Abstract
Nitrification inhibitors (NIs) have been used extensively to reduce nitrogen losses and increase crop nitrogen nutrition. However, information is still scant regarding the influence of NIs on nitrogen transformation, nitrous oxide (N2O) emission and nitrogen utilization in plastic-film-mulched calcareous soil under high frequency drip-fertigated condition. Therefore, a field trial was conducted to evaluate the effect of nitrapyrin (2-chloro-6-(trichloromethyl)-pyridine) on soil mineral nitrogen (N) transformation, N2O emission and nitrogen use efficiency (NUE) in a drip-fertigated cotton-growing calcareous field. Three treatments were established: control (no N fertilizer), urea (225 kg N ha-1) and urea+nitrapyrin (225 kg N ha-1+2.25 kg nitrapyrin ha-1). Compared with urea alone, urea plus nitrapyrin decreased the average N2O emission fluxes by 6.6–21.8% in June, July and August significantly in a drip-fertigation cycle. Urea application increased the seasonal cumulative N2O emission by 2.4 kg N ha-1 compared with control, and nitrapyrin addition significantly mitigated the seasonal N2O emission by 14.3% compared with urea only. During the main growing season, the average soil ammonium nitrogen (NH4+-N) concentration was 28.0% greater and soil nitrate nitrogen (NO3--N) concentration was 13.8% less in the urea+nitrapyrin treatment than in the urea treatment. Soil NO3--N and water-filled pore space (WFPS) were more closely correlated than soil NH4+-N with soil N2O fluxes under drip-fertigated condition (P<0.001). Compared with urea alone, urea plus nitrapyrin reduced the seasonal N2O emission factor (EF) by 32.4% while increasing nitrogen use efficiency by 10.7%. The results demonstrated that nitrapyrin addition significantly inhibited soil nitrification and maintained more NH4+-N in soil, mitigated N2O losses and improved nitrogen use efficiency in plastic-film-mulched calcareous soil under high frequency drip-fertigated condition.
Highlights
As a kind of potential greenhouse gas (GHG), nitrous oxide (N2O) causes climate change and indirectly contributes to stratospheric ozone depletion [1], and its global warming potential (GWP) is about 298 times that of carbon dioxide (CO2) over a 100 yrs time horizon [2]
Several previous studies suggest that nitrification accounts for most N2O emission in well-aerated soil below 60% water-filled pore space (WFPS), whereas denitrification reaction accounts for most N2O emission when soil moisture exceeds 70% WFPS [4,5]
We previously showed that nitrapyrin was more effective than dicyandiamide (DCD) in controlling nitrification process, and nearly as effective as 3, 4-dimethylpyrazole phosphate (DMPP) in calcareous soil with sandy, loam and clay texture [17]
Summary
As a kind of potential greenhouse gas (GHG), nitrous oxide (N2O) causes climate change and indirectly contributes to stratospheric ozone depletion [1], and its global warming potential (GWP) is about 298 times that of carbon dioxide (CO2) over a 100 yrs time horizon [2]. In China, agricultural intensification and heavy fertilizer use have led to an increase in N2O emission losses, the contribution of croplands to the national total of fertilizer N-induced N2O (FIE-N2O) increased from 79% to 92% only in the period of 1980–2000 [3]. Agricultural N2O emission has long been studied, whether N2O is mainly derived from nitrification process under aerobic conditions, or from denitrification process under either anaerobic or aerobic conditions is still inconclusive. Several previous studies suggest that nitrification accounts for most N2O emission in well-aerated soil below 60% water-filled pore space (WFPS), whereas denitrification reaction accounts for most N2O emission when soil moisture exceeds 70% WFPS [4,5]. Recent studies show that denitrification prevails over nitrification during N2O production for irrigated dryland soils or more humid soils initially [6,7]
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