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Rice yields decline with higher night temperature
from global warming
by ;Shaobing Peng, Jianliang Huang, John E. Sheehy, Rebecca C.
Laza, Romeo M. Visperas, Xuhua Zhong,Grace S. Centeno, Gurdev S. Khush, and Kenneth G. Cassman
K.K.M.N.Chamara
AG/2008/2732
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Introduction
World rice production must increase by 1% annually to meet the growing demand for food that will result from population growth and economic development
But……
With global warming rice yield
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Crop yield crop biomass
Photosynthesis
Respiration
losses
Temperature
How temperature affect on rice yield ??
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Objectives
To determine whether there were significant time trends in changes of temperature or radiation and whether these changes had an impact on grain yield
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Materials & Methods
• Meteorological instruments
- Gunn–Bellani radiation integrator
- Solarimeter
- Glass thermometers (for minimum and maximum temperatures)
- Psychrometer
- Thermohygrograph
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• Weather Data Collection
A weather station was set up at the research farm of IRRI at lat 14°11’ N, long 121°15’ E and an elevation of 21 m
• The site measures 10.5 * 9.5 m and is surrounded by irrigated rice throughout the year
• The experimental field in which rice yields were measured was located within 1 km of the weather station
• Topography is flat
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• Measurements
- Dry- and wet-bulb temperature
- Daily minimum and maximum air temperatures
- Total radiation
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Crop Data Collection
• Field experiments were conducted at the IRRI Farm during the dry and wet seasons of 1992–2003
• To eliminate genetic factors, only crop data for IR72 were used in this study
• Seedlings were raised in trays
• 14 days old seedlings were transplanted
Dry seasons – Jan. 3 – Jan. 22
Wet seasons - June 17 - July 17
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• Hill spacing - 0.2*0.2 m, with 4 seedlings per hill
• Plot size - 5 * 6 m
• Fertilizer application
• Fields were flooded 4 days after transplanting
• Floodwater depth of 5–10 cm was maintained until 7 days before maturity
• Apply pesticides
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• Twelve hills (0.48 m2) were sampled diagonally from a 5-m2 harvest area for each replication at maturity to determine panicle number per hill, above-ground total biomass, harvest index, and yield components
• Plants were separated into straw and panicles• Straw dry weight - oven drying at 70°C • Panicles - hand-threshed• Filled spikelets were separated from unfilled
spikelets. • Three subsamples of 30-g filled spikelets and
5-g unfilled spikelets were taken to count the number of spikelets.
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• Above-ground total biomass was the summation of straw,rachis, and filled and unfilled spikelets dry matter
• Spikelets per panicle, grain-filling percentage (100 filled spikelet number/ total spikelet number), and harvest index (100 filled spikelet weight/above-ground total biomass) were calculated
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• Grain yield was determined from a 5 m2 area in each replication
• The significance of time trends in changes of
temperature and radiation was determined by testing the statistical significance of slopes at the P < 0.05 probability level according to the Student’s t test.
• The relationships between yield attributes and climatic parameters were evaluated by using correlation and partial correlation analyses
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Data analyze
• Main database management tool
- Climate Computer (CLICOM) system
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Results and Discussion
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Conclusions
• Annual mean maximum and minimum temperatures have increased by 0.35°C and 1.13°C, respectively, for the period 1979–2003
• Grain yield declined by 10% for each 1°C increase in growing-season minimum temperature in the dry season, whereas the effect of maximum temperature on crop yield was insignificant
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