Understanding the interactive effect of waterlogging and shade on cotton (Gossypium hirsutum L.) growth and yield Ullah Najeeb1, Michael P. Bange2,1, Brian J. Atwell3, Daniel K.Y. Tan1 1
Department of Plant and Food Sciences, Faculty of Agriculture and Environment, The University of Sydney, NSW 2006, Australia CSIRO Agriculture Flagship, Australian Cotton Research Institute, Narrabri, NSW 2390, Australia 3 Department of Biological Sciences, Faculty of Science, Macquarie University, Sydney NSW 2109 Australia
[email protected] 2
Hypothesis: Does cloudy weather intensify the negative effect of waterlogging on cotton yield? Treatments: o Waterlogging at early reproductive growth phase of cotton (81 and 77 days after sowing in 2012‐13 and 2013‐14, respectively) o Shade (No shade, 50 % shade) (6 and 9 days in 2012‐13 and 2013‐14, respectively) a day before start of waterlogging Data collection o Leaf growth, photosynthesis and N were collected from the youngest fully expanded leaves at the termination of treatment (waterlogging+shade) o Yield data were collected at crop maturity Leaf N % (relative to NWL control)
WL
WL+shade
2012-13 2013-14
15 10 5 0 -5 -10 -15 -20 -25 -30 -35
SLA (relative to NWL control)
Fig. 1 Changes in N (%) contents in cotton leaves in response to waterlogging and shade Treatments Shade
WL
WL+shade
30 25 20 15 10 5 0 -5 -10 -15 -20 -25
2012-13 2013-14
Fig. 2 Changes in specific leaf area (SLA) of cotton in response to waterlogging and shade Lint yield (relative to NWL control)
Treatments Shade 0
WL
WL+shade
2012-13 2013-14
-5 -10 -15 -20 -25 -30
Fig. 3 Changes in cotton lint yield in response to soil waterlogging and shade WL, waterlogging; WL+shade, waterlogging and shaded
Acknowledgements
Results and conclusions o Waterlogging significantly reduced specific leaf area (SLA), leaf N and photosynthesis in both years (Fig. 1 & 2), o Extended shade (9 days, 2013‐14), on the other hand, increased SLA and leaf N (%) of WL and NWL plants (Fig. 1 & 2) without increasing photosynthesis indicating that shade reduced N allocation per unit leaf area and consequently photosynthesis (Fig. 4) o Waterlogging alone caused higher yield loss (21%) in 2012‐13 than in 2013‐14 (14%) (Fig. 3) o Extended (9 days) shade caused 19% and 22% yield reduction in NWL and WL cotton, respectively, in 2013‐14 (Fig. 3), o Yield losses under combined stress factors (WL+shade) were always greater than the minor stress factor alone but the major stress factor reduced cotton yield independently of the minor stress factor (Fig 3) 40
Photosynthesis (μmol CO2 m-2 s-1)
Treatments Shade
35 30 25
y = 77.901x + 10.289 R² = 0.6083
20 15 0.15
0.20
0.25
0.30
0.35
Specific leaf N (g m-2 )
Fig. 4 Relationship between leaf photosynthesis and N concentration per unit leaf area
This project is funded by Cotton Research and Development Corporation (CRDC), Australia. Authors are thankful to the University of Sydney, Australia for a USYDIS research grant and CSIRO, and Department of Biological Sciences, Faculty of Science, Macquarie University, and Australian Cotton Research Institute, Narrabri for technical support and research facilities.
