Side Effects of Nitrification Inhibitors on Non Target Microbial Processes in Soils (original) (raw)
Evaluation of the side effects of nitrification inhibiting agrochemicals in soils
Selected bioassays were used to assess the side effects of agricultural chemicals on microbial activities under laboratory conditions using loamy clay, loam, sandy soil and the nitrification inhibitors (NI) 3,4dimethyl pyrazole phosphate (DMPP), 4-Chlor-methyl pyrazole (ClMP) and dicyandiamide (DCD). The NI influence with concentrations from 1-1000 times the recommended application rate was assessed on the general microbial activity. Also, the dehydrogenase (DHA) and the dimethyl sulfoxide reductase activity (DRA) on the nitrogenase activity (NA) was evaluated. The potential denitrification capacity (PDC), representing nitrogen cycle, specific to soil microbial processes was examined in incubation experiments in the presence of DMPP, ClMP and DCD. DHA was estimated spectrophotometrically and DRA, PDC and NA gas was quantified using gas chromatography. The morphological changes of a nitrifying bacterial consortium in presence of the recommended DMPP field application rate and at 10 times higher concentration were observed under a transmission electron microscopy. The inhibition in the presence of increasing NI concentrations was calculated as no effect level (NOEL), effective dose ED 10 (10% inhibition) and ED 50 (50% inhibition). Dose response curves expressing the inhibition effectiveness was most distinct in sandy soils. Most NI sensitive reacted PDC>DRA>DHA>NA and ClMP added to the three differently structured test soils influenced non-target microbial processes activity at a higher level. Our results clearly showed that the evaluation of agrochemical side effects with soil enzymes exhibited as reliable, sensitive, reproducible and suitable method to investigate soil microbial activity interferences.
2020
ABSTRACTNitrification inhibitors (NIs) applied to soil reduce nitrogen fertilizer losses from agricultural ecosystems. Currently available NIs appear to selectively inhibit ammonia-oxidizing bacteria (AOB), while their impact on other groups of nitrifiers is limited. Ethoxyquin (EQ), a preservative shown to inhibit ammonia-oxidizers (AO) in soil, is rapidly transformed to 2,6-dihydro-2,2,4-trimethyl-6-quinone imine (QI) and 2,4-dimethyl-6-ethoxy-quinoline (EQNL). We compared the inhibitory potential of EQ and its derivatives in vitro with other established NIs that have been applied in an agricultural setting (dicyandiamide (DCD), nitrapyrin (NP), 3,4-dimethylpyrazole phosphate (DMPP)) by evaluating their impact on the activity and growth of five soil-derived strains (two AOB (Nitrosomonas europaea, Nitrosospira multiformis), two ammonia-oxidizing archaea (AOA) (“Candidatus Nitrosocosmicus franklandus”, “Candidatus Nitrosotalea sinensis”), and one nitrite-oxidizing bacterium (NOB) (...
Frontiers in Microbiology, 2020
Nitrification inhibitors (NIs) applied to soil reduce nitrogen fertilizer losses from agro-ecosystems. NIs that are currently registered for use in agriculture appear to selectively inhibit ammonia-oxidizing bacteria (AOB), while their impact on other nitrifiers is limited or unknown. Ethoxyquin (EQ), a fruit preservative shown to inhibit ammonia-oxidizers (AO) in soil, is rapidly transformed to 2,6-dihydro-2,2,4-trimethyl-6-quinone imine (QI), and 2,4-dimethyl-6-ethoxy-quinoline (EQNL). We compared the inhibitory potential of EQ and its derivatives with that of dicyandiamide (DCD), nitrapyrin (NP), and 3,4-dimethylpyrazole-phosphate (DMPP), NIs that have been used in agricultural settings. The effect of each compound on the growth of AOB (Nitrosomonas europaea, Nitrosospira multiformis), ammonia-oxidizing archaea (AOA; "Candidatus Nitrosocosmicus franklandus," "Candidatus Nitrosotalea sinensis"), and a nitrite-oxidizing bacterium (NOB; Nitrobacter sp. NHB1), all being soil isolates, were determined in liquid culture over a range of concentrations by measuring nitrite production or consumption and qPCR of amoA and nxrB genes, respectively. The degradation of NIs in the liquid cultures was also determined. In all cultures, EQ was transformed to the short-lived QI (major derivative) and the persistent EQNL (minor derivative). They all showed significantly higher inhibition activity of AOA compared to AOB and NOB isolates. QI was the most potent AOA inhibitor (EC 50 = 0.3-0.7 µM) compared to EQ (EC 50 = 1-1.4 µM) and EQNL (EC 50 = 26.6-129.5 µM). The formation and concentration of QI in EQ-amended cultures correlated with the inhibition patterns for all isolates suggesting that it was primarily responsible for inhibition after application of EQ. DCD and DMPP showed greater inhibition of AOB compared to AOA or NOB,
FEMS Microbiology Reviews, 2020
ABSTRACTNitrification is the microbial conversion of reduced forms of nitrogen (N) to nitrate (NO3−), and in fertilized soils it can lead to substantial N losses via NO3− leaching or nitrous oxide (N2O) production. To limit such problems, synthetic nitrification inhibitors have been applied but their performance differs between soils. In recent years, there has been an increasing interest in the occurrence of biological nitrification inhibition (BNI), a natural phenomenon according to which certain plants can inhibit nitrification through the release of active compounds in root exudates. Here, we synthesize the current state of research but also unravel knowledge gaps in the field. The nitrification process is discussed considering recent discoveries in genomics, biochemistry and ecology of nitrifiers. Secondly, we focus on the ‘where’ and ‘how’ of BNI. The N transformations and their interconnections as they occur in, and are affected by, the rhizosphere, are also discussed. The NH...
Impact of dimethylpyrazole-based nitrification inhibitors on soil-borne bacteria
Science of The Total Environment, 2021
Soil water content played a key role in the effect of DMPP and DMPSA on soil bacteria. • Both nitrification inhibitors (NIs) shifted non-target bacteria abundances. • The effect of NIs within nitrifiers was highly focused on Nitrosomonas. • DMPSA decreased bacterial-community richness and evenness at high soil moisture. • NIs shifted bacterial interaction networks by decreasing their complexity.
Environmental Practice, 2007
Substantial progress has been made towards land management practices that fulfill the basic requirements of a burgeoning human population. One of them is extensive use of nitrogen-containing chemical fertilizers to boost crop production. Though their use is beneficial, overuse of these fertilizers is causing serious environmental problems associated with emission of NH 3 , N 2 , and N 2 O (the last being an important greenhouse gas implicated both in the greenhouse effect and ozone layer depletion in the stratosphere) to the atmosphere and contamination of ground and surface water resources via nitrate leaching or runoff. Because these losses have both economic and environmental implications, it is high time to utilize a technique that contains nitrogen losses and enhances nitrogen-use efficiency of agricultural crops. To manage nitrogen losses from agricultural fields, different nitrification inhibitors are currently available, and if used along with NH 4-containing fertilizers, they can effectively increase nitrogen-use efficacy and attenuate the emission of greenhouse gases by decelerating the soil nitrification processes resulting from ammonia metabolism.
Biology and Fertility of Soils
Inhibitors of urease and ammonia monooxygenase can limit the rate of conversion of urea to ammonia and ammonia to nitrate, respectively, potentially improving N fertilizer use efficiency and reducing gaseous losses. Winter wheat grown on a sandy soil in the UK was treated with urea fertilizer with the urease inhibitor N-(n-butyl) thiophosphoric triamide (NBPT), the nitrification inhibitor dicyandiamide (DCD) or a combination of both. The effects on soil microbial community diversity, the abundance of genes involved in nitrification and crop yields and net N recovery were compared. The only significant effect on N-cycle genes was a transient reduction in bacterial ammonia monooxygenase abundance following DCD application. However, overall crop yields and net N recovery were significantly lower in the urea treatments compared with an equivalent application of ammonium nitrate fertilizer, and significantly less for urea with DCD than the other urea treatments.
Non-target impacts of the nitrification inhibitor dicyandiamide on soil biota
2010
Intensively grazed dairy pastures in New Zealand routinely receive concentrated inputs of nitrogen (N) both through application of fertiliser and deposition of urine by grazing animals. Leaching of nitrate from soil into aquifers, rivers and lakes is a source of increasing environmental and public health concern. Nitrification inhibitors have been shown to decrease leaching and denitrification from urea- and ammonium-based fertilisers and from urine patches in pastures. To date there have been few studies on effects of nitrification inhibitors on non-target soil biota. Three laboratory experiments were carried out to measure the short term effects of a nitrification inhibitor, dicyandiamide (DCD), on diversity of soil bacterial populations, earthworms and Collembola. Molecular analysis of the soil bacterial community indicated that application of DCD to soil did not affect the composition of the predominant bacterial phyla present in soil, unlike the addition of bovine urine which c...