EFFECT OF ELEVATED CARBONDIOXIDES ON GROWTH OF SOYBEAN

Soybean is a farm crop that belongs to the family of legumes. It is scientifically called (Glycine max (L) Merrill).
Soybeans are a globally important crop, providing oil and protein.(long et al.,2006 ).
It is believed that soybean has been part of the history of China for about 5,000 years, but now the production of soybean is circulating to different parts of the world
Soybean derivatives such as soy-gari, soy-milk, soy-ogi, soy-ebiripo and soy-lafun have been developed and found to be good substitutes for more conventional food ingredient like melon, cowmilk and cowpea
Over the last two centuries, accelerating rate of fossil fuel use and forest clearing human have led to increasing of carbon dioxide in the atmosphere (houghton et al. 1996)
The CO2 concentration near the ground level has risen from 280ppm in the pre-industrial time to the present 390ppm
Rising the atmospheric CO2 is arguably the most certain aspect of global atmospheric change and is expected to reach 550ppm double pre-industrial level, within this century (IPPC. 2007)
Growth at elevated [CO2 ] stimulates photosynthesis and increases Carbon supply in all C 3 species.
The ability of legumes to exchange Carbon for Nitrogen with their N 2 -fixing symbionts has led to the hypothesis that legumes will have a competitive advantage over non-leguminous species.
The potential effect of elevated CO2 on soybean have shown numerous effect on leaves, stem, and branches that, also increases carbon assimilation and plant biomass (koner 1993, rogers et al 1994, norby 1994)

Justification

Often, it is argued that Nigeria need not worried about climate change. However, Nigeria is flaring more gas than any other country in Africa: 2.5 million cubic feet per day. This actually correspond to 40% of the gas which is used in whole African (IPPC, 2007).
According to a study commissioned by the world bank in 2007, Nigeria account for roughly one-sixed of the world-wide gas flaring which in turn, spews some 400 million tons of carbon dioxide into the atmosphere.
By 2050, soybean (glycine max) will grow in an atmosphere with a 50% higher carbon dioxide concentration (CO2) (prentice et al.,2011)
Hence, there is need to elevate the growth and yield of soybean varieties under elevated CO 2 concentration in the rainforest agro-ecology of Nigeria.

Objective
To examine the effect of elevated carbon dioxide on growth, yield components and yield of some selected varieties soybean

Materials and method
Description of Experimental Site
The experiment was an on-going research carried out at the Directorate of University Farms (DUFARMS) of the Federal University of Agriculture, Abeokuta (FUNAAB), Ogun State, Nigeria. The geographical location lies in the South Western Nigeria (latitude 700 15’N, longitude 300 28’E).

Experimental Treatments and Design
The study will be a 3 x 2 factorial experiment laid out in split plot arrangement fitted into randomized complete block design (RCBD), replicated three times.
The treatments would consist of three soybean varieties (TGx 1448-2E, TGx 1440-1E and TGx 1740-2F) and two levels of carbon dioxide (ambient and elevated).

Open Top Chamber (OTC) Construction and CO2 Enrichment Treatments
Three large growth open top chambers with an internal chamber height of 2 m and growth area of 7m × 3 m each was used to represent elevated CO2 level.
The open top chamber (OTCs) was constructed using PVC pipes covered with transparent polyvinyl chloride (PVC) nylon sheet having above 90% transmittance of light. The OTCS was installed on the plots at 3WAP.
The treatments was exposed to differing levels of atmospheric CO2 (ambient and elevated) from 3 WAP to 9 WAP during the experiment using yeast produced-CO2.
Four (4) CO2 generator bottles was placed in each plot. The maximum and minimum CO2 concentration in the OTCs was measured during the enrichment period using a portable CO2 meter (NDIR Gas Analyzer (Bentech GM8883), China).
Three large growth open top chambers with an internal chamber height of 2 m and growth area of 7m × 3 m each was used to represent elevated CO2 level.
The open top chamber (OTCs) was constructed using PVC pipes covered with transparent polyvinyl chloride (PVC) nylon sheet having above 90% transmittance of light. The OTCS was installed on the plots at 3WAP.
The treatments was exposed to differing levels of atmospheric CO2 (ambient and elevated) from 3 WAP to 9 WAP during the experiment using yeast produced-CO2.
Four (4) CO2 generator bottles was placed in each plot. The maximum and minimum CO2 concentration in the OTCs was measured during the enrichment period using a portable CO2 meter (NDIR Gas Analyzer (Bentech GM8883), China).
Three large growth open top chambers with an internal chamber height of 2 m and growth area of 7m × 3 m each was used to represent elevated CO2 level.
The open top chamber (OTCs) was constructed using PVC pipes covered with transparent polyvinyl chloride (PVC) nylon sheet having above 90% transmittance of light. The OTCS was installed on the plots at 3WAP.
The treatments was exposed to differing levels of atmospheric CO2 (ambient and elevated) from 3 WAP to 9 WAP during the experiment using yeast produced-CO2.
Four (4) CO2 generator bottles was placed in each plot. The maximum and minimum CO2 concentration in the OTCs was measured during the enrichment period using a portable CO2 meter (NDIR Gas Analyzer (Bentech GM8883), China).

CO2 Gas Production

Developed an easy and cheap method to produce CO2 by using a yeast-sugar solution in plastic bottles.
40g of baker yeast was measured into a beaker, dissolved with lukewarm water for several minutes to dissolve air into the solution.
The solution was transferred into the 5 litre bottle (CO2 generator bottle). Saitoh et al., 2004
250g of sugar was measured into a large beaker, stirred gently to dissolve and poured into the CO2 generator bottle, then filled with water up to 4 liters.
The CO2 generator bottle was perforated at the top to allow small amount of dissolved O2 from their contact with the atmosphere.

Materials and methods
CULTURAL PRACTICES
Planting Operations
Two to three seeds of soybean was planted per hole at a depth of 2 cm – 5 cm at a spacing of 50 cm × 10 cm on the field and later thinned to 1 plant per stand at 2 WAS.
This will translates to five (5) rows per plot including the border row and each row would contain 21 plants. This was translate to 105 plants per plot.

Sampling and Data Collection
Data was collected on;
Growth parameters: leaf area, number of leaves, plant height, stem girth, leaf area index.
Developmental parameters: Number of days 50% flowering and number of days to harvesting
Yield parameters: number of branches per plant, number of pods per plant, number of seeds per pod, weight of pods per plant, weight of pods per plot, 100 seed weight.

Statistical Analysis
Data collected was subjected to analysis of variance (ANOVA) using the Genstat Release 12.1, (Copyright 2009, VSN International Ltd) and the differences among treatment means was separated using Least significant differences (LSD) at 5% probability level where F values are significant. The counted data was transformed using square root and the transformed data was used for statistical test. Growth parameters of soybean were subjected to repeated measures analysis of variance (ANOVA). Correlation and path analysis of regression model would also be carried out.

Reference
Chakraborty, S., Murray, G. M., Magarey, P. A., Yonow, T., Brien, R. G. O., Croft, B. J., Baebetti, M. J., Sivasithamparam, K., Old, K. M., Dudzinski, M. J., Sutherst, R. W., Penrose, L. J., Archer, C. A., and Emmett, R. W. 1998. Potential impact of climate change on plant disease of economic significance to Australia. Aust. Plant Pathol. 27:15-35
Ajay G and Arvind B. Genistein: A multipurpose isoflavone. International Journal of Green Pharmacy Year: 2009 Vol: 3 Issue: 3 Pages/record No.: 176-183. 2009.
Amadou I, Yong-Hui S, Sun J et al. Fermented Soybean Products: Some Methods, Antioxidants Compound Extraction and their Scavenging Activity. Asian Journal of Biochemistry Year: 2009 Vol: 4 Issue: 3 Pages/record No.: 68-76. 2009.
 Anderson JW and Bush HM. Soy protein effects on serum lipoproteins: a quality assessment and meta-analysis of randomized, controlled studies. J Am Coll Nutr. 2011 Apr;30(2):79-91. 2011.

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