Contribution of the Maize Root Respiration to Total Soil CO2 Emission

Soil carbon dioxide (CO2) measurements usually cover total CO2 emission but do not specifically consider root respiration. Therefore, in this study an experiment was conducted to measure root respiration, in which maize was cultivated and monitored from planting to grain filling stage to assess its root contributions to total CO2 emission. During this period, CO2 emissions were measured from the planted (PL) and plant-free (PF) soil surfaces. The difference between the applications PL and PF were considered to be maize root CO2 emission as root exclusion (RE) method. In another method, the maize root was removed from the soil immediately after it was placed into the chamber to evaluate its respiration called excised root method. Five measurements were conducted throughout the maize maturation period using measurements of CO2 emissions, soil temperature, soil moisture, and root weights. According to RE method significant relationship between PL and PF was observed and revealed that root CO2 emissions accounted for 34.3% of total soil emissions. Also, a strong positive correlation was found between root biomass and CO2 emissions. Specific CO2 emission declined by following plant growth. Root CO2 emissions in excised roots were higher than RE method; in some measurements, root emissions even exceeded the total CO2. The higher root respiration in relation to total emissions is likely related to the increased exposure of the roots to air following their extraction from the soil. In conclusion, around one fourth of the CO2 emission of soil is attributed to roots, and the difference method is considered more reliable for determining root CO2 emissions in plants.