IJERD – International Journal of Environmental and Rural Development (2015) 6-2

Research article
erd

Impacts of Atmospheric Temperature - Humidity Changes onYield Quality of Thai Soybean Cultivar
KANITA THANACHAROENCHANAPHAS*
Naresuan University, Phitsanulok, Thailand
Email: kanitat@nu.ac.th

OROSE RUGCHATI
Naresuan University, Phitsanulok, Thailand
Received 12 December 2014

Accepted 11 September 2015(*Corresponding Author)

Abstract This study aimed to assess the impact of atmospheric temperature and humidity
change on yield of Thai soybean, Chiang Mai 60 cultivar. The research experiment wasconducted during July - October 2013 at Naresuan University Crops Field, Phitsanulok,
Thailand. Soybean seed Chiang Mai 60 cultivars were planted in 16 open top chambers (OTCs)
under 4 different temperature and humidity levels. The four simulated climate change situations
in OTCs were, lower than ambient temperature, higher than ambient temperature, combined
elevated temperature and high humidity and ambient temperature level, which all werecontrolled by an electrical system. Results indicated that yield loss by statistical significanceoccurred in all Low-level temperature treatment (25r2.9 ๐C), High-level temperature treatment(37r2.2๐C), and high Temperature-humidity (36r2.8๐C/ 81.7r2.2%), compared with ambientlevel temperature treatment (31r1.7๐C). Exposure to simulated climate change situation in Lowlevel temperature treatment obviously reduced total pod/plant and total seed/plant by 40.8% and48.5%, respectively. High-level temperature caused yield loss in total pods/plant and totalseeds/plant by 35.6% and 39.5%, respectively. The combined effect of high temperature andhumidity on soybean crop reduced total pods/plant and total seeds/plant about 36.4% and 47%,
respectively. Finally, low temperature evidently increased in lipid content and all types of fatty
acid in experiment, whereas the high temperature treatment could reduce the total monounsaturated fatty acids. It was concluded that temperature change situations at above and lower
than ambient level in growing season could induce yield loss and some fatty acid in Thaisoybean, Chiang Mai 60.

Keywords temperature change, Thai soybean, open top chamber, yield quality
INTRODUCTION
Climate change and variability can have significant impacted on phenology, physiological mechanisms,growth, nutritional value, genetics, and yield of crops (Bainy et al., 2008; Thanacharoenchanaphas andRugchati, 2011). The “Fifth Assessment Report of the Intergovernmental Panel on Climate Change(IPCC)” conclude that by 2081–2100, the globally averaged surface temperature will be in the range of2.6-4.8 ◦C in comparison with 1986–2005 and, daily and seasonal high temperature extremes over mostland areas will be more frequent in the future (IPCC, 2013). These changes and variability in climate
may have significant impacts on yield of crops in various regions of the world (Smit and Yunlong,1996; Kumagai and Sameshima, 2014).
Soybean is one of the important C3 plants that is sensitive to temperature change (Newman et al.,2011). On the basis of long-term field experiments (1987–2007) in northeastern China, Zheng et al.,(2009) reported that soybean seed yield was increased by 6–10% per 1 ◦C rise in mean daily maximum
temperature during seed filling. Thailand Department of Meteorology reported that the annual meanⒸISERD115

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temperature in Thailand rose by approximately one degree Celsius from 1981 to 2007. By 2050, themean daily maximum temperature in Thailand will have been increased by 1.2 to 1.9 ◦C (Marks, 2011).
Hence, current mean temperature during the soybean growing season in Thailand has been changed at
meteorological observatories in the northern regions of Thailand. Based on these facts, wehypothesized that the increase/decrease in temperature and humidity during growing season haveeffects on soybean production. Our data clearly demonstrate the differences in soybean yield responses
to the change of temperature – humidity.
OBJECTIVE
This study was set to investigate the differences in Thai soybean yield responses to the changes oftemperature – humidity during growing season.
METHODOLOGY
Field Study and Experimental Design
The field study was carried out at Naresuan University in northern Thailand. The experiment was done
at agricultural crops field in the university. It is located at coordinates 16 degrees and 44.003 minutes
north of the equator, and 100 degrees and 11.810 minutes east of Prime Meridian. The total study area
covered about 300 m2.
Thai Soybean (Glycine max (L.) Merr.) Chiang Mai 60 cultivar was selected for the study; thiscultivar was widely cultivated in northern Thailand. It was planted in growing season of Thailand
during July 2013 to October 2013. Four replications of a Randomized Complete Block Design (RCBD)
were used in four treatments with four different levels of air temperature and relative humidity. At thevegetative growth stage, the soybeans in all four treatments were exposed to temperature-humidity
variability for 8 hr exposure (9.00 am – 5.00 pm) in open top chambers until harvest.
Temperature - Humidity Control
The square open top chamber was used throughout the study period. The chamber size was 1.5 m(width) x 3 m (length) x 2.5 m (height). It was constructed out of transparent plastic. There were foursituations of air temperature-humidity change, at an ambient level (AT-treatment or control treatment),
combination of low temperature and humidity at ambient level (LT-treatment), combination of hightemperature and humidity at ambient level (HT-treatment), and combination of high temperature andhigh humidity (HHT-treatment). These were controlled by an electronic system. The high temperatureand low temperature system was set up by green lighting and air conditioning exposure, whereas theelevated humidity treatments were set up by electronic water spray. Mean air temperature /humidity
levels ( ± S.D) for 8 hr for each treatment were 25r2.9 ๐C / 62 ± 9.8 % in LT-treatment, 31r1.7 ๐C/ 63± 7.4 % in AT-treatment, 37 r 2.2 ๐C/ 61 ± 5.7 % in HT-treatment, and 36r2.8 ๐C/81.7r2.2% in HHTtreatment, respectively.
Yield Quality Determination
Soybean seeds were harvested from the experimental field at maturing stage (95 days). Yield quality
was analyzed by determination in yield quantity and nutrition value (lipid and fatty acid content).
These samples were determined by number of pods/plant, number of seeds/plant and weight of 100
seeds. Lipid content and some important fatty acids were determined by gas chromatography (GC)based on analysis of nutrition content by AOAC (1995) method to estimate grain quality.
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Statistical Analysis
The experiment was designed as Randomized Complete Block Design (RCBD) with 4 replications.
Data of yield and fatty acids content were statistically analyzed by the analysis of variance (ANOVA).
Significant differences of parameters were reported at p<0.05 by DMRT.
RESULTS AND DISCUSSION
Yield Quantity
Seed yields were harvested at maturing stage. The yield component, including number of pods/plant,
number of seeds/pod and weight of 100 seeds were determined to assess grain quantity. The results areshown in Fig. 1a - Fig.1b. The significant reductions were found in all 3 parameters of yieldcomponent. The significant reductions in number of pods/plant and number of seeds/plant appeared in
LT treatment, HHT treatment, and HT treatment when compared to control treatment. Exposure toLow-level temperature treatment obviously reduced total pods/plant and total seeds/plant incomparison with control by 40.8% and 48.5%.
We also found that the cumulative effects of high-level temperature caused yield loss in total
pods/plant and total seeds/plant by 35.6% and 39.5%, respectively. The combined effect of hightemperature and humidity on soybean crop reduced total pods/plant and total seeds/plant by 36.4% and47%, respectively. The results obviously showed that high level of temperature (plus ambienthumidity) reduced the 100 seeds weight when compared to the others (Fig. 2). These results indicatedthat the higher temperature level and the lower temperature level (above ambient level) in growing
season induced high suppression in yield Chiang Mai 60 cultivar soybean.

abFig. 1 (a) Effects of different air temperature – humidity levels on number of pod/plant ofsoybean, Chiang Mai 60 cultivar and (b) Effects of different air temperature –humidity
levels on number of seed /plant of soybean, Chiang Mai 60 cultivar

Note: The different letters for each treatment indicate a significant difference at Ud0.05. Error bars above eachhistogram indicated standard deviations (S.D.) observed from samples of each treatment.

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IJERD – International Journal of Environmental and Rural Development (2015) 6-2Fig. 2 Effects of different air temperature – humidity levels on 100 seed weight of soybean,
Chiang Mai 60 cultivar

Note: The different letters for each treatment indicate a significant difference at Ud0.05. Error bars above eachhistogram indicated standard deviations (S.D.) observed from samples of each treatment.

Nutrition Value in Lipid and Fatty Acid Content
Exposure of soybeans to different air temperature-humidity levels was carried out in an open topchamber. In Table 1, we observed that the LT treatment (at lower temperature level than ambient level)
induced high lipid content in the full maturing stage (R8). However, there were no significantly
different results found in HT treatment (higher temperature level than ambient level). The significantly
different results were also clearly shown in total saturated fatty acids (TSFA), total mono-unsaturated
fatty acids (TMUFA), and total poly-unsaturated fatty acid (TPUFA). The results showed the mostobvious effects of increasing air temperature (HT treatment) led to the reduction in fatty acid whencompared with others. In contrast, the interested results showed that the low temperature treatment (LTtreatment) in growing season (than ambient level) led to the significant increase in all 3 types of fatty
acid (Table 1).
Table 1 Summary of the results of Lipid content, TSFA, TMUFA and TPUFA of soybean seed,Chiang Mai 60 cultivar grown under four temperature treatments (LT, CT, HHT andHT) in this study
Lipid andFatty acid

4 treatments under different air temperature levels
LTCT

21.5 r 0.3 b2815.7 r 24.3 c4680.7 r 45.8 c11697.9r 67.6 b

19.9 r 0.4 a2547.6 r 18.5 a4498.1 r 64.3 b11257.8 r 61.3 aHHT19.8 r 0.1 a2592.8 r 25.5 ab4753.7 r 26.5 c11195.0 r 78.4 a
Note: The different letters for each treatment indicate a significant difference at Ud0.05.
Lipid content (g)TSFA(mg/100g)
TMUFA (mg/100g)
TPUFA (mg/100g)

HT19.6 r0 0.2 a2621.2 r 34.2 b
4414.8 r 24.8 a11237.2 r 87.9 a

Many researches that have been investigated for decades showed similar results as this study. For
example, Hatfield et al., (2011) predicted that a 0.8 ◦C temperature rise would cause a 2.4% decline insoybean yield in southern USA (current growing season temperature of 26.7◦C). Numerous studies
have carried out to understand biochemical reaction taking place in plant’s physiology under climate
factors change, leading to the inhibition of photosynthesis and yield production. Its photosynthesis isvery sensitive to ratio of CO2 to O2 in the atmosphere. Increasing in this ratio of CO2 to O2 leads toⒸISERD118

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higher rates of photosynthesis (Newman et al., 2011). However, the reaction of photosynthesis isdisrupted at high temperatures and inhibit CO2 fixation (Araus and Slafer, 2011). One of the mosttemperature-sensitive reactions of carbon assimilation is rubisco activase. Rubisco activase activity is
exceptionally sensitive to thermal denaturation. Hence inhibition of the activase at high temperature
prevents activation of rubisco in leaves suffering heat stress and leads to inhibition of CO2 fixation(Crafts-Brandner and Sulvucci, 2000; Salvucci et al., 2001). Heat stress is a serious threat to crop
production worldwide. High leaf temperatures reduce plant growth and limit crop yields. Estimates
range up to a 17% decrease in yield for each degree Celsius increasing in average growing season
temperature (Lobell and Asner, 2003).
CONCLUSION
The results from the experiment showed that Thai soybeans, Chiang Mai 60 were grown undertemperature-humidity change and revealed that exposure to high temperature, low temperature, andcombination of high temperature-humidity during growing period led to the significant and obvious
reduction in yield quantity. Even though low temperature evidently increased in lipid content and alltype of fatty acid in experiment, the high temperature treatments could also reduce total monounsaturated fatty acids (TMUFA).
ACKNOWLEDGEMENTS
The authors thank Naresuan University, Thailand for the funding. This work was also financially
supported by Center for Agricultural Biotechnology, Faculty of Agriculture, Natural Resources andEnvironment, Naresuan University. We also thank to Office of Agricultural Research andDevelopment, Phitsanulok for soybean seeds, Chiang Mai 60 cultivar.
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