Thesis (MScAgric)--University of Stellenbosch, 2001. / ENGLISH ABSTRACT: The aim of this study was to determine the effect of a grass herbicide, a
broadleaf herbicide with some grass control capabilities, method of tillage (tine
and no-tillage) at planting of wheat as well as different medic cultivars on the
regeneration, dry matter (OM) production and quality of a medic pasture.
The trial was conducted at Langgewens experimental farm in the Swartland
wheat producing area. Nine medic cultivars of three different species were
evaluated after being sprayed with either haloxyfop-R-methyl (HAL) ester or
imazamox (IMI) and subjected to either a tine tillage or a no tillage treatment at
planting of wheat. Soil samples were taken during January 2000 to determine the
size of the medic and weed seedbank as well as the degree of dormancy in the
medic seeds, while OM samples were taken throughout the growing season to
determine the OM production of the different medic cultivars and weed species.
OM samples taken during October 1998 on the same pasture, were used to
determine the crude protein (CP) and neutral detergent fibre (NOF) content of the
pasture. The samples were subjected to in vitro digestion and the digestibility of
pasture CP (OCP), NOF(ONOF) and DM (DOM)were determined.
Results showed that seedling establishment differed between cultivars used,
herbicide treatments applied as well as the crop stage in the rotation. The
cultivars produced more seedlings where IMI was applied compared to HAL as
well as where the area consisted of two year pasture compared to one year
pasture (1998) and one year wheat (1999). After a year of pasture and a year of
wheat, cultivars Sephi and Paraggio produced the most seedlings, while Caliph
and Orion produced the least. Caliph however, showed a very high degree of
seed dormancy while Orion's low seedling establishment was due to its
sensitivity to the IMI herbicide used.
Little difference was found between the nine cultivars early in the season (July -
August) with regard to cumulative OM production, except for Orion, whose
growth was severely damaged by the IMI treatment. At the end of the growing
season (October), the cultivar Caliph's cumulative OM production (2010.1 kg/ha) was significantly higher than all the other cultivars, except for Parabinga (1053. 4
kg/ha).
Oifferent pasture samples, of which the botanical composition was known, was
analysed for CP, NOF, OOM, OCP and ONOF. There was no significant
difference in pasture composition during 1998 but variation in the pasture
composition did however cause the IMI treatment, compared to the HAL
treatment, to have a lower ONOFand OOMcontent. A modelling procedure was
used to predict the pasture quality parameters (CP, NOF, OOM,OCP and ONOF)
from the pasture composition (medic hay, medic pods, grassy and broadleaf
weeds). This prediction of CP, NOF, OOM, ONOF and OCP from the pasture
components had a relative low accuracy (49 -74.1 %) and a further refinement of
this model for possible use on farms in order to improve grazing management
and animal production is advised.
In conclusion it could be said that broadleaf weed control caused a definite
increase in medic seed and OMproduction, but Orion should not be used with an
IMI herbicide. All the cultivars, except for Orion, produced enough seedlings up
to the second year to ensure sustainability of the medic pasture. All the cultivars,
except for Orion, produced a sufficient amount of OM early in the growing
season. Caliph however, produced by far the most OM later in the growing
season.
A reduction of broadleaf weeds and medic pods will increase the digestibility of
NOFand OMand therefore increase the quality of the pasture. Pods however are
an important part of summer forage and the aim should therefore rather be to
reduce the number of broadleaf weeds in the pasture. / AFRIKAANSE OPSOMMING: Die doel van hierdie studie was om die effek van 'n gras en breëblaar
onkruiddoder (wat sekere grasse beheer), metode van bewerking tydens die saai
van koring asook nege verskillende medic kultivars op die regenerasie, droë
materiaal produksie en kwaliteit van medic weidings te bepaal.
Die proef is gedoen op Langgewens proefplaas wat geleë is in die Swartland
koring produserende gebied. Nege medic kultivars is geëvalueer nadat die
weiding met of haloxyfop-R-metiel ester (HAL) of imazamox (IMI) onkruiddoders
gespuit is en onderwerp is aan of 'n vlak tand of geen bewerking tydens die saai
van koring. Grondmonsters is geneem in Januarie 2000 om die grootte van die
medic en onkruid saadbank asook om die graad van dormansie in die
verskillende medic kultivars se sade te bepaal. Droë materiaal monsters is
gedurende die 2000 groeiseisoen geneem om die droë materiaal produksie van
die verskillende medic kultivars asook onkruid spesies te bepaal. Droë materiaal
monsters is gedurende Oktober 1998 geneem en gebruik om die ruproteïn (CP)
en neutraaloplosbare vesel (NDF) inhoud van die weiding te bepaal. Die
monsters is in vitro verteer en die verteerbaarheid van CP (OCP), NDF (ONOF)
en droë materiaal (DOM) is bepaal.
Resultate wys dat saailing vestiging verskil tussen die verskillende kultivars wat
gebruik is, verskillende onkruiddoder behandelings asook die stadium van die
weidings/koring. Die kultivars het meer geproduseer waar die weiding met IMI
behandel is in vergelyking met waar HAL toegedien is, asook waar koring nog
nie gesaai is nie. Na 'n jaar van weiding en 'n jaar van koring, het die kultivars
Sephi en Paraggio die meeste saailinge, en Caliph en Orion die minste saailinge
gehad. Caliph het egter 'n hoë graad van dormansie in sy saad getoon, terwyl die
swak vestiging van Orion die gevolg is van die kultivar se hoë sensitiwiteit
teenoor IMI.
Min verskil is gevind tussen die nege kultivars, vroeg in die groei seisoen (Julie -
Augustus), wat kumulatiewe droë materiaal produksie betref, behalwe vir Orion
wat erg beskadig is deur die IMI behandeling. Aan die einde van die groeiseisoen (Oktober 2000) was die kumulatiewe droë materiaal produksie van die kultivar
Caliph (2010.1 kg/ha) betekenisvol hoër as al die ander kultivars behalwe vir
Parabinga (1053.4 kg/ha).
Weidingsmonsters, waarvan die botaniese samestelling bekend was, is ontleed
vir CP, NDF, DDM, DCP en DNDF. Daar is geen betekenisvolle verskille gevind
in die botaniese samestelling van die weidingmonsters geneem in 1998 nie,maar
die variasie in botaniese samestelling het veroorsaak dat IMI in vergelyking met
HAL 'n laer DNDF and DDM inhoud het. 'n Model is opgestel wat die
weidingskomponente (medic hooi, medic peule, gras en breëblaar onkruide)
gebruik om die kwaliteits parameters (CP, NDF, DDM, DCP en DNDF) van die
weiding te skat. Hierdie skatting van CP, NDF, DDM, DCP en DNDF deur van die
weidingskomponente gebruik te maak het 'n relatiewe lae akuraatheid gehad (49
-74.1 %) en verdere verfyning van hierdie model vir moontlike gebruik op plase,
ten einde weidings bestuur en diere produksie te verbeter, word voorgestel.
Die gevolgtrekking kan gemaak word dat breëblaar onkruidbeheer 'n definitiewe
verbetering in die medic saailing en droë materiaal produksie van die medies te
weeg gebring het, maar die kultivar Orion behoort nie saam met 'n IMI gebruik te
word nie. AI die getoetste kultivars, behalwe Orion, het voldoende saad
oorlewing vertoon tot en met die tweede jaar van die rotasie om
lewensvatbaarheid van die sisteem te verseker en alle kultivars, behalwe Orion,
het voldoende droë materiaal produseer vroeg in die groeiseisoen. Caliph het
egter laat in die groeiseisoen by verre die meeste droë materiaal geproduseer.
'n Vermindering in die hoeveelheid breëblaar onkruide en peule in die weiding sal
tot 'n verhoging in die verteerbaarheid van NDF en DM lei en dus 'n verhoging in
die kwaliteit van die weiding tot gevolg hê. Peule is egter 'n belangrike bron van
voedsel aan weidende diere gedurende droë somermaande en die verbetering
van weidings moet eerder gedoen word deur te poog om breëblaar onkruide te
beheer.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/52517 |
| Date | 12 1900 |
| Creators | Beyers, Hendrik Philippus |
| Contributors | Agenbag, G. A., Ferreira, A. V., Stellenbosch University. Faculty of AgriSciences. Dept. of Plant Pathology. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | Unknown |
| Type | Thesis |
| Format | 91 p. : ill. |
| Rights | Stellenbosch University |
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