Thesis (PhD(Agric) (Agronomy))--University of Stellenbosch, 2003. / 108 leaves printed on single pages, preliminary pages i-vi and numbered pages 1-1 to 1-5 to 9-1 to 9-3. Includes bibliography, list of abbreviations and 22 figures in color. Digitized at 300 dpi grayscale and 300 dpi 24-bit Color to pdf format (OCR), using an HP Scanjet 8250 Scanner. / ENGLISH ABSTRACT: A long term experiment was conducted at the Langgewens Experimental Farm, near Malmesbury in the Western Cape province of the Republic of South Africa. The
effect of soil tillage, crop rotation and nitrogen fertiliser rates on mineral-N levels in
the soil, nitrogen levels in plants, wheat growth and yield components, grain yield as
well as quality parameters of spring wheat were determined.
Although the tillage treatments tested were initiated in 1976, present crop rotations
and nitrogen application rates were only applied since 1990. Most of the data that are
discussed however was recorded during the 1997 to 2001 period.
The trial was designed as a randomised complete block with a split-plot arrangement
and four replicates. Main plots were tillage methods namely conventional tillage
(CT), tine tillage (TT), minimum tillage (MT) and no tillage (NT). Crop rotations
used were continuous wheat (WW) and wheatl lupin/wheat/canola (WLWC). Both soil and crop data were
recorded.
The results of this study showed the differences in total mineral-N content of the soil.
N-contents of wheat, wheat growth and yield components as well as wheat quality
parameters were found between tillage treatments, crop rotations used as well as N-
fertiliser rates applied. Response however, varied largely between years due to annual
variation in especially total precipitation and distribution of rainfall. The inclusion of
a legume crop (lupin) and canola in the rotation with wheat was found to have only a
small effect probably due to the fact that lupins were grown once in a four year cycle
only.
Application of different nitrogen rates did increase the mineral-N in the soil, but the
effect did not last very long in most years due to either N-leaching or plant uptake. To
ensure sufficient mineral-N levels, late application of N-fertiliser will therefore be
needed. Minimum tillage or reduced tillage performs better than conventional tillage
in low rainfall years. In general these tillage systems should be combined with crop
rotation to ensure that yields are comparable to that obtained with conventional
tillage. / AFRIKAANSE OPSOMMING:
Die ontwikkeling, graanopbrengs en bakkwaliteit van koring (Tritium aestivum L.) in reaksie
teenoor gewasratasie, metode van grondbewerking en N-bemestingspeil is in 'n lang tennyn
sllldie op Langgewens Proefplaas, naby Malmesbury in die Weskaap provinsie van die
Republiek van Suid-Afrika, bepaal.
Hoewel die verskillende grand bewcrkingsmetodes sedert 1976, en gewasrotasies en
slikstofpeile sedert 1990 toegepas is, is daar in hierdie studie gekonsentreer op data wal
gcdurcnde die periode 1997-2001 ingesamel is.
Die eksperiment is as 'n randomiseerde blok ontwerp met vier bewerkingsmetodes nl.
konvcnsionele bewerking (CT), tand bewerking (TT). minimum bewerking (MT) en geen
bewerking (NT), twee gewasratasies nl. monokuhuur koring (WW) en
koring/lupienelkoringiCanola (WLWC) en drie N-peie (60 kg N ha- ', 100 kg N ha- 1
, 140 kg N
ha- I uitgevoer. Aile stikstof is in die vorm van kalksteen-ammoniumnitraat toegedien.
Die reaksie van beide grondfaktore soos die minerale N inhoud en gewaskomponente 5005
biomassa produksie, opbrengs en kwaliteit teenoor bogenoemde faktore het '0 goeie
korrelasie getoon met die heersende klimaatstoestande.
Lae reenval jare (gebiede) sal volgens hierdie stlldie die grootste voordeel verkry met minder
intensiewe grand bewerkingstelsels. terwyl 'n frekwensie van meer as een peulgewas per
siklus van 4 jaar nodig sal wees om grondvrllgbaarhcidsvlakke betekenisvol te verhoog.
Stelsels van rninder intensiewe grondbewerking is ook tot 'n grater mate deur gewaswisseling
bevoordeel as konvensionele melOdes van grondbewerking.
Hocwel minerale-N vlakke in grond deur verskillende N-peile be'lnvloed is, was die
efTektiwiteit van toedienings laag en het verdeelde tocdienings groat voordele ingehou.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/949 |
| Date | 03 1900 |
| Creators | Maali, Safiah Hasan |
| Contributors | Agenbag, G. A., University of Stellenbosch. Faculty of Agrisciences. Dept. of Agronomy. |
| Publisher | Stellenbosch : University of Stellenbosch |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | 1 v. (various foliations) : ill. |
| Rights | University of Stellenbosch |
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