Chamomile plant material effects on soil nitrogen dynamics and ammonia-oxidizers to mitigate greenhouse gas emissions from maize fields

Abstract

Commonly, agricultural practices utilize urea as a nitrogen (N) source, which can lead to N losses to the environment. Application of urease inhibitors (UIs) or nitrification inhibitors (NIs) can mitigate these losses to some extent but not completely. A preliminary study showed that 2-Cyclopenten-1-one (CCO), an organic compound derived from chamomile (Chamomila recutita L.) can inhibit soil urease activity and also nitrification and therefore has the potential to act as a dual-function inhibitor for decreasing fertilizer-induced N losses and increasing N use efficiency. In this study, a field experiment was conducted to evaluate the effect of CCO on N transformations and NH3, N2O and CH4 emissions from soil, and monitor changes in the ammonia oxidizer amoA gene abundance. Three replicates of five fertilized treatments were included: Urea (fertilizer only), thiophosphoric triamide (NBPT) (a urease inhibitor), dicyandiamide (DCD) (a widely used synthetic nitrification inhibitor), NBPT combined with DCD, and CCO, along with an unfertilized control.The results indicated that, the ability of CCO to reduce N losses and improve maize yield was potentially superior to DCD, NBPT, or the combination of DCD and NBPT. Compared with the urea treatment, the addition of CCO significantly reduced urease activity and nitrification, which subsequently increased the content of NH4+-N and decreased the content of NO3--N in the soil during the maize growth period. Moreover, the cumulative NH3 and N2O emissions, global warming potential (GWP) and greenhouse gas intensity (GHGI) of the maize field were lowest from the CCO applied plots during the growth season, decreasing by 32.5 %, 21.94 %, 7.69 % and 20.92 %, respectively, compared to urea treatment. Notably, CCO application significantly reduced the abundance of ammonia-oxidizing archaea and bacteria in soil. These results suggest that CCO is effective for suppressing urease activity and the nitrification rate in soil and has the potential to be a novel naturally sourced dual-purpose inhibitor.