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- Author or Editor: Norman J. Rosenberg x
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Abstract
The concentration of CO2 in air sampled above a sugar beet crop was measured during July, August, and early September 1966 at Scottsbluff, Nebr. During July the mean daytime concentration decreased from 310 ppm to 283 ppm as the leaf area index increased from 0.8 to 4.0. Only small deviations from the mean daytime concentration of 283 ppm occurred during the remainder of the season. The mean nocturnal concentration during this period was 320 ppm and was more variable than the daytime concentration. The daily amplitude of concentration averaged 70 ppm and was as great at times as 100 ppm.
Regression analysis revealed strong negative correlation between CO2 concentration and mean wind speed during the night. Mean concentration was independent of mean temperature, mean incident radiation, and predominant wind direction.
During each day the concentration remained constant between 1½ hr after sunrise and 1 hr before sunset except for a few cases. These were associated with incident radiation below 0.2 cal cm–2 min–1 and/or wind speeds at 25 cm above the crop of less than 0.3 m sec–1 or more than 3 m sec–1.
Evidence is presented that the concentrations reported here are at least partially dependent on the flux to and from the sugar beet crop.
Abstract
The concentration of CO2 in air sampled above a sugar beet crop was measured during July, August, and early September 1966 at Scottsbluff, Nebr. During July the mean daytime concentration decreased from 310 ppm to 283 ppm as the leaf area index increased from 0.8 to 4.0. Only small deviations from the mean daytime concentration of 283 ppm occurred during the remainder of the season. The mean nocturnal concentration during this period was 320 ppm and was more variable than the daytime concentration. The daily amplitude of concentration averaged 70 ppm and was as great at times as 100 ppm.
Regression analysis revealed strong negative correlation between CO2 concentration and mean wind speed during the night. Mean concentration was independent of mean temperature, mean incident radiation, and predominant wind direction.
During each day the concentration remained constant between 1½ hr after sunrise and 1 hr before sunset except for a few cases. These were associated with incident radiation below 0.2 cal cm–2 min–1 and/or wind speeds at 25 cm above the crop of less than 0.3 m sec–1 or more than 3 m sec–1.
Evidence is presented that the concentrations reported here are at least partially dependent on the flux to and from the sugar beet crop.
Abstract
Historical frost events (minimum shelter temperature ≤32° F.) were studied at 10 locations within and adjacent to the Platte Valley of Nebraska and the cause of these frosts was determined with the aid of synoptic maps. Frost series based upon last spring or first fall advection or radiation are defined and found to be random and normally distributed. The “potential growing season”, defined as the interval between last spring and first fall advection frosts, is found to be from 15 to 32 days longer than the “growing season” defined by the interval from last spring to first fall occurrences of minimum shelter temperature of 32° F. or below. The numbers of annual spring and fall radiation frosts and the number of days between last two spring and first two fall radiation frosts are presented to permit estimates of the practicality of frost protection for specialized crops in the area of study.
Abstract
Historical frost events (minimum shelter temperature ≤32° F.) were studied at 10 locations within and adjacent to the Platte Valley of Nebraska and the cause of these frosts was determined with the aid of synoptic maps. Frost series based upon last spring or first fall advection or radiation are defined and found to be random and normally distributed. The “potential growing season”, defined as the interval between last spring and first fall advection frosts, is found to be from 15 to 32 days longer than the “growing season” defined by the interval from last spring to first fall occurrences of minimum shelter temperature of 32° F. or below. The numbers of annual spring and fall radiation frosts and the number of days between last two spring and first two fall radiation frosts are presented to permit estimates of the practicality of frost protection for specialized crops in the area of study.
