Managing Fertigation Frequency and Level to Mitigate N2O and CO2 Emissions and NH3 Volatilization from Subsurface Drip-Fertigated Field in a Greenhouse

Abstract

Agricultural practices such as water and N management can contribute to greenhouse gas (GHG) emissions. Fertigation frequency and level are the two most important factors of irrigation scheduling. Proper irrigation management can establish moderate moist conditions throughout the crop growth period in the root zone and reduce GHG emissions and NH3 volatilization. The main objective was to evaluate the possibility of reducing soil N2O and CO2 emissions and NH3 volatilization without crop yield reduction by manipulating the subsurface-drip fertigation (SDF) frequency and level. An experiment was carried out adopting three SDF frequencies, High-Frequency (7-day, HF), Medium-Frequency (8-day, MF), and Low-Frequency (10-day fertigation intervals, LF), and two irrigation levels, 80% (I80) and 70% (I70) of amount in farmer’s common practice (1500 m3 ha−1). Urea, N > 46.2% at the rate of 90% of traditional fertilization level (270 Kg N ha−1) was injected with irrigation water. Results indicated that soil N2O, CO2, NO3−-N, NO2−-N, and water-filled pore space increased with fertigation frequency and an opposite pattern for NH4+-N and NH3. HF significantly (p < 0.05) increased crop yield by 45.1% and 49.2% compared to LF, under I80 and I70 levels, respectively. At the same irrigation level, HF was the optimum management practice. Person correlation analysis showed significant correlations between NO2−-N and N2O, CO2 and soil temperature, and NH4+-N and NH3. The study suggests that HF of SDF with emitters buried at 0.15 m depth helps to keep high Chinese cabbage yield increases GHG emissions, but is not significant, and decreases NH3 volatilization.