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Title Applications of Quality Control to Liquid Feeding Systems and
Testing of Peat Soil in Glasshouse

Author(s) Gormley, T. R. (Thomas Ronan)

Publication 1972
Date

Publisher International Society for Horticultural Science

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The importance of peat ~s a growing medium for glassh~use ~r~ps is : ..

well known. It is a standard medium to which all nutrients must be added

and has excellent water holdi)lg capacity..Tomatoes are often grown in ,- ' i!
15-20 <;m of peat (shallow trou11h method) and conside)'.'able qualitities of

-~-water and liquid feed are applied during the grCJWing season; <)Specially

at times.when there is a heavy demand because, of good light conditions. : .\':···· '!
It is eas;jr, therefore, to underfeed or overfeed planti;; .~pecia,lly ,si1).c;e . ,. ,... ·

the dept]j' of Peat is so s mall aqn~daltihtiys could a ffect yield advers{)ly:. In• a1-i : : '. •J \
dition, nutri tion affe,cts fr\iit so .it i s also
imp9rtant to e)lsu:re > • •· ·

thhathall p_fantsj,et tfh!_,~ame amtount of feed in ordterTtoh: mahintain unifot:m •· . •.·.... :?.:(ii

1 1ig .qua1ity. v,v!'r ecumg pan .s .a so raises cos s .... ew o 1e oper_a.ion:: ·;,, .. ,:;,

>of feediirg; watering ancl soil tef'!ting is similar to a m;oduction line in · · ; .·· ·· •&
amneY'thm."~a"ns~'a·.·ct·u.·).·'·~.··'·ing ·i·)'ldus' tr'y·anq..),.en·d· s·. itself readily to;.q u· a·l.i· t.y·,g· o· n t r·p ·"·i' . '' . · ·/ :, ,.,i.?
.
Quantity off~ed andJrrigation wat~r ·~··~··:·.~'. ,\) }/c•<·~·J<\~~\\

. .. . .·.·. .·.·. ... ..
.· The qua)ltiti~s cifJ'j3~ and i;r~gittion water required by pl?,nts vary '
•J
considerably with light conilitlohs..'j'ranspiration rateiiJollo"'. solar ra~ V : . • ii
iS_ Pre~b_ly that delri_and for nu~xiep.ti{ _fo_l_~- ·:.~::_·:.-/::~-
diatiOn levels _plosel;V__and-it -_-(:_,-_::-;_ ·01
·

1lows a similaJli'.E,t,1~~rn. The data iri figure 1 show fluctuationfs in sqil crn1-: ' F.·•.'.:.:.
ductivity (SC, . . ) eve1s, measured at weekly interva1s, or spring · .. :... ~.;
crop tomatoes gtOwn in:-peal_J'Jie plants in the experiment were.fed and •. ·.,,··

. wita_ter~d .at diffferentthrates deflpentdint!". on d_ay 1Cengtb.th an~~wtheatther co11ditions. :/ .. ·.i.
c is oov1ous_ _rom. e 1arge uc ua ions in 8 _o a1nt.!Ll a.: -some m_ore -·'"f; ~,
ohbjectivefcontrol is rtequirhed. This"ii~chievedfhood1H:rfrigati~rt.byt...·• ) · ii~
t e use o. a so1arime er, owever, good objective met s .or estu:rta !i!~lRt.•"/. ·. ·
amounts.· of feed required are not yet available and s.ciil analytical data. ;,<
···.··.·.:;•_;._:.·
·. the main index, It is possible, therefore, that the fluetuations obSE!rveq . " " ·.
in figure 1 would have beE!n.much less had the pfants been fed al)dwa~ere.<l' •·! ·( .·.;~
· · .· · .· · . t .. / ·\ o t·
using objective control. . .

Checking dilutes . .· · .. . . . . • · . . ·., . . .· ·•.• ) ; . · ·, ·· '~•

Dilut.,,rs should be checked every time that feeding is being carried Qut · · >

to ensure that they are working properly. Growers with a centraloc)il~fing ·\~
plant \Vi}l probably havfil. an SC n:ieter built. into the system and the xead~ ·

ings shouli! be checked daily. In the case of the smaller type of diluters

the setting on the head is ofteri difficult to adjust. SC vafoes for stock ·.·

sol\ltions. of commercially available feeding mixtures at vario.us dilution ·

rates are given in table 1. The SC value for the c)iluting water is added

to the figure in the table and the results written in the bracketed space.

· · In this way, growers can make a modified versfon of the table for the.ir

own use thus ensuring quality control of the feed. If Jhe reading is not .·

179.

~Ji:/·:· - ' . ·: ,.. !.,'•·, - . ' . ·, .' _, -

· col'.rect th~,; tnore 0r iess diiutingwater qan be .used as requfr<)d, The'

SC test, therefore, .serves to check that the stock solution has been cor-

recil:Y prepared and. thatthe diluter isoperating correctly, The praGtice

of adding the SC of the· diluting water. to the figures in table 1 gives a

1 <•I.\~;;;>>
good approximation of the correct SC for the diluted feed provided the

SC of the diluting water is not too high 80 (table 2). •

Most instruction.sheets supplied with diluters recommend thaUhe rate
I.·.·.'.•'.:· of water flow into the diluter should be checked each time feeding is car-

r· ' .I ried out, Thi,s is to ensure that the correct amount of feed is applied if

F'· ·· ·· a timing method is used. For example, a mairui flow rate of 1580 L/hr

gives a flow :rate from the ·diluter of 1188 L/hr and a mains rate of 2500
,, . . , L/hr gives a diluter rate of 1443 L/hr (table 3). If feeding, therefore, is

T ·. ·· ' carried out for. 1 hour the· amount of feed applied could vary if the flow

\ rate. is not checked. The diluter, however, reduces the effect of different
I . flow rates, i. e,.. a difference in mains flow rate of 920 L/hr (2500-1580)

I·: tois reduced 255 L/hr (1443-1188) by the diluter. The rate of dilution

I.·. was. independent of the ·flow rate of .water into the diluter in the case of
i~ev~;~ f~~oe,:;~;t~\::~~a1:t~t~~e ~~ei~~~:1fed ~n~~~ek~&t~~b~~:sed.1.i.·•.·..··._·.·;.,.·.·•···..•·.·.·.·.·•.•.· .· ·. Diff~rencesJn flow.rates from the mains are not now "reduced'' by th.e
''' scihsetcokemd.eaIstusrheo.quuldanbteitpieosinctoeudl0dubt~thvae~r'ymeucrrhoo-f ·

'.·,.·.•.·.· '·. dnIeHoi1lster'iaf nfldPu\Ys1r1a1tgeas time ba
are not
!','·•' · this data willnot apply if a grower has his own water supply and pumping

'·,1.•• .••.:,•·.•_.•·•.·'•..·,·.•·.• ·.• ·.·.·.·.•·_..'.· Asyssvte,rmveys.inocfew:;oantelyr v,,eurpyplsielisg.hutsevdarbiyatgioronws einrsflcoawrrriaetdesouwtoiunld19b6e9·;e.j<shpoecwteedd.

1 ··that 'I.bout 30% of Irish growers obtained their supply frbm mains.. Flue-

,·.·.····.· tuatipns in flow rat.es for mains water at Kinsealy at different times of I
;- , .the day. a.nd different days of the week, are presimted in table 4. Flow
L
[J.':': ·•·· rates. varied considerably on Mondays.

1·. · These. data indicate, therefore, that measuring flow rS,.tes shol)ld en-

[". . sure more uniform feeding and irrigation.

r·

I' Control of feeding systems

Plants in glasshouses are usually fed by hose, low level sprayline or

trickle systems., As already mentioned, if feeding or irrigation is being

done by hose; the quantities applied can be measured reasonably accu-

i . rately provi<fed flow rates 'are known. In the case of trickle a bottle is

! · usually placed under. one drip and the quantity applied is measured in

thisway, This, however, assumes that each drip is delivering at t'he
same ra1;e. While, it 'i~.Jinpractical to measure the delivery,•rat<l from
eac1It,rickl,e,• if is, il~sirable to make spot /lleastirem!)nts to find how well··
the ~yijtem is working.• The ,results (table,lifshowfh(l delivery 'i;a,tes .·
f):om two trickle systems (one adjustableJ~Iid a sprayline sy$tein.' Each.

system was checked'at the.middle (three adjacent nozzles) and qoth ends ·

(three ai!jacent no.zzjes). Delivery rates varied most in ~he trick!e sys-

tem.· Delivery rate&iwere lowerin the centre for the non-adjustable
trickle systel)i and ~he sprayline system. Rate of delivery from'.spray-

lines,)l'as measured by placing a polythene cowl over the nozzle ,aµd col-
.fecting the water ih a flat container. In the case of adjustable trickle .

systein, ,nozzies should be inspected daily and spot delivery checks taken. ·

lSO

- - _:.,;.__

::.··.•n-:;f\'·;?~'.::~:.:-~;::;:; - ·-:-- -- ~-:,.------------ -,-- --- · ·· -··: ;'.:-· -· -;---,-,_-·' · .-,-- ·····"'~--:-:'!'!•·•· ..•, .•·•- •·:r::>;,c-r00·:;
! - -'' . '

:

'

It -

Soil analysis

I. If feecling andirrigation has been carried out correctly",

L• soil analysis should be necessary. In general, _results for . .

I. - are sufficient. Occasionally, results may be required which ne~

I cessitates doing the analysis on a wet sample. Accurate cari be ..
obtained provided the operator realises the need for extra care when-fil~
I
ling the measuring container with wet peat (table 6). Sieving the wet
I
sample also poses problems. ·
!
Sampling plans and calculation of standard deviations are of great im-
I
. portance during the base fertilisation of peat in bulk. The bulk sample-
; ! . ./
can be subsampled thoroughly and the subsamples analysed. Th<l stari- ·
I
dard d(lVcJ~tlon can be calculated rapidly by the range method,. '\'IJ.is>i:iives/'
'
an indication of the mixing method and allows different methpds to _be·
1r
compared. ._ · _ . · _ _ ._ . _._ • ·__ · ,·__·
. \".i Attim~s it may al130 be necessary. to obtain soil analytical,tesµlts of a

j( desired precision aµd a problem arises concerning th!" numliei:"o{sa!Ilples

11 liewhich, sho11ld ):>e analysed to get(! _result within the d<i~ired liriHts. This
I11'
I)lay foiportl;lnt when buying f!"rtilised peat in bulk inorder'to deter-
tl
mine Uthe required amount of fertiliser, e. g. NPK,' has b".en added to
I
the peat. If the mixing methods are good, it is simple.to (lstimate Uie -·_
i
amount since t)le _results for .each subsample tested will be. al{outthe · ·
I,1'
same. However, if results from different subsamples vary a lot, indica-
ii
ting bad mixing, then it is more difficult to obtain an average_figure and
i
equation I must be used to obtain the number of samples to be-analysed ··
:1
in order to get the true fertiliser content· within certain limits. ·
:1
r~----- · (ks)_ 2 n= number of samples required.
'I: n
= s= standard deviation ·
:I · e· e= desired precision

l k= 1. 95 for 95% assurance _._ . , . .

!! ' A large number of replicate samples can be taken and the standard devF .

i ation calculated for any or all of the factors to be measured,' e. 'g. pH, K;

I SC. The figure for the desired precision (e) is entered in the equation ·

and the number of samples to be ana).ysed to obtain results of a des ire<l

precision calculated.

Analytical service . .. . .· · ... . · :_-..

Sorneof the above tests can be done readily by the growt'lr himseU, e:g.

SC measurements of feeds and_s.oils. However, it is.also impoi:-tant to.

have a rapid analytical service to assist the grower and carry out s'oIIle

of the more difficult tests. Using quality control methods; it is possible,·

therefore, to feed and irrigate soils more uniformly' ensure Uniform

base fertilisatfon of peat and obtain produce which Will be of uniform . . -

quality. More rigid control of feeding methods _should result in economy ·

and saving in relation to cost of feed. ··

Summary
Glasshouse crops are often grown in shallow depths of peat.- Carefuf

control of base fertilisation, liquid feeding and irrigation is essential
for top quality. This "industrial process" lends itself readily to quality
.. control methods.

'.181

i'',.,

l!ltt'
r•

1::·;;~

)',(> The soiarimeter gives an index of the amount of irrigation required,

· '[j~'·'"i· · but water flow rates from the supply mains are important since quanti-
ties of feed and water applied are often measured on a time basis.

I .. Diluters and stock solutions can be checked by comparing specific con-

1 ductivity (SC)readings on feed with figures in a table:

·t'IQ<'.·j . Delivery rates from hose, iow level sprayline and trickle systems

s~h£iosu1l:d:ia1:l s.ovebs e,tht eeslteeadsft raemq uoeunntt loyf and indic.ations are that the sprayline
variation from region to region along

'.F' ·., ·. ··Ii' Soils should be analysed on a routine basis for pH, K and ·SC. Special
attention must be given to uniformity of base dressing in peat and proper
., :. ··~' sampling m.,thods enable different mixing techniques to be compared,

1 •, Much of the testing can be done by the grower himself, however, it "'·.-. ,
1
~u~~~~~~~~:;t:::::r::~o:~.::u::;::::~t~:::~c:~ringe~ .
1.··.·.·.·············.·.·.•.·•·. ·.·, Mllchtigkeit gezogen; Sorgfaltige DurchfUhrung von GrunddUngurig, fllis-
. 1,'· "::.· .H
.siger.Nachdiingung und Bewlisserung sind fiir die Erzeugung best<lr
I1;f"..•L•> ·.·i ,.
Qualitat unbedingt erforderlich. Regelmlissige.vorzunehmende Kqntrol-
;
. len bieten hierbei eine Moglichkeit zur Qualitlitssicherung. · I

Der Solarimeter liefert zwar ein Mass fiir die erforderliche Hohe I

'• der Bewasserung, aber es ist wichtig, die Zuflussgeschwindigkeit zu I·

\ . kennen, da DUnger- und Wasserm<)ngen sehr oft auf Zeitbasis gemessen I

I · w.erden. Verdiinnungsmittel und StammlOsungen konnen iiberwacht '

I' W<lrden, indem man die ermittelte 'Spezifische Leitflihiglteit der Diinger- I'

I lOsung init Tabellenwerteri vergleicht.
Die Durchflussgeschwindigkeit der Bewasserungsschlauche, am

JI Boden verleger SprUhschlauche und von Tropfchenbewlisserungssystemen

sollte ebenfalls haufig iiberpriift werden. Es ist bekannt, dass der

1 Spriihschlauch von Abschnitt zu Abschnitt a:uf der gani::en Lange die ge-

l&/ ) ri':~:# ~~rtt~~~':.,1f:e~'::i~;uf pH, K Utjd. spezifis6he Leitf'ahigkeit .

' I < ' '"' unter~ucht werden, In Torf ist der gleichnilis'.sigenA~ngµhg der
GrunddUpgung bese>nd.~.re Bea()htung zu sch,f'/Jkeri..·Bei tichtiger Probe-
: entna,hlne kapn man v~rschiedene Mischtechriiken vergleichen, . · '

!1Y •: ' · .Vi.,le dieser Prilfungen kllnnen von Glirt'}er selbst durchgefiihrt\ver-

v
f : . .. den, ·ein guter "Analysen-Seririce" ist aber,.trotzdem wichtig. · . \

If! >
l:

·]!

"'

182

r:c'.·>:'._·~-~:>~··:.:.-1·i;·'.-:.~\-i..·~;·:;:~>-~---'~'..~:_''..:.~-~~~;~~·'.:·~:~:.:i;(;;~·;~ ~;~·-~---~::_:,:_:::__,__ .~_ .~"-~,-~:_jf(, ·:____:~·-:~ ~~: .~·-·-- ·

~'-' Uqu id feed

+;-'i.-- Water

280 l per plant

240

200
u
l/) 160

0

l/) 120

80
·40

2 4 6 8 10 . 12 14 16

Time (weeks)
Figure 1 - Fluctuation in soil SC readings.

I
I

i. ~·Table '1 · SC (jf stopk solution.s at various dilutions in distilled water.
l1'.t0},.;···.

r11t:\:";

1 ··· ···. sto~ks~lution Dilution rate
111
I;; " ;.· .

100 150 200

--~~~--"-~~~~--'~~~~~~~~~~~~'--~~~~~~·

I . . . .I 681 g kNo 3, + o.gJ · ··
·· 141 g) urea
· 180 ( 122 ( 94 (

454 g)

['. .. Product x No.. 1 152 ( ) 105 ( ) 78 ( ) .I
128 ( ) 87 ( ) )
I 2 115 ( ) 78 ( ) 67 ( ) .
. 43 ·80 ( ) 55 ( ) 59 ( )
·..· 138 ( ) 95 ( ) 42 ( ) l
5 211 ( ) 72 ( )
I. , ... ' ·... 6 ) 149 ( ). 114 ( ) .I
34 ( 17 (
.7 ..25 l ) '!
. .• . .•. . .·. .
; . .. . ·.·

.Table 2 - SC of sto.cl<: solutiOn diluted 1. in150 with distilled :,;atkr arid

· ·with four.other water supplies. · · ·

SC of water SC of feed .SC of fe"'d
supply . by addition
obtained in practice
14 13.7 (123 + 14) ,•
25 148 (123 + 25)
40 163 (123 + 40) 141
82 . 205 (123 + 82) 146
0 (dist. water) 158
195
123

:;-_<. ·Table 3 - Change in SC of feed coming from diluter (fixed setting) fed
· · with water at difJ;erent flow rates.
r

j'"',;'·'.,-.: '

t

how rate at tap SC of feed coming 'Flow rate
,,· l/hr · from diluter at EX diluter
fixed setting
- ·l l/lir
110
• 1580. 1188 .
170
. 1810 170 1277
2040 170 1342
2270 170 1360
2500 1443

. 184

· Tab1ei p:i~6w rat~ (l/hr) ~iik~n~ealy wat~riiia111S•~&~;ly~ii0Kf; '
·•• ·;r!dif;ferenttimes mrtl),reedifferentdays_. •;! )
0
I'
.Time of day. '' Day
i ' Wednesday
Monday
I
10. 00 hr 2520 2690 2620
I 12. 00 hr 2620 2520 2690
14. 00 hr 1940 2585 2520
! 16. 00 hr 1940 2340 2485

! Table 5 ~ Delivery rates (ml/minj fro:ri: diffe~ent fE1eding sy~t~T~
measured at both endsl and m the centrel). .. ·. .. .• · ·· · "·
·I .
·~
/
. ' ' ._ -.,._ - - ~ ' - :
i
'Location ! Feeding system
/[ Sprayline3) .'·.-T;iJk1e3>•
'i'rickle2>
·I···
p;)ld}' 10. 5,' 530
i ·centre 500
'8. i ' 517
' En:d 2
9.3
'l
i 1) figures are means for three drips or nozzles

i 2) non-adjustable trickle · ·

·i 3) low level sprayline

4) adjustable trickle

Table 6 - Mean analytical figures for 50 glasshouse soil~ befo;e 1~nd
after. drying.· ·· ·

Before dryin~l After dryingb) . sti t test

pH c) 6. 390' 6.434 +0. 0.16 · N"'S
301 302 +2. 04
K (ppm) +o. 53 NS ·
SC 96 95

a) moisture· contents varied between 3. 7 and 73. 2% • .· ·...·. , ·. · · ·"

b) air~dtj.i;ci at 15°C for 12 to 24 hr , ·. · . · ..

c) pH values for advisory purposes are normally read to one de'cimal .
place ·· ·

185