Dynamics of CO2 efflux from the substrate root system of container-grown plants associated with irrigation cycles

Abstract

In intensive horticultural crops, the choice of growing media and the adequate management of irrigation must ensure an optimal trade-off between aeration and water supply to roots. The proportion of gas-filled pores and their composition can be strongly affected by the water status and hence by irrigation. In this context, continuous measurement of gas exchange and water status of the growing medium could bring out some insights into how irrigation events affect root activity and aeration in a time scale of minutes to several hours. For this purpose, a measuring system was developed that measured the CO 2 efflux rate from the entire substrate root system of pot plants while their shoots were kept outside, undisturbed. It was able to monitor four plants at a time for several weeks at a rate of one measurement per plant every 10 min, thus tracing the dynamics of CO 2 efflux through a great many irrigation cycles. The results showed a marked pattern of CO 2 efflux around each irrigation event, consisting mainly of a sharp, conspicuous peak followed by a depression until a threshold in substrate water potential was reached. Analysis of these data suggests that the pattern is imposed mainly by the effects of irrigation and water content on the mobility of gases in the growing medium. The peak can be explained by the CO 2 -enriched air being displaced by the water added to the growing medium in the pot, and the following depression can be the result of the reduced mobility of gases when substrate water content is high. In spite of the great variation in the instantaneous efflux rate of CO 2 , the integration of these CO 2 values for the entire day provides a rather predictable value given the root biomass and does not seem to be affected by the number of irrigation events that occur in a given day.

Organic Fertilization of Growing Media: Response of N Mineralization to Temperature and Moisture

“…Destructive samples were used to measure NH 4 + -N and NO 3 − -N contents after 3, 7, 14, 28, and 49 days. They consisted of 90 mL vials filled with growing media depending on its bulk density (Table 1), i.e., 16,18,11, and 17 g dw per vial for GM1, GM2, GM3, and GM4, respectively. Vials were destroyed at each date for measurements.…”

“…The microbe-mediated N mineralization rate and the microbial community composition are highly variable and dependent on several factors such as growing media temperature, air porosity, and moisture content, as well as on the nature of the organic fertilizer source and the growing media composition (particle size and composition) [17][18][19]. The C:N ratio of growing media can also impact organic fertilizer mineralization.…”

Comparison of Fertilizer Nitrogen Availability, Nitrogen Immobilization, Substrate Carbon Dioxide Efflux, and Nutrient Leaching in Peat-lite, Pine Bark, and Pine Tree Substrates

“…Because root respiration is also a source of CO 2 in the soil/substrate, it is important to take into account that the CO 2 measured is not solely a result of microbial respiration. Soil CO 2 efflux is influenced by a number of factors, including soil/substrate quality and organic matter content, temperature, soil moisture, root biomass, nutrient availability, and microbial activity and biomass (Casadesus et al, 2007;Fog, 1988;Wang et al, 2003).…”

Changes in Chemical and Physical Properties of Pine Tree Substrate and Pine Bark During Long-term Nursery Crop Production

“…Because root respiration is also a source of CO 2 in the soil, it is important to also consider it as a source of CO 2 evolution from a soil/substrate in addition to microbial respiration. Soil respiration/ efflux (by plant roots or microbes) is influenced by a number of factors, including soil/ substrate quality and organic matter content, temperature, soil moisture, root biomass, and microbial activity and biomass (Casadesus et al, 2007;Ding et al, 2007;Fog, 1988;Steinweg et al, 2008;Wang et al, 2003).…”