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A GTUDY OF
A Thesis, presented in partial fulfilment of the requirements for the degree of
�aster of Agricultural Science at
�assey University
Peter James 1/civor filarch, 1971
I wish to especially thank Professor B. rt. '.:i'atkin, my
supervisor, for his helpful guidance and encouraging discussion durin3 this study.
I am grateful to others who have helpedi l.�l.� =�. F. Battersby
for willing help in the field recording, r.ir G. ;. Arnold for
statistical advice, Mr D. B. J�ond for discussion and criticism of the !ir3t draft of this thesis aucl �.:r .t. : . • :.. Leitch and the photographic department who reproduced the figures.
Finally my thanks to ?.:rs ... • Smith for her careful typing of this thesis.
;.)ection
Acknowledg1nents.
Introduction 1
Chapter I. rieview of Literpture.
.::napter -r ,. ....
Jhaptel' lii.
Chapter rv.
summary.
�ni�Dl Inta�e Hnd :electivity GrazinL �Pbaviour
:rhe Grazing .-recess
'.:he .i.'attern of.' ��efoli'-ttion /,. ��electivity
3. Frequeucy and Intensity of
3 4 6 7
�eroli�tion of individual Units 15
, .:>. ;' t.·r·i I!1Cnt "!"
..�...
... Intrc.u.uction
-:·,
t;aterials
,j).
v• ::et hods n. ?esulta
' '
�)iscussion
...
1:xpe�· irtJe n t II.
;... Introduction B. i."aterials c. kethods D. .,esul ts :t.. iiiscussion
General Discussion.
21 22 23 28 47
61 62 62 64 78 87 9?
Table
of vontents (cont'd).�)iblio2)raphy Appendix I .i-.ppendix 11 Appendix III.
Table Page
Chapter I.
1.1. rl comp�riaon of the severity of defoliation �ith stocking rate ond grazing pressure (modiried after
liodgson and 0llerenshaw, 1<)6g). 1?
�hapter II. hxperirnent I.
II .1. �,tock.ine ·:ate a 23
II.2. : ean daily �:.;rowth rato3 (kgs/ha/day) 31
II. 3. ..i.1otanical com?osi tion (.>·.� dry matter) 32
1I.4. ..ean heir;hts (nm) and green lea!'
leneths ( .:; .1 ... L.,.) of tillers (mm). 34 II.5. Til lers counts (nu�bcrs/m2) 35
Ii.6. �ean weekly loos of tillers by uprootine� .from 15 .\;Jril tu 12 _ ,a.y
(numb0rs/m2). 3�
II.?. i,iv�woi,..:ht ch�nr;ee of ewes (kt;s) 36
li.&. Grazine times (hrs/dny) 37
II. 9. .,:eaaons for loss c! tiller records,
�nd lossea in each category 38 11.10. �requency of defoliation (days
between defoliations) 39
II.11. ; ean green leaf len�th and height (cm) of grazed and ungrazed tillers
before grazin� 40
II.12. 0ubsequent defoliations of tillers
previously erazed or ungrazed 41
II.13. Heverity of defoliation of individual
tillers as length of G.L.L. (mm) and
as percentage of G.�.L. removed (�). 43 II.14 (a). Frequency of defoliation of
"old", "young" and "youngest" tillers
(days between defoliations). 44
(b). severity of defoliation of "old"•
"young" and "youngest" tillers (% G.L.L.
removed per defoliation) 44
List of Tables (cont'd).
II .15. Variati.on in some animal and pttsture
paraoeters and thoir inter-relationships 53 II.16. t,:ean G.L • .L. of ''old", "young" and "youngest"
tillern (cm). 58
.:;hapter III. �"J)erinent II.
III."�. �'ean daily GI'o·.vth rntes C�.gs/ha/day) 64
III. 2. llotanical composition (,:!1 dry matter) 68
III.3. kean heights (mm) and green leaf le��th
(G.I.L.) of tillers (mm). 68
111 .4. ·.rillers counts ( numbcr/m2) 69
III. 5. Li veweighta cl�:mr;es cf we there (j�r:s) 70
III.6. �easons for loss of tillers records, and
losses in each cate�ory 71
11:.7. �requency of defoli�tion (days between
defoliations) 71
111.8. ;,·ean �reen loa.!' len•.th �3nd h·=dt�ht (c:n) of grazed and Ulli�razed tiller::; befo:r-e
defoliation ?2
111.9. �:.ubsequent defoliations durinG period. l of tillors Grazed or uncrazod prior to
July 10. 73
111.10 • . ·'.everi ty of defoliation o.!: individual
tillers as lene;th of G.�, ... _,. (run.) nnd as
percentage of G.l.oL,. renoved (._) 73 III.11(a). l<'requency of defolinticn of "old", and
"young" tillers (days betv·een
defoliations) ?6
(b). Geverity of defoliation of "old" and
"young" tillers CJ G. L. I1. removed per
defoliation) ?6
III.12. Mean G.L.L. of "old" and "young" tillers
(cm). 83
O.F r'IGUttLS
-
�hapter I.
I.1. delation of rate of herbage intake, rate of bitinD and size of bite to
length of tiller (after nllden and
( .hititaker, 1970).
Chapter II.
11.'1.
11.2.
li.).
II.4.
.c;xperiment I.
Changes in total dry matter available (1-.gs/ha)
�hanges in mean hei�ht and green leaf lentt;th (li • .u • .U.) of sward (mm).
Geverity uf defoliation of individual tillers (A) �·;eau u. L. LJ• (mm) removed
and (B) �" G.!J.L. removed at a single defoliation
l'attern of leaf selection on tillers
Chapter Ill. Experiment II.
III.1. Changes in total dry matter available
5
28
42
42 46
(Kgs/ha) 65
111.2. �hanges in mean height and green lea!
length (G.L.L.) of sward (mm) 66
III.3. Severity of defoliation of individual
tillers (A) Mean G.L.L. (mm) removed, ?4
and (B) "/b G.L.L. ramoved at a single
defoliation 74
III.4. Pattern of leaf selection on tillers 7?
.Plate 1.
2.
4.
View of plots showing transect in
position and grouped markers beneath the transect line.
General and close-up view of the pastures prior to commencement of Experiment I.
Close-up view of the "medium stocked" and
.. high stocked" pastures at the end of ZXperiment I.
General view of aite of Lxperiment II and close-up of "merino" pasture at commence-
25
29
30
ment of grazing showing pntch grazing. 67
Development of the "dung patch" grazing effect on the "merino" pastures al'ter
3 weeks and after 6 weeks. 84
