Biostimulants decreased nitrogen leaching and NH3 volatilization but increased N2O emission from plastic-shed greenhouse vegetable soil

Abstract

Biostimulant application is an effective strategy to enhance soil fertility and plant growth. However, its comprehensive impacts on nitrogen (N) uptake and reactive N (Nr) losses via leaching, ammonia (NH3) volatilization, and nitrous oxide (N2O) emission from plastic-shed greenhouse vegetable system are still little known. Therefore, a field experiment was conducted with cauliflower-tomato growth rotation (from September 6, 2018, to July 17, 2019) receiving three biostimulants, i.e., humic acid (HA), algae extract (AE), and chitosan (CT), as well as a control without stimulant. The cumulative Nr losses over the cauliflower-tomato growth cycle via leaching, NH3 volatilization, and N2O emission were 104–175 kg N ha–1, 2.32–3.85 kg N ha–1, and 0.70–0.85 kg N ha–1, respectively. Biostimulant application significantly (P < 0.05) retarded the total N leaching by 17–44% in tomato season, while suppressed the NH3 volatilization by 18–38% in cauliflower season. Overall, AE showed the best inhibition efficiency on Nr losses by significantly (P < 0.05) decreasing total N leaching and NH3 volatilization by 36–44% and 38–52% in both vegetable seasons, compare to the control. However, all three biostimulants stimulated the N2O emission under both vegetable cycles. Interestingly, all biostimulant-added treatments promote the cauliflower and tomato yield, particularly following the HA and AE amendments, which bring local farmers approximately 4,384–10,035 yuan RMB ha–1 more income. Enhanced yield under biostimulant treatments was due to higher N uptake capacity and enhanced root morphology. In summary, biostimulants have a contrasting influence on three major Nr lost pathways in greenhouse vegetable production. We recommend that AE is the most optimal biostimulant as it increases vegetable yield and decreases total N leaching and NH3 volatilization while not dramatically increase the N2O emission.