ISSN:
1573-5036
Keywords:
climate change
;
drainage
;
evapotranspiration
;
grassland
;
Lolium perenne
;
water deficit
;
yield
Source:
Springer Online Journal Archives 1860-2000
Topics:
Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
Notes:
Abstract Perennial ryegrass swards were grown in large containers on a soil, at two N fertilizer supplies, and were exposed over two years in highly ventilated plastic tunnels to elevated (700 μL L-1 [CO2]) or ambient atmospheric CO2 concentration at outdoor temperature and to a 3°C increase in air temperature in elevated CO2. These swards were either fully irrigated (kept at field capacity) in each climatic condition (W+), or received the same amount of water in the three climate treatments (W-). In the latter case, the irrigation was adjusted to obtain a soil water deficit during summer and drainage in winter. Using a lysimeter approach, the evapotranspiration, the soil water balance, the productivity (dry-matter yield) and the water use efficiency of the grass swards were measured. During both years, elevated CO2 increased the annual above-ground drymatter yield of the W- swards, by 19% at N- and by 14% at N+. Elevated CO2 modified yield to a variable extent during the growing season: a small, and sometime not significant effect (+6%, on average) was obtained in spring and in autumn, while the summer growth response was stronger (+48%, on average). In elevated CO2, the temperature increase effect on the annual above-ground dry-matter yield was not significant, due to a gain in dry-matter yield in spring and in autumn which was compensated for by a lower summer productivity. Elevated CO2 slightly reduced the evapotranspiration during the growing season and increased drainage by 9% during winter. A supplemental 3°C in elevated CO2 reduced the drainage by 29–34%, whereas the evapotranspiration was increased by 8 and 63% during the growing season and in winter, respectively. During the growing season, the soil moisture content at W- and at the high N supply declined gradually in the control climate, down to 20–30% of the water holding capacity at the last cut (September) before rewatering. This decline was partly alleviated under elevated CO2 in 1993, but not in 1994, and was enhanced at +3°C in elevated CO2. The water use efficiency of the grass sward increased in elevated CO2, on average, by 17 to 30% with no significant interaction with N supply or with the soil water deficit. The temperature increase effect on the annual mean of the water use efficiency was not significant. Highly significant multiple regression models show that elevated CO2 effect on the dry-matter yield increased with air temperatures above 14.5°C and was promoted by a larger soil moisture in elevated compared to ambient CO2. The rate of change in relative dry-matter yield at +3°C in elevated CO2 became negative for air temperatures above 18.5°C and was reduced by a lower soil moisture at the increased air temperature. Therefore, the altered climatic conditions acted both directly on the productivity and on the water use of the grass swards and, indirectly, through changes in the soil moisture content.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00010998
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