The main aim of this study was to determine the transpiration efficiency coefficient
(TEC) for three C3 crops; canola, wheat and lucerne. TEC relates to the efficiency of
water management in crop production. It is defined as the ratio of seed or biomass to the
product of transpiration and vapour pressure deficit. Of these variables, transpiration is
the most difficult to measure. Two experiments (canola, 2007 and wheat, 2007&2008)
were therefore designed with the aim of partitioning evapotranspiration (ET) into its
components of evaporation (E) from the soil and transpiration (T) from the plant. These
experiments were based on a split plot design, with two soils (Clovelly and Bainsvlei)
and two surface treatments which comprised of a bare soil for measuring ET and a 50
mm thick gravel mulch for measuring T using the lysimeter unit of the University of the
Free State at Kenilworth near Bloemfontein. These components were measured regularly
and E was derived by subtracting T from ET. The results showed that for canola, E was
12% of the total ET (809 mm) and for wheat E was 27% of total ET (639 mm). The
percentage contribution of T to ET was high in both crops: 718 mm or 88% of total ET of
canola and 489 mm or 63% of total ET of wheat. Conclusive evidence showed that crops
should be managed differently with respect to their individual irrigation water demands.
The remaining three experiments were dedicated to factors influencing the TEC of crops.
Specific objectives were to establish the effect of growth periods during the reproductive
stage on the TEC of canola, the effect of weather on the TEC of wheat and effect of
cutting periods on the TEC of lucerne. All experiments were conducted in the lysimeter
unit and measurements were based on the soil water balance of both soils. TEC was
expressed as grain yield (GY) or seed yield (SY), above-ground biomass (AGB) and total
biomass (TB). Soils had no significant effect on TEC. However, TEC of canola was
significantly affected by growth periods. For growth periods, TECABG varied between
3.82 and 4.95 g kPa mm-1 and TECTB between 3.94 and 5.04 g kPa mm-1. For wheat it
was concluded that weather had no influence on the TEC based on AGB, but TEC based
on GY was significantly lower in 2008 (TEC = 0.9 g kPa mm-1) compared to 2007 (TEC = 2.3 g kPa mm-1). This was caused by severe frost which occurred in the early
reproductive stage. The result revealed a mean TECAGB of 4.75 g kPa mm-1 for the two
wheat seasons. The results on lucerne suggested that cutting periods do played a
significant role in the TECAGB of the crop. TEC decreased from 3.86 g kPa mm-1 for the
first cutting period to 2.22 g kPa mm-1 for the sixth cutting period, with a mean TEC
value of 2.84 g kPa mm-1 for all six cutting periods. TEC values for canola, wheat and
lucerne in this study are consistent with values reported for other C3 crops in the semiarid
environments and are therefore recommended for use in models.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:ufs/oai:etd.uovs.ac.za:etd-10192011-135927 |
| Date | 19 October 2011 |
| Creators | Haka, Imoh Bassey Ukoh |
| Contributors | Prof CC du Preez, Prof LD van Rensburg |
| Publisher | University of the Free State |
| Source Sets | South African National ETD Portal |
| Language | en-uk |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.uovs.ac.za//theses/available/etd-10192011-135927/restricted/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to University Free State or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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