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Saturday, May 11, 2019

Manderscheid et al. (2018) -- Positive Influence of Elevated CO2 on Wheat

"Nitrogen supply - 
A determinant in 
water use efficiency 
of winter wheat grown 
under free air 
CO2 enrichment."

Manderscheid, R., Dier, M., 
Erbs, M., Sickora, J. and 
Weigel, H.-J. 


Water Management 
210: 70-77.

In a field study 
over two 
growing seasons, 
Manderscheid et al. (2018) 
examined the 
combined effects 
of elevated CO2 
and nitrogen supply 
on winter wheat 
(Triticum aestivum, cv Batis) 
at the Th√ľnen-Institute 
in Braunschweig, Germany, 
in 2014 and 2015.

Elevated CO2 will 
increase wheat yields 
in the future, 
while requiring 
less total water
than at present,
to do so. 

Elevated CO2 levels 
wheat biomass, 
among the three 
different levels
of nitrogen supply
and across years; 
averaged across 
both growing seasons.

A +207 ppm 
CO2 enrichment 
increased biomass 
production by 17%, 18% 
and 15% in the deficient, 
adequate and excessive 
nitrogen supply treatments, 

Nitrogen supply had 
a positive effect 
on the aboveground
biomass of wheat.

Plant water use efficiency (WUE) 
was also strongly influenced 
by soil nitrogen levels and 
atmospheric CO2 enrichment.

Focusing on CO2, 
data averaged 
for both seasons 
indicated a 
CO2-induced WUE increase 
of approximately 21% in the 
nitrogen-deficient treatment 
and 30% under both adequate 
and excessive soil nitrogen. 

The positive effects 
of elevated CO2 
on biomass and WUE 
resulted in 
an overall reduction 
of evapotranspiration 
(sort of like people sweating)
by 2, 9 and 10 percent 
in the deficient, adequate 
and excessive soil nitrogen 
supply treatments, 

Manderscheid et al. 
conclude that
 "the decrease 
of evapotranspiration 
suggests that 
seasonal water use 
of well-fertilized wheat 
will improve 
under elevated CO2."

Two atmospheric 
CO2 concentrations 
(ambient, at 393 ppm, 
or elevated, at 600 ppm) 
and three levels of soil nitrogen 
(deficient, adequate or excessive, 
accomplished by adding 40, 180 
or 320 kg N ha-1, respectively, 
in 2014 and 35, 200 
and 320 kg N ha-1 in 2015). 

Elevated CO2 levels were maintained 
using free-air CO2 enrichment (FACE) 
technology; but the CO2 enrichment 
was only applied during daylight hours 
from the three leaf stage until the end 
of grain filling (i.e., harvest) 
in each growing season. 

Irrigation was also applied, as needed, 
by the authors to maintain the soil water 
capacity within 50-90% of field capacity 
to prevent drought and nitrate leaching.