Control of NO3 − and N2O emissions in agroecosystems: A review

Abstract

Energized electron flows through biological systems sustain nature's complexity. They drive bacterial, archaeal, and fungal oxidation-reduction processes and enable to introduce CO 2 and N 2 from the atmospheric pool. Electron flux-based food webs convert soil organic matter (SOM) in virgin forest and permafrost soils, over-fertilized agricultural land, grassland systems, compost/wastewater treatment plants, oceans, rain forests, savannahs, and forests of the temperate climate zones, and have their strategy adapted on the system in which they are active. Thus, the electron driving power is responsible in our industrializing world that carbon and nitrogen returns to the atmosphere presently with an annual N 2 O-N proportion of 0.5 to 4.2 terragrams (Tg) or an annual atmospheric N 2 O-N increase of 0.25 %. N 2 O is a 300-times more potent greenhouse gas than CO 2 . Nature's water-soluble soil carbon (C H2O )/NO 3 − ratio balancing is seen as a model of how N 2 O emissions could be kept in a tolerable range. Sub strategies beyond are (a) an annual 400-800 terragrams (Tg) photosynthate-C (90-95 % sugars) release into plant rhizospheres, (b) spot-wise N enriching animal excrement and wide C/N ratio litter fall distributions, (c) viral shunts or life shortcuts to supporting O 2 consuming, N supplying, and denitrifying recycler communities, (d) subterranean organic-inorganic soil components mixing and O 2 diffusion promoting NO 3 − formation, and (e) the release of nitrification inhibiting compounds as neem, karanjin, or specific humic acids which help in controlling nitrate formation and denitrification. Soil microbial transport vehicles are fungal hyphae, plant roots, and subterranean animals. Through their activities, aerobic-anaerobic gradients in the soil crumb mosaics emerge. Plant root intertissue spaces, animal guts, and co-transported soil crumbs where under carbon-dominated C H2O /NO 3 − ratios preferred microbes reside are mobile locations in well-aerated soils. In such reduction-equivalent surplus environments, denitrifying communities are forced to use during anaerobic respiration available nitrate-, nitrite ions, NO, and N 2 O economically. Though at carbon-dominated C H2O /NO 3 − ratios more N 2 O is reduced to N 2 than in nitrate surplus environments, a complete prevention of N 2 O emissions is not a reality and even not desirable from the climate point of view. After describing N 2 O formation and emissions from a compost pile, a municipal wastewater treatment plant, a constructed wetland, and mineral N-fertilizer, sewage sludge or nitrification inhibitor-stabilized N-fertilizer amended soils with their aerobic-anaerobic mosaics, this review tries to deduce exercisable CN (C H2O /NO 3 ) ratio shaping and N 2 O emission lowering strategies for ecologists, agriculturists, and waste managers in our industrializing world.

Differential Regulation of Stomatal Conductance as a Strategy to Cope With Ammonium Fertilizer Under Ambient Versus Elevated CO2

“…Both nitrate and ammonium are the major N forms available in soils for plants (Andrews et al., 2013; Tegeder and Masclaux-Daubresse, 2017). In both natural and agricultural soils, microbial processes in soils favor a mixed nutrition with fluctuating contents of the respective sources depending on the environmental conditions of temperature and soil water content and the type of fertilizers applied, among other factors (Benckiser et al., 2015). In addition, when both inorganic-N sources are available in plants, ammonium is preferentially taken up and assimilated into organic molecules due to its more chemically reduced status than nitrate, thus saving metabolic energy during its assimilation (Andrews et al., 2013).…”

Effects of boric acid on urea‐N transformation and 3,4‐dimethylpyrazole phosphate efficiency

“…DMPP did not inhibit urea hydrolysis in this study. DMPP only affects ammonia‐oxidizing bacteria (AOB) in soil 30–33 . Several previous studies have found that nitrification inhibitors rarely affect the hydrolysis of urea 16, 34 …”

“…This is probably due to the high nitrification potential in Che amplifying the inhibitory effect. Additionally, DMPP has a stronger inhibitory effect on AOB than AOA 13, 30, 31, 33 . Boric acid addition (UB) exhibited a significant inhibition effect on nitrification at an early stage of incubation and the inhibition efficiency decreased following incubation progress in both soils.…”

Nitrogen Related Diffuse Pollution from Horticulture Production—Mitigation Practices and Assessment Strategies

“…Some of the highest fluxes to date have been measured in irrigated and fertilized systems [48,49]. N 2 O emissions from cultivated soils result from the biological nitrification and denitrification processes [50]. Thus, the understanding of the soil and environmental factors regulating the microbial populations is necessary to choose appropriate N 2 O mitigation strategies.…”