Nitrification under the influence of long-term fertilizer application in a tropical vertisol (original) (raw)
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Soil Biology and Biochemistry, 2016
In the majority of agricultural soils, ammonium (NH +) is rapidly converted to nitrate (NO 3-) in the biological ammonia and nitrite oxidation processes known as nitrification. The often rate-limiting step of ammonia oxidation to nitrite is mediated by ammonia oxidizing bacteria (AOB) and ammonia oxidizing archaea (AOA). The response of AOA and AOB communities to organic and conventional nitrogen (N) fertilizers, and their relative contributions to the nitrification process were examined for an agricultural silage corn system using a randomized block design with 4 N treatments: control (no additional N), ammonium sulfate (AS) fertilizer at 100 and 200 kg N ha-1 , and steer-waste compost (200 kg total N ha-1) over four seasons. DNA was extracted from the soil, and real-time PCR and 454-pyrosequencing were used to evaluate the quantity and diversity of the amoA gene which encodes subunit A of ammonia monooxygenase. Soil pH, nitrate pools, and nitrification potentials were influenced by ammonium and organic fertilizers after the first fertilization, while changes in AOB abundance and community structure were not apparent until after the second fertilization or later. The abundance of AOA was always greater than AOB but was unaffected by N treatments. In contrast, AOB abundance and community structure were changed significantly by ammonium fertilizers. Specific inhibitors of nitrification were used to evaluate the relative contribution of AOA and AOB to nitrification. We found that AOB dominantly contributed to potential nitrification activity determined at 1 mM ammonium in soil slurries and nitrification potential activity was higher in soils treated with ammonium fertilizers relative to control soils. However, AOA dominated gross nitrification activity in moist soils. Our result suggests that AOB activity and community are more responsive to ammonium fertilizers than AOA but that in situ nitrification rate is controlled by ammonium availability in this agricultural soil. Understanding this response of AOA and AOB to N fertilizers may contribute to improving strategies for the management of nitrate production in agricultural soils.
The Scientific World JOURNAL, 2001
Mineralization of soil organic matter is governed by predictable factors with nitrate-N as the end product. Crop production interrupts the natural balance, accelerates mineralization of N, and elevates levels of nitrate-N in soil. Six factors determine nitrate-N levels in soils: soil clay content, bulk density, organic matter content, pH, temperature, and rainfall. Maximal rates of N mineralization require an optimal level of air-filled pore space. Optimal air-filled pore space depends on soil clay content, soil organic matter content, soil bulk density, and rainfall. Pore space is partitioned into water- and air-filled space. A maximal rate of nitrate formation occurs at a pH of 6.7 and rather modest mineralization rates occur at pH 5.0 and 8.0. Predictions of the soil nitrate-N concentrations with a relative precision of 1 to 4 μg N g–1of soil were obtained with a computerized N fertilizer decision aid. Grain yields obtained using the N fertilizer decision aid were not measurably ...
Short-term competition between crop plants and soil microbes for inorganic N fertilizer
Soil Biology and Biochemistry, 2010
Bacteria Fungi Gross N transformations Inorganic N fertilizer qPCR 15 N tracer a b s t r a c t Agricultural systems that receive high amounts of inorganic nitrogen (N) fertilizer in the form of either ammonium (NH 4 þ ), nitrate (NO 3 À ) or a combination thereof are expected to differ in soil N transformation rates and fates of NH 4 þ and NO 3 À . Using 15 N tracer techniques this study examines how crop plants and soil microbes vary in their ability to take up and compete for fertilizer N on a short time scale (hours to days). Single plants of barley (Hordeum vulgare L. cv. Morex) were grown on two agricultural soils in microcosms which received either NH 4 þ , NO 3 À or NH 4 NO 3 . Within each fertilizer treatment traces of 15 NH 4 þ and 15 NO 3 À
Applied Soil Ecology, 2019
Long term fertilizer experiment continues to act as the hotspot for studying the role of microbial interaction in nutrient supplying capacity. Despite plenty of studies, we have limited perception about the response of soil microorganisms to the long term application of fertilizer and manure. Hence, the present study was undertaken with the following treatments: no fertilizer and manure application i.e. control, 100% N (imbalanced fertilizer application), 100% NP (imbalanced fertilizer application), 100% NPK (balanced fertilizer application), 100% NPK + farmyard manure (FYM) at 5 t ha −1 (Integrated nutrient management; INM). The INM treatment had a significant build-up of total organic carbon (TOC), total N (TN) as compared to imbalanced fertilizer application and control. Similarly, INM also had significantly higher N mineralization potential and nitrification potential as compared to control and 100% N treatment. Heterotrophic nitrification rather autotrophic nitrification caused significant difference among different treatments. Microbial biomass and extracellular N cycling enzymes were also promoted substantially in INM. Discriminant function analysis with phospho lipid fatty acid (PLFA) biomarkers had produced arbuscular mycorrhizal fungi (AMF) and eukaryote as an important discriminant biomarker that cumulatively contributed 99.3% of total variations among the treatments and could have differentiated the control, imbalanced fertilizer application from balanced fertilizer application, and INM. Multiple regression showed that the TOC and protease activity are the key regulator of nitrogen (N) mineralization process and path analysis revealed that the NH 4 +-N followed by TOC, Microbial biomass is the important controller of Geometric mean of enzyme activities (GMea).
Soil Biology & Biochemistry, 2000
We conducted a 112-day laboratory incubation of an agricultural soil treated with dairy-waste compost or ammonium sulfate ((NH 4 ) 2 SO 4 ) to examine the role of microbial production and consumption of NO À 3 in controlling soil NO À 3 concentrations. Inorganic N, net N process rates, nitri®cation potentials and gross N process rates were measured at various time periods in the treated soils. Microbial consumption of NO À 3 was not an important process in controlling soil NO À 3 concentrations in these soil systems. Transient growth in the nitri®er population was observed with ammonium sulfate but not compost addition. Nitri®cation rates were signi®cantly correlated with and comprised about 50% of the gross N mineralization rates, suggesting that nitrifying bacteria were not weaker competitors for soil NH 4 than heterotrophs in these systems. 7 (J.M. Norton).
Effects of organic manure on nitrification in arable soils
1991
The production of nitrate by the process of nitrification is highly dependent on other N-transforming processes in the soil. Hence, changes in the type of N compound applied to enrich agricultural soils may affect the production of nitrate. The size and activity of the chemolithotrophic bacterial community were studied in an integrated farming system, with increased inputs of organic manure and reduced inputs of mineral nitrogenous fertilizer, versus conventional farming. The integrated farming had a positive effect on potential nitrifying activity, but not on the numbers of chemolithotrophic nitrifying bacteria as determined by a most probable number technique or by fluorescence antibody microscopy. Cells of the recently described nitrite-oxidizing species Nitrobacter hamburgensis and Nitrobacter vulgaris were just as common as the cells of the well known species Nitrobacter winogradskyi. It was concluded that nitrification is stimulated by integrated farming, presumably by an increased mineralization of ammonium which is not immediately consumed by the crop or immobilized in the heterotrophic microflora of the soil. Since nitrifying bacteria are involved in the production of NO and N20, integrated farming with the application of manure may favour the production of noxious N-oxides.
Nitrification in Agricultural Soils
Agronomy Monograph, 2008
No bacteria have been found that can convert NH 3 to NO 3 − directly (Hooper et al., 1997). Recent evidence suggests that archaea of the phylum Crenarchaeota are also capable of ammonia oxidation, contain genes encoding the key enzymes of this process, and are widespread in soil environments (
Soil Biology & Biochemistry, 2017
Soil ammonia-oxidizing bacteria and archaea (AOB and AOA) convert ammonium/ammonia to nitrite in the process of nitrification. However, the potentially differential responses of these AO to substrate and temperature and the effects of conventional and organic nitrogen management on these responses remains poorly understood. We determined the response of nitrification to ammonium substrate concentration and temperature using an AOB specific inhibitor to distinguish the contribution of AOB and AOA to nitrification. Soils were sampled from cornfield plots that had been treated for four years with contrasting nitrogen sources: control (no additional N), ammonium sulfate at two rates and compost. Nitrification potential and net rates were stimulated for one month after fertilization with ammonium sulfate compared to relatively lower and stable rates in control and compost treated soils. For soils that had been fertilized with ammonium sulfate, the proportion of nitrification mediated by AOB in slurry assays was over 90% at 1.0 mM but less than 50% at 0.01 mM. Kinetic analysis showed maximum nitrification activity (V max) for AOB ranged from 0.32 to 4.8 mmol N kg À1 d À1 with a half saturation constant (K m) of 14e160 mM ammonium; parameters were higher for soils from ammonium sulfate treated plots. V max and K m for AOA averaged 0.24 mmol N kg À1 d À1 and 4.28 mM ammonium with no effect of field treatment. The proportion of nitrification due to AOA was lowest at 5 C, increased with temperature, and was near to 100% at 50 C; optimum temperature was 41 C for AOA versus 31 C for AOB. Understanding the kinetic and temperature response of microbes responsible for nitrification may allow ecosystem models to include these populations as dynamic components driving nitrogen flux.