours sincerely,
Kevin Handreck, FAIH
Australian Science Australia Future
NT^CIAA
PROPERTIES OF POTTING MIXES
Areoort of three years of research that was carried out during
the period 1990-1993 with the help of HRDC Grant NY004.
Chief Investigator: Mr Kevin A. Handreck
Technical Assistant: Mrs Jenny Anderson
Organisation: CSIRO Division of Soils
r
6 SL&-
RESEARCH
Iron can partly prevent
phosphorus toxicity
Kevin Handreck, FAIH
effects of phosphorus on plants will grow happily in soil-less potting
Readers of Australian Horticul
ture may recall an article of prone to phosphorus toxicity, and mixes either without any added P or
mine "Supplying iron to plants gives practical guidelines for these with as little as one-tenth of the
additions needed by other plants.
growing insoil-less media', published plants.
If these plants receive more P than
m the July 1989 issue. It was
Plants vary in P requirement this they can show their dislike
intended to be the last word on the
subject, for a few years anyway, but Anattempt togrowthevastmajority through blackening and death of
of plants in soil-less potting mixes their oldest leaves and perhaps
some further research results have
without any phosphorus (P) in the eventually the whole plant and/or by
dictated otherwise.
fertilisers used will mostly give stunt yellowing of young leaves.
In this series of two articles I want
ed plants with dark and purpling These are the P-sensitive species.
to share with you (he main con
leaves. Most plants need something They are found mainly in the protea
clusions from several experiments
like 10-50ppm P in a constant liquid and legume families, in such genera
involving the supply of iron to
plants growing in soil-less potting feed or several percent P in a slow- as Acacia, Banksia. Brachysema,
C/wrizema, Eutaxia, Grevillea,
release fertiliser.
mixTehsi.s first article shows that iron But there are a number of Austra Hakea, Lechenatiltia, Protea and
can help counteract the adverse lian and South African plants that Pultenea. They are also in
Basic facts ab^pho^
^exarriple,^% :by-vplume;pf'.a;red 'iplants-in soil-less potting.mixes
•jThe^concentration 'of tptal^P ;in"
^sbiUfrom'the.DanderiongTrariges of^ >should- have,a,P.;concentration of;,-;
pinebarksus^
.-.about -60g'";P^per cubic\metref-~,v .Victoria;.Will reduce^availability i-at least lOppnrforii 'constant'feed '->
^equivalentA(of'.about'-'^.6kg/mJVb'y a(cid:127) bout,f90%,^ w&leXthe•same.i(cid:127) and up to perhaps~50\ ppm for-lessi-
v'sin'glcfsuperph6s^ ' amountof other'day.soils-,reduces ,'frequently.,:applied -feeds. '" -—(cid:127)(cid:127) (cid:127)(cid:127)
:pf-this ;Pc4s;'readily'.available70,;,;P'avaiiability^by only 30%.• ,,;..-\ i- ';"(cid:127) - (cid:127) .'(cid:127) -v" r-V.'- ''(cid:127)... e'v;-v." -'£
Acknowledgements ;
'most plaritsJji/V^-'v ;-';, r.-.S'v. (cid:127) '"''(cid:127)
.•The' concentration- pf:,;available, single superphosphate-:range' up to %The-'fihahcial supportofthe:Horth,
Vp'(cid:127) naturally>present:;ih;-many peats. c'1.5kg7ni3;Jfof"general'1nursery pro- iculturarRese'afch.and Development. .
;.icprp'pfation\is^gra'tefully ackriowl-1 ;
!is--higher-than^.thatfisupplied by .^ductipn,:'ibut-when' drainage from
^pihe.'baric-and ,sawHust7-unless'of Jpots^is.likeiy^such high applications f'edged'.-: -kA''- -,v ":'(cid:127),-'• *''"(cid:127)''''(cid:127)(cid:127)
•course.;=these.Have'}had^P^^dded. ^are-wasteful and;can contaminate
IRefeirences^...;^^ .-n :
Vduring;co'mposiing. p-i,; "',-;(cid:127)(cid:127).'- ".-(cid:127) --..-ground and surface waters.;
(cid:127) i-The'-''(cid:127)components;; :of_; 'soij-less",••Additions shouldv"ber'na'more >Grierson, P.Fr and Attiwill/ P.M. :.
.media haveonlya small ability to than 0.5kg/m3 whena:slow-release')(1989). 'Chemical,characteristics pf .
hold'P, so most of any addition"of .."fertiliser;.(cid:127)abler to.'release^adequate v-the proteoid.root,mat-of Banksia-
': P in-soluble/form;:(such:-as.'"the•., amounts^of.P is.used,-aridMean be ' integrifolia V',;Ausi.,J. Bot.31>
;superphosphates) is leached,from =vzera., -'(cid:127)'(cid:127) V.;;(cid:127)(cid:127);(cid:127)• ,(cid:127)(cid:127)(cid:127)_,(cid:127) vJ-i^/V; _ ;'137-143, (cid:127) \'~t'/:'. * *"'
.pots-;within weeks..(cid:127)--.'"'(cid:127) --'{'--'"' C"«.The concentration^' pKP in. a t'. .Handreck, K.A->.-(.l?89): 'Supply-.
• Vermiculite,' perlite, rice hulls, dilute D.TPA;:extract (a .chelating ' ing iron to^plants',growing in soil- '
diatomite, -charcoalr;and washed.-..agent), as prescribed.in theAustra Ue'ss media-'-, XustyHortr 81(7): 72-
lian"standard forspotting mixes, is.V82.;. .(cid:127) :>;-.i\.r ^'- "' - "(cid:127)(cid:127)(cid:127)
sands comprised mainly of quartz
do .npt^affect.the availability of P > reliable indicator of'th'e^level.of (cid:127) NicholsV D,G. (1988)::iNutriti6n;.
.Iand^.fertilizer rnaterials'.'- In; Proc. ,
^included-in potting,mixes:,\v<-V'r ^'available:;R'ihVa-;'pptting .mix. ';•-.:".
j-Seminar' on'-Pptiing^Mixes, Artarr"
"•Natural;.soils', reduce. P' avail- .;-• Liquid;;feeds^that are.tp,..,supply
frnon,;Aust/ihsuHprtvT-pp. 16-30:.
.;..ability'*to,,.different,7extents.: )For ;-all of the(cid:127) R*to'.•'general .nursery
Australian Horticulture. June 1991
24
:^.SH- ^"-.
RESEARGH
Baeckea, Bauera, Boronia, Dryandra, Table 1
Hypocalymma, Pultenea and Maximum concentrations of P tolerated by species growing in
Eucalyptus. (Nichols, 1988). a soil-less potting medium at two levels of extractable Fe.
The old leaves that prematurely
fall from these plants when they Fo (ppm)
receive too much P have concentra 34 19
tions of P that are about 10 times Acacia merrallii, Grevilica ieucopteris, Hakea bucculenta,
higher than those found in healthy <3
H. francisiana, H. petiotaris
green leaves. These old leaves have A. imbricata, Banksia benthamiana, B.brownii, B.temanniana,
<3
been poisoned by' phosphorus. B. leptophylla, B. sphaerocarpa, G. banks//, H. salicUolia
Yellowingofyoungestleaveswould A. baileyana, A. decurrens, A. spectablis H. sericea
5 3 A. dealbata, A. glaucoptera, A. ligulata, A. lineata, A. montana, ^
normally be taken as a sign of iron
8 7
A. myrtifolia, A. retinoides, H. laurina J[{
deficiency. This symptom can occur
B. trlcuspis, H. rostrata "**.'
in some P-sensitive species even 11 3 A.argyrophyila,A.baileyanapurpurea,A.burkittii,A.calamifolta
though the amount ofiron added to 11 10
A florabunda, A. iteaphylta, A. menzelii, A. mlcrocarpa,
the mix would be ample for many A.papyrocarpa, A.paradoxa, A. rigens, A. rivalis, A. rotundifolia,
other plants. A. sclerophylla, B. aculeata, B. larlcina, B. speciosa, G. intricate,
Response of 61 species G. robus(a, H. suberea
A. cyclops, A. fimbriate, A. hakeoides, A. longifolia sopherae,
>20 14
In a firstexperiment, seedlings of61 A. melanoxylon, A. nyssophylla, A. pendula, A. ramulosa,
species of native plants were grown H. muelleriana
in a pinebark/peat/sand (6:3:1) mix A. longifolia, A. saligna, A. truncata, A. victoriae, H. leucoptera
>20 >25
amended with five levels of single
superphosphate and sufficient iron growth.was unaffected by any ofthe ed first in the oldest pinnate leaves
sulfate to give approximately 19 or and were typical of P toxicity.
34 ppm iron in a DTPA extract. treFatomlieanrtssy.mptoms in Acacia appear Symptoms in Banksia, Grevillea and*
Additions to this particular mix
were about 0.2 and 0.6kg/mJ of
ferrous sulfate, respectively.Organic
materials differ in their ability to GRAFTED CONIFERS
'fix' added iron, so the amount of
ferrous sulfate needed to give an For The Wholesale GROWER
adequate concentration ofavailable
iron will vary from mix to mix. Over 30 varieties of Grafted Conifers
The lower concentration is on the
available this coming season
borderline of deficiency for a wide
range ofplants and 34ppm would be including —
ample for the vast majority ofplants • Cupressus Greenstead Magnificent
grown in Australian nurseries. Visual
• Cupressus Conybearii
symptoms were noted over periods
• Cupressus Raywoods Weeper
up to 18 weeks.
• Cupressus Canneys Gold
Plant responses • Cupressus Cashmeriana
Ageneral response was thatincreas • A number of Juniper standards also available
ing additions ofsuperphosphate pro
• Cedrus Atlantica and Cedrus Deodar
duced increasingly severe symptoms
of phosphorus toxicity and/or iron Cultivars available in limited numbers only
deficiency. ADVANCE ORDERS ESSENTIAL
Another general response was that
symptoms ofboth phosphorus toxic
Contact usfora current catalogue
ity and iron deficiency were less at
thehigher rateofiron addition than ^lenleigh
at the lower.
Germination percentageandinitial
Wholesale Nurseries
Lot 3R Mulgoa Road,Regentville 2745
Kenn"-'HantUeck:'w;.'a' researcher with the
. PH: (047) 33 3243 FAX: [phone]
Udelmde.:^.^.^..^/-^--.--*
B.ir*»-';(cid:127),-'*"**•*
25
Australian Horticulture, June 1991
^rMearqh
?>'(cid:127) aTv
Wy&
mixes — undrained so that none of
Hakea appearedonlyintheyoungest
the P* added was lost by leaching.
leaves during the relatively short
Leaf symptoms were noted as they
duration of this experiment and
appeared and the quality of the
were typical of iron deficiency.
seedlings was assessed at harvest.
Table 1 lists the 61 species in
The leavesand stems were analysed
Qpotswood groups according to severity of
symptoms, showing a wide range in for P and iron.
foldings si sensitivity to P in soil-less mixes.
Symptoms
An increase of iron reduced the
By harvest, the seedlings ranged in
I I (Inc.lnVktotiJl severity of the effect of P. Results
quality from dark greenand vigorous
obtained with Banksia ericifolia sug
atthe highest levels ofiron addition,
gest that even higher concentrations
combined with nil or the lowest
of iron would further reduce the
levels of P addition, to stunted and
BULK P0H1NG
adverse effects of P. almost totally defoliated at the
This experiment is reported in
lowest iron levels, combined with
more detail in the 'Proceedings of
the highest P levels.
M1XSUPPL1ERS the International Plant Propagators' An example of. the response is
Society', Vol. 40 (1990), to be
given in Table 2.
published towards the end of 1991.
Plants of acceptable commercial
quality were produced only in mixes
Response of Banksia
which had at least 1.5kg/mJ
• House plant growers ericifolia
FeS04-7H20 or215g/mJ FeEDDHA
The interaction between P and iron
• Native plant growers added and whose DTPA extracts
was studied in more detail using
contained less than 3ppm P.
• Ornamental growers Banksia ericifolia. Plants of the very highest quality
Seedlings were grown in a were only produced in mixes giving
pinebark/peat (7:3) potting mix
• Tube&Speedling less than 2ppm P in a DTPA
amended with eight levels of single
growers superphosphate in the range 0 to extract.
For this particular soil-less mix,
444g/m\ the maximum addition of single
We will formulate to Each level received an amount ot superphosphate that still allowed
ferrous (iron) sulfate (FeS047H20)
your requirements. production of high-quality plants
in the range 0 to 3kg/mJ or Librel
was 15g/m3 (equivalent to single
FeHi (Fe EDDHA chelate) in the
superphosphate at 170g/mJ).
We have standard range 0 to 430g/mJ. All mixes had
A fascinating thing about this
house mixes both soil their pH values adjusted into the
species is that its seedlings were
range 5.6 to 6.
and soil-less types. excellent in mixes with no P, so
Levels of available P and iron
long as enough iron had been
were determined by extracting the
media with dilute DTPA. added.
This 'living on the smell of an oil
Theseedlings were grown for 14
rag' behaviour is explained in part
weeks in undrained tubes of the
6 King Street,
Yarra Glen
Table 2
3775 Effect of Pand ferrous sulfate onthequality-score of B. ericifolia
Phone [phone]
seedlings, expressed as a %of maximum possible score.
Fax[phone]
FeSO«.7H20 added P added
(g/m* medium)
(kg/m' medium)
10 15 20 25 30 40
YP.aOr.raBoGxle4n5,93775 011.7..055 789432Cba 789413cba 697050cca 687053cacdb 367946dcce 457775dcbdec 456369dccde 346892ddcdee
2.0 91a 95a 91a 87ab 78bc 84b 80c 65c
3.0 96a 95a 93a 96a 88ab 90a 90a 81b
V.IU« lollow«d by th« «m. I.tl.r.r. not .Ignlflcntly dW.r.nt ,1 P-0.05
Australian Horticulture, June 1991
26
r^^-^^^-^^-^^-^—Jtf^M;t="^"«iJ^r#s srj^rwSiftf.iit^inc-;*-iv
RESEARCH
by the very high concentration of P sensitive to phosphorus should be be no more than 150g/mJ single
in the seeds — 1.3% P. This is very well supplied with iron. superphosphate.
enough to supply the seedlingsfor at Some pinebark-based mixes need Analysis of the mix before potting
least the first couple of months of ferrous sulfate (FeS04-7H20) at will soon show whether a problem is
growth. 1.5kg/mJor FeEDDHA at 215g/m3. likely and therefore could prevent
Another reason is that the proteoid Peat and sawdustTbased mixes may costly losses which could occur
root clusters formed on its roots are need less than this. later. O
super-efficient at extracting P from The most sensitive native plants
the growing medium. do not need any more P than is
Wexi;,-mantkWKevin Handrcck will l*>ok£at
These clusters excrete chemicals already present in mix components. iJfeanei^Q^ourcesffor^uon-tnejfKientjpUuitJi
that dissolve P from the solid Forothers,additionsshouldgenerally i i in 11 n^MEi'lii i \\ n "'^'iVlE'flll
particles of the medium and also
help transport it back to the roots
(see references).
In this experiment, the bark and
peat together contained 0.023%total
P, and while most of this was
unavailable to 'ordinary' plants that
do notproduceproteoid rootclusters,
some of it is dissolved from particles Quality Seed Australia
encircled by the clusters.
The number of proteoid root
clusters per plant was markedly
reduced byP additions that produced
toxicity symptoms.
Thus at the highest rate of iron
addition, the number of proteoid * Spring flowering varieties *
root clusters declined from 4.2 per
plant at 15g/m3 added P to 0.2 at available now!
40g/m3.
Numbers were depressed in plants
which were suffering from . iron
* Walz germination rate is *
deficiency, relative to numbers on
healthy, green plants. guaranteed!
The results indicate that high
levels of P reduced the movement of
iron into the new leaves. The P may
* Walz quality makes you profits *
also have interfered with the use in
the leaves of the iron that did reach
them.
Perhaps of more importance to
nurserymen was the finding that Mr Ernst Walz, of Walz Germany, welcomes all
large applications of iron reduced
existing and new customers to contact his newly
the movement of P into the leaves
appointed Australian representatives:
and so reduced symptoms of P
toxicity and iron deficiency.
Walz, one of Europes leading seed Merchants,
In other words, to some extent,
iron protected the plant from P now introduces for distribution its 1991 catalogue.
toxicity. Iron cannot prevent toxicity
from large applications of P, but it
can overcome or prevent toxicity Walz Australia
from P concentrations that are a
little above that needed for good P.O. Box 5579 439 Pine Ridge Road
growth. Gold Coast Mail Centre Runaway Bay
Application to the Qld 4217 Qld 4216
nursery industry
Phone [phone] Fax [phone]
Potting mixes for plants that are
Australian Horticulture, June 1991 27
eye
„^, - e-op,, r«pE£-J st-r£"sS;f (cid:127) -",ht cs'80'5
impact on the sale ofpotting mixes,
In recent years there hast been
talked with peat, suppliers and but not on the operations of com
increasing agitation to have the
users at a conference, 'Horticul
mining of bogs stopped, or at mercial nurseries.
tural Substrates and their Analy In Ireland (Eire), the Bord Na
least severely restricted. This agi
sis', held on Guernsey in September Mona — the government instru
tation has been particularly vigorous
mentality responsible for all peat
last year. in Germany and the UK, but
I came home with a general mining for fuel or horticulture —
impression that peat supplies are Ireland has not been immune. has responded to agitation by des
-Forexample, intheUKgardeners
secure for at least the next 20 ignating quite a few areas to be
are beine urged not to buy potting
years, and probably for alot longer. permanently excluded from mining.
composts (their term for potting
But it all depends on the amount There is still ample peat winnable-
mixes) that contain peat, and to
of impact various-'green' groups from other areas for perhaps 100
refrain from buying plants grown
have in, getting governments to years at current rates of mining.'
in peat-based media. Apparently
restrict the mining of the remaining German production of peat has.
Ihis campaign has had considerable
peat bogs. not changed from approximately
20 million cubic metres per year.
ODMMENTAL WOVEN WIDE At that rate there is enough peat
left for perhaps 100 years, if the ;
mining companies continue to have '
access to the bogs.
From the nursery point of view,
the most pessimistic forecasts are
that restrictions on the mining of (cid:127)
peat might well see curtailment;of
supply 10 to 20 years fronr now.
There are still ample supplies
available from Sweden and Finland,
and I seemed to get the impression
that the areas of peat bogs were
so large that" even considerable
restriction on activity-would not
have an impact on supply for
many decades.
A major concern, however, is
that restrictions will inevitably in
crease the price of the peat that is
mined. This plus the high cost of
transport, and the threat ofdeclining
supply from some parts of Europe
has led to interests in 'peat substi
tutes'.
In Australia now we hardly ever
talk about peat substitutes as it is
a long time since our media were
based on peat.
[phone]
Australian Horticulture. February 1991
16
Thus there is a considerable easily allowed for. It is also possible was a material for mixes that
amount of activity in assessing the with an aged bark, although rather would provide good structure for
use of other, materials such as more difficult for some plants (for at least 12 months. Our best bark
pine bark and composts made from example, seedlings). mixes easily achieve that.
sewage sludges and municipal solid The disease-suppressive properties That thought leads me to ramble
wastes. In Germany, the Peat Re of media based on composts are a little further and to state my
search Institute has changed its
in contrast to the often disease- belief that it is essential for the
name to the Peat and Humus conducive nature of peats — par least-hassle production of nursery (cid:127)
Research Institute, to reflect its in ticularly the black, more highly plants in Australia that our finite
volvement with other types of or decomposed ones. supplies of pine barks should be -
ganic materials. Much bark is used One of the most frustrating things wherever possible reserved for pot
in France and in countries such as about high-peat mixes is the large ting mixes.
Poland, but high levelsof manganese amount of shrinkage they suffer as There are alternatives for general
in somebarks from northern Europe they get dry. garden mulches and -for fuel in
limit- its use in ' horticultural Under total environmental control factories.
substrates. in Dutch or Danish greenhouses Our bark is too valuable to be
Israel finds itself in the same they work very well indeed, but in squandered for these purposes.
boat as wedo in Australia: imported my opinion they are much less But whatever happens with bark *-,
peat is very expensive. They have suitable for many of our outdoor or peat, it is likely that increasing
developed mixtures based on crushed growing conditions. amounts ofcomposts produced from
rock (tuff — similar to the scoria Several European extension other 'wastes' will have to be used
found in Victoria) and composted workers indicated that what they in the formulation of potting mixes "
wastes from cattle .feedlots and needed more than .anything else both here and overseas. O
urban waste streams. \ .
One conclusion I, have reached
Drive to green industrial wastelands
is that for many decades it will be
possible to obtain peat from Europe,
A government-backed partner- .from the government-backed Na-
albeit at ever increasing cost. Con ship between British industry ture Conservancy Council (NCC)
sidered along with the peat that
and environmental bodies is to and local consultants. It has
enters Australia from New Zealand be expanded following asuccessful created wildlife habitats and help-
and now from Asiatic Russia, and pilot project in Cleveland, north- ed investing companies prepare
local supplies from Tasmania and east-England. ecological plans.
NSW, supplies to those who want Chemical, power anrj metal in- Asa result, a reclaimedmudflat
to use, peat seem assured. dustries in Cleveland have devel- now attracts birds, seals and
:' oped an environmental improve- wildfldwers, while a weathered
Local mixes superior
rrient strategy . through the slag heap from a steelworks pro-
Yet another conclusion is that when Cleveland Industry and Conser- vides the substrate for plants
I compare our best pine bark- ,V.;vation Association (INCA), es- such as sea lavender,
'tabhshed in June 1989 with rep- The INCA, which received some
based mixes with European peat
resentatives of local authorities public funding from the NCC,
mixes, I mostly find our mixes to
and conservation bodies. has'had many visitors including'
be superior in many aspects. Sure,
With two full-time staff, the some from Eastern Europe, which
barks chew up a bit of nitrogen,
INCA draws upon expert advice has huge environmental problems.
but with a composted bark that is
Australian Horticulture. February 1991
17
"waweii(cid:127) j11lj,1Ijuwj»_i4—jbu
**-"(cid:127)*-=ri!*«j«i)'S;
,>' :#'r, * **.
Effective iron sources for
iron-inefficient plants
Kevin Handreck, FAIH
lined with a polythene bag to
amounts of phosphorus — single
In the first article in this series prevent. drainage. One germinated
superphosphate at rates of 110, 220
(AH June *91) I showed that
seedof B.ericifolia wasplanted into
and 440g/mJ mix — thereby placing
increasing the iron content of
each tube. Watering was with
soil-less potting media for native even more strain on the iron sources.
deionised water, except that about
plants 'sensitive to phosphorus can The rates of addition of the iron
sourcesencompassed therangesspeci each three.weeksadilute phosphorus-
reduce or prevent theadverse effects
fied by suppliers. Results for only free nutrient solution was used.
oftoomuch phosphorus. Ironsulfate
the highest livel of iron at the The plants were allowed to grow
and iron EDDHA were used in
middle rate of phosphorus addition for 16 weeks, at which time they
those experiments. were assessed for severity of iron
are shown in Table 1. All mixes
This article gives the conclusions
deficiency symptoms. Scoring was
of an experiment which compared were adjusted to pH 5.8.
from 0 for dead plants to' 10 for
The mixes were filled inta plastic
the ability of 22 different iron
tubes (Victorian Forestry Pots), each vigorous, completely green plants..
sources to supply iron to Banksia
ericifolia. Table 1 : Quality score of Banksia ericifolia as affected by
This plant has difficulty ingetting
various iron sources.
iron from soil-lessmedia. I usedit as
a test plant sothat I could place the iron source % Fe Rate Fe in Plant
maximum strain on the iron sources. (kg/nV) DTPA score
If they could supply iron to this extract
plant, they should be able to supply (ppm)
it to any plant likely to be grown in
Ferrous sulfate 20 1.5 42 9.0
nurseries. Dried ferrous sulfate 36.8 0.82 34 8.8
Osmocote ferrous sulfate' 28 1.08 38 10
Iron sources Micromax' 12 1.0 29 .1-5
The iron sources assessed .can be Micro Mix' 12 1.0 24 1.8
placed in one of three categories — Tracer. 5 1.0 11 0.3
iron sulfate based, iron minerals and Bar-Min-EI' 6 1.0 vrf' 0.0
iron chelates. The sources tested are Shirleys Trace Element Mixture 6 2.1 27 3.0
listed in Table 1. GU-49 from the USA , 71 1.5 40 10
.The various iron sources were GU-49 produced in Australia' 71 1.5 29 10
mixed at three rates into a GU-53' 40 1.5 25 6.0
pinebark/peat (7:3) mix that had Magnetite trom Queensland 66 1.5 9 0.2
been supplied with all othernutrients - Bayterrox 318' 65 1.5 5 0
in adequate concentrations. FTE WM25S 12 0.6 7 0
Pinebark 'ties-up' more iron than FTE 503P 16 0.6 6 0
peat does, so this mix had a high Vermiculite 4 20% 6 0.3
ability to remove the added iron Ironite' 4.5 4.5 13 3.0
from the reach of plant roots. FeEDTA in powder form 12 0.9 39
Trace elements other than iron Osmocote coated FeEDTA prills' 10 1.2 28 10
were not included in mixes that were Librel FeHi 6 0.4 9 9.7
Seqestrene 138 6.5 0.4 8 10
to receive the trace element mixtures. Fe lignosulfonate' 10.5 0.9 27 7.0
As was shown in the first article,
' Grace Sierra Chemicals; ' Kendon Chemical Co, Melbourne; ' Barnes McGrath,
Banksia ericifolia could have been
Brisbane- ' Australian Master Builders Co. Sydney: ' Ability Building Chemicals.
grown in the mix without added
Melbourne; • Bayer Chemical Co; ' Ironite Products Co, Arizona; 1 Chemical
phosphorus. However, asphosphorus
Recovery Co, Adelaide.
interferes with the use of iron by this
-All plants died (see text).
plant, it was decided to add small
Australian Horticulture. July 1991
26
Uli
> . RESEARCH
j.'
Symptoms
Iron deficiencysymptoms — yellow Table 2 t Minimum rates of application (kg/m* mix) of sources of
ing of the youngest leaves at shoot Iron suitable for Iron-Inefficient plants that are sensitive to
tips — began to appear from five
phosphorus.
weeks after transplanting. By seven
weeks many plants in mixes contain
Iron source Very low phosphorus Low phosphorui
ing the poorest sources of iron were
in medium In medium
totally yellow or dead.
The iron deficiency symptoms Ferrous sulfate 1.5 2
increased in severity as the level of Ferrous sulfate, dried 0.8 1.1
QU-49 (Australian)
phosphorus in the mix increased. 0.75 1.5
The highest level of added phos Osmocote ferrous sulfate 0.4 1.1
phorus caused death of the oldest Librel FeHi 0.2 0.3
leaves of plants in mixes containing FeEDTA <0.3 0.3
Sequestrene 138 0.2 0.2
the poorest sources of iron. Some
Osmocote FeEDTA <0.4 0.4
plants in mixes containing fairly
good iron sources lost some old
would not have helped the test the young seedlings, but plants in
leaves yet had green shoot tips.
plant. In fact, &t the highest rate mix containing 0.3kg/mJ scored 10.
Iron in DTPA extracts used, FTE 503P!provided a level of The lignosulfonate chelate was
boron that would have been toxic to inferior to the EDTA and EDDHA
Amongst the iron- sulfate sources,
sensitive plants such as violets. chelates when incorporated into the
only those giving at least 34ppm
EDTA and EDDHA chelates of mix, but it wassuperior (morerapid'
iron in a DTPA extract produced
iron produced vigorouslygreenplants greening, less burning of foliage)
vigorously green plants (Table 1).
at quite low rates of application. when they were applied as sprays
The results for Micromax and
Micro Mix show just how inefficient The highest rate of FeEDTA powder containing lg/L to iron-deficient
are plants such as B. ericifolia in application was excessive and killed plants. |»*
extracting iron from soil-less media.
One gram per litre of either of
these trace element mixtures provides
an ample supply of iron to a wide
range of plants grown in Australian
nurseries, yet plants such as B.
ericifolia need considerably more.
No doubthigherratesofMicromax
and Micro Mix would haveproduced
high-scoring plants, but the same
cannot be said for Tracel and Bar-
Min-El. Already at the highest rate
used, the concentration of manganese
in the mix was in the range known
to produce toxicity symptoms in
some plants.
The proportion of iron in these
mixtures is too low for the general
range of non-peat mixes used in
Australia.
Results for the mineral sources
show that only two — the GU-49
preparations — were able to supply
KENNY LANE
enough iron at the rates used.
An increased rate of application
of GU53 may have produced green IMPORT PTY. LTD.
plants, but the Queensland magnetite, Specialist importersofwidevarietyofbulbs forcut flowersand
Bayferrox 318 and the fritted trace potculture. All underquarantine regulations.
element preparations were extremely
P.O. Box 179, Monbulk3793, KennyLane, Monbulk,3793
poor sources of iron.
Fax: [phone] Tel: [phone]
Increasing their rate of application
Australian Horticulture. July 199I
27