Limited research has been conducted and uncertainty exists regarding sugarcane response to
water stress during different development phases. This information is necessary to optimize
the allocation of limited irrigation water for sugarcane production. The objective of this study
was to understand and quantify the response of crop water use (CWU), canopy development,
stalk elongation, biomass accumulation and partitioning, and sugarcane yield to mild water
stress, imposed through deficit drip irrigation, during different development phases.
A field experiment consisting of a plant and first ratoon crop of cultivar N49 was conducted
near Komatipoort. For the three water stress treatments, available soil water (ASW) was
maintained between 30 and 60% of capacity during the tillering phase (TP), stalk elongation
phase (SEP) and through both phases. ASW was maintained above 60% of capacity in the
well-watered control and during periods when stress was not intended.
Rainfall prevented water stress from developing in the TP of the plant crop. In the ratoon
crop, 72% less irrigation was applied in the TP, resulting in 50 days of stress (ASW<50%).
This did not affect stalk population but reduced CWU by 13%, shortened stalks by 21% and
affected the canopy by reducing green leaf number (GLN) and green leaf area index (GLAI).
Relieving the stress during SEP allowed the crop to re-establish its canopy, capture adequate
photosynthetically active radiation (PAR) and restore rates of photo-assimilation (as
suggested by CWU) and stalk elongation to support rapid biomass production. This
restoration of plant processes allowed the ratoon crop to attain a cane and stalk dry biomass
(SDM) yield that was only 9 and 11% lower (statistically insignificant), respectively, than the
well-watered control at lodging (crop age of 286 days).
During the SEP of the plant and ratoon crop, 42 and 85% less irrigation was applied, resulting
in the crops experiencing 74 and 39 days of stress and using 7 and 8% less water,
respectively. This did not affect stalk population or the crop canopy, but reduced stalk height
by about 6 and 14% in the plant and ratoon crops, respectively. In both crops, shorter stalks
and a negatively affected CWU which reduced photo-assimilate production, reduced cane
yield by 14 and 10% (statically insignificant) and SDM yield by 15 and 5% (statistically
insignificant), in the plant and ratoon crops respectively.
© University of Pretoria
iv
Deficit irrigation throughout the TP and SEP of the ratoon crop reduced irrigation amount by
74%, resulting in 110 days of stress and reducing CWU by 16% and stalk height by 14%.
PAR capture was reduced through reduced GLAI. This resulted in a significant reduction of
15% in cane yield. SDM yield was reduced by 17%, although this was not statistically
significant.
Stalk sucrose content was not influenced by deficit irrigation but was rather dependent on the duration of the drying-off period prior to harvest. Sucrose yields were therefore largely
determined by SDM.
Results suggest that the soil water potential (SWP) measured at 0.25 and 0.40 m depths,
halfway between drip emitters within a plant or ratoon crop, can drop to about -40 kPa before
irrigation is applied, without sacrificing cane or sucrose yield. Lastly, a ratoon crop can
rapidly recover from stress during the TP, provided that the SWP during SEP is maintained
above -40 kPa. / Dissertation (MSc Agric)--University of Pretoria, 2013. / gm2014 / Plant Production and Soil Science / unrestricted
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:up/oai:repository.up.ac.za:2263/40346 |
| Date | January 2013 |
| Creators | Rossler, Ryan Louis |
| Contributors | Singels, Abraham, ryanrossler11@gmail.com, Steyn, J.M. (Joachim Marthinus), 1963- |
| Publisher | University of Pretoria |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Dissertation |
| Rights | © 2013 University of Pretoria. All rights reserved. The copyright in this work vests in the University of Pretoria. No part of this work may be reproduced or transmitted in any form or by any means, without the prior written permission of the University of Pretoria. |
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