organic matter in the hardwood mulch plots as compared to the decomposed granite-based xeriscape plots. In addition, the CO2
flux seemed unaffected by fertilization/irrigation, as measured emissions did not increase beyond the baseline for any treatments including St. Augustinegrass or Sand-Capped Lawns. It should also be noted that the measured CO2
flux
reported here should not be confused with net carbon balance of a given landscape system. Tis is because the chamber used to measure gas emissions blocked sunlight to the turf, which would have resulted in stomatal closure and prevented gas exchange from the turf during the measurement period.
Mulch showed the highest N2O flux among all landscapes over all four measurement dates (Figure 4). Tis finding O flux measured in mulched plots. In addition,
suggests that hardwood mulch may produce intermittent anaerobic soil conditions that intensifies N losses through denitrification. Further, irrigation appeared to contribute to elevated N2
except Mulch, N2O flux primarily occurred following irrigation and decreased over time, with no detected amounts two weeks after irrigation/fertilization for any landscapes. Interestingly, there was no N2O flux occurring from the Sand-
Capped Lawn Treatment. Gas emission measurements will be repeated during the summer of 2022.
Subsurface temperatures were monitored from January to August 2021 at the 2 in. (5.08 cm.) soil depth. Data were collected as daily high, low, and average temperatures for all landscapes. As seen in Figure 5., xeriscaping and artificial turf are more sensitive to ambient temperature changes than the other landscapes. For example, during an unusually cold period in February 2021, the lowest temperatures were observed on Xeriscape and Artificial turf (AT). However, during the warmer times of the year, their temperatures became greatly higher than that of the Sand-Capped lawn and St. Augustinegrass lawn, especially when with respect to daily high and daily average temperatures. Te daily high temperature for the two lawn types never exceeded 30 degrees C (86 degrees F) during the summer, and in comparison, the daily high temperature of Xeriscape and AT were regularly within the 30 to 45 degree C (86 to 113 degrees F) temperature range. Te high subsurface temperature of Xeriscape and AT could have an influence on surface thermal comfort and also may alter the soil microbial activities, which are worth a further investigation in the future study. More extensive measurements including radiation measurements will also be taken during summer 2022.
Figure 4. N2
O flux of each landscape type, measured prior to (7/28/21) and at one-day, seven-days, and 14-
days after the 8/2/21 fertilization and irrigation event. Measurement was conducted in the morning on each day. Error bars represent standard error.
Figure 5. Daily high subsurface (2 in. [5.08 cm.] soil depth) temperature of all landscapes in the Texas A&M Landscape Study.
TPI Turf News September/October 2022
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