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RESPIRATORY RELEASES OF CARBON DIOXIDE BY AERIAL PARTS AND ROOTS OF FIELD-GROWN ALFALFA AND SOYBEANS
Abstract
Measurements of dark respiration rates of full crop, soil plus roots and bare soil were made on field-grown alfalfa at Mead, Nebraska during the growing season of 1978 and in soybeans during 1979 and 1980 using an open flow chamber system. Large chambers (0.91 x 0.51 and 1.22 m high) were used to measure respiration rates of the full crop (soil + roots + aerial parts). Small chambers (0.61 x 0.41 and 0.20 m high) were used to measure respiration rates of soil plus roots and bare soil alone. Full crop respiration rate of alfalfa ranged from 278 to 855 mg CO(,2) m('-2) h('-1). The overall average alfalfa respiration rate was 531 mg CO(,2) m('-2) h('-1). Full crop respiration rate of soybeans ranged from 207 to 984 mg CO(,2) m('-2) h('-1) in 1979 and 303 to 998 mg CO(,2) m('-2) h('-1) in 1980. The overall average soybean respiration rate was 524 mg CO(,2) m('-2) h('-1) in 1979 and 627 mg CO(,2) m('-2) h('-1) in 1980. Alfalfa roots contributed most to the total CO(,2) respired by the crop (about 63%) while in soybeans, respiration of aerial parts contributed between 87 and 93% of the total CO(,2) released by the crop. The dependence of respiration on temperature in the field situation was evaluated by means of three temperature coefficients--Q(,10) (Van't Hoff's coefficient), u (Arrhenius' coefficient) and b (Belehradek's coefficient). Results were comparable with those reported for other investigations conducted but made under laboratory conditions. Respiration was reduced linearly with soil water potential less than -1.2 MPa; above -1.2 MPa full crop respiration rate was apparently unaffected by soil water potential. Seventy to 94% of the variation in full crop respiration rate was explained by variation in air temperature and soil water content. A tendency was observed for the respiration rates to increase with decreasing barometric pressure. When all deviations in barometric pressure during the period of observations were considered, no significant correlation was found. A trend was noted for an increase in wind velocity to cause an increase in crop respiration rate. The correlation between pressure difference (chamber-open air) and respiration rate was very poor.
Subject Area
Botany
Recommended Citation
DA COSTA, JOSE MARIA NOGUEIRA, "RESPIRATORY RELEASES OF CARBON DIOXIDE BY AERIAL PARTS AND ROOTS OF FIELD-GROWN ALFALFA AND SOYBEANS" (1983). ETD collection for University of Nebraska-Lincoln. AAI8423773.
https://digitalcommons.unl.edu/dissertations/AAI8423773