Сarbon exchange in the agroecosystems of maize (Zea mays L.) and rapeseed (Brassica napus L.)

Abstract

The aim of this research was to calculate and compare the C budget metabolic changes for maize (Zea mays L.) and rapeseed (Brassica napus L.), identifying soil seasonal respiratory CO2 emissions (Ra+h) and assimilated photosynthetic CO2 emissions during different growth stages. The research was carried out for maize (Zea mays L.) and rapeseed (Brassica napus L.), during the vegetation period (2014 June - September) at the Training Farm of the Aleksandras Stulginskis University, Kaunas district, Lithuania. The mean soil CO2 emissions were 1.971±0.12 μmol m-2s-1 for maize, and 2.199±0.25 μmol m-2s-1 for rapeseed depending on meteorological conditions and soil Corg concentrations (r = 0.9). Assimilated CO2 rate of maize recorded the highest in the beginning of July (17.74 μmol m-2s-1) at flowering stage (BBCH 40-69), and rapeseed in June (14.44 μmol m-2s-1) at stem growth stage (BBCH 30-50), when crops accumulated the highest biomass due to the most intensive LAI grow (rLAI = 0.9). The mean assimilated CO2 gains of maize were 24% higher than that of rapeseed due to crops’ different biological peculiarities. Net primary productivity (The mean C budget in maize agro-ecosystems was 15.54 t ha-1, while it was 10.30 t ha-1 in rapeseed. NPP) of maize was estimated by 31% and 91% higher than that of rapeseed in July and August, respectively. Therefore, mean NPP was 15.54 t ha-1 in maize and 10.30 t ha-1 in rapeseed agroecosystem. The mean NPP of maize was assessed by 66% higher than that of rapeseed during growth period. That indicated higher carbon sequestration potential of maize than that of rapeseed. Consequently, sequestered C gain depends on the crop species and environmental conditions. Moreover, carbon sequestration might be improved due to altering the current flux rates through crop rotation management.