Bulk and spatially resolved extracellular metabolomics of free-living nitrogen fixation

Soil microorganisms drive ecosystem function, but challenges of scale between microbe and ecosystem hinder our ability to accurately quantify and predictively model the soil microbe-ecosystem function relationship. Quantifying this relationship necessitates studies that systematically characterize multi-omics of soil microorganisms and their activity across sampling scales from spatially resolved to bulk measures, and structural complexity, from liquid pure culture to in situ. To address this need, we cultured two diazotrophic bacteria in liquid and solid media, with and without nitrogen (N) to quantify differences in extracellular metabolites associated with nitrogen fixation under increasing environmental structural complexity. We also quantified extracellular metabolites across sampling scales including bulk sampling via GC-MS analysis and spatially resolved analysis via MALDI mass spectrometry imaging. We found extracellular production of inorganic and organic N during free-living nitrogen fixation activity, highlighting a key mechanism of terrestrial N contributions from this process. Additionally, our results emphasize the need to consider the structural complexity of the environment and spatial scale when quantifying microbial activity. We found differences in metabolite profiles between culture conditions, supporting previous work indicating environmental structure influences microbial function, and across scales, underscoring the need to quantify microbial scale conditions to accurately interpret microbial function.

Optimization of Nitrogen Demand in Vegetables by Different Impacts on Autotrophic and Heterotrophic Nitrification

Aims The understanding of the interactions between N transformations and N uptake by plants in greenhouse soils with large N accumulation is still not clear. The aim is to understand the plant- soil interactions (vegetables) on N transformations with respect to N supply. Methods 15N tracing studies were conducted in two greenhouse soils to simultaneously quantify soil gross N transformation and plant N uptake rates using the Ntraceplant tool. Results There were significant feedbacks between vegetable N uptake and soil gross N transformation rates, whether soil N accumulation occurred or not. Plant NO3– uptake rates (UNO3) were higher than the NH4+ uptake rates (UNH4), which is consistent with the NO3–-preference of the vegetable plants studied. While UNH4 was still responsible for 6-49% of total N uptake rates, significantly negative relationships between UNH4 and NH4+ immobilization rate and autotrophic nitrification rate (ONH4) were observed. ONH4 was significantly inhibited in the presence of plants and decreased with time. ONH4 (1.11 mg N kg-1 d-1) was much lower than UNO3 (8.29 mg N kg-1 d-1) in the presence of plants. However, heterotrophic nitrification rate (ONrec), which ranged from 0.10 to 8.11 mg N kg-1 d-1 was significantly stimulated and was responsible for 5-97% of NO3– production in all plant treatments, providing additional NO3– to meet N requirements of plants and microorganisms.Conclusions The management of organic N fertilizers should be improved to stimulate inorganic N production via heterotrophic nitrification in greenhouse cultivation.

N2O Emissions from Two Austrian Agricultural Catchments Simulated with an N2O Submodule Developed for the SWAT Model

Nitrous oxide (N2O) is a potent greenhouse gas stemming mainly from nitrogen (N)-fertilizer application. It is challenging to quantify N2O emissions from agroecosystems because of the dearth of measured data and high spatial variability of the emissions. The eco-hydrological model SWAT (Soil and Water Assessment Tool) simulates hydrological processes and N fluxes in a catchment. However, the routine for simulating N2O emissions is still missing in the SWAT model. A submodule was developed based on the outputs of the SWAT model to partition N2O from the simulated nitrification by applying a coefficient (K2) and also to isolate N2O from the simulated denitrification (N2O + N2) with a modified semi-empirical equation. The submodule was applied to quantify N2O emissions and N2O emission factors from selected crops in two agricultural catchments by using NH4NO3 fertilizer and the combination of organic N and NO3− fertilizer as N input data. The setup with the combination of organic N and NO3− fertilizer simulated lower N2O emissions than the setup with NH4NO3 fertilizer. When the water balance was simulated well (absolute percentage error <11%), the impact of N fertilizer application on the simulated N2O emissions was captured. More research to test the submodule with measured data is needed.

Use of Digestate as Organic Amendment and Source of Nitrogen to Vegetable Crops

Anaerobic digestion is a valuable process to use livestock effluents to produce green energy and a by-product called digestate with fertilising value. This work aimed at evaluating the fertilising value of the solid fraction (SF) of a digestate as an organic amendment and as a source of nitrogen to crops replacing mineral N. A field experiment was done with two consecutive vegetable crops. The treatments were: a control without fertilisation; Ni85 mineral fertilisation with 85 kg ha−1 of mineral N; fertiliser with digestate at an increasing nitrogen application rate (kg N ha−1): DG-N85 DG-N170, DG-N170+85, DG-N170+170; fertilisation with digestate together with Ni: DG-N85+Ni60, DG-N170+Ni60, DG-N170+Ni25. The results showed a soil organic amendment effect of the SF with a beneficial effect on SOM, soil pH and exchangeable bases. The SF was able to replace part of the mineral N fertilisation. The low mineralisation of the stable organic matter together with some immobilisation of mineral N from SF caused low N availability. The fertilisation planning should consider the SF ratio between the organic N (NO) and total N (TKN). Low NO:TKN ratios (≈0.65) needed lower Ni addition to maintaining the biomass production similar to the mineral fertilisation.

Influence of Long Term Fertilization and Manures on Soil Physical and Chemical Properties of Udorthentic Chromusterts

To study the effect of different nutrient management practices on different soil physical and chemical properties in the permanent manurial experiment field of Tamil Nadu Agricultural University, which was established during 1982 at Agriculture Research Station, Kovilpatti. Soil physical and chemical properties are mainly affected by the continuous application of fertilizers or manures from years together. To study the above mentioned properties of soil the soil samples were collected from the permanent manurial experiment of kovilpatti where the Randomized Block Design (RBD) was followed with nine different treatments viz., T1- Control; T2- 100 % RDF (40:20:40 NPK kg ha-1); T3- 50% RDF (20:10:20 NPK kg ha-1); T4- 50% N (Crop residues); T5- 50 % N (FYM); T6- 50 % Inorganic N+ 50% organic N (crop residues) + P (50%) + K (50%) ; T7- 50 % Inorganic N+ 50% organic N (FYM) + P (50%) + K (50%); T8- 100 % RDF + 25 kg ZnSO4 ha-1; T9- FYM - 12.5 t ha-1. The effect of these treatments along with the depth (0-15 cm; 15-30 cm and 30-45 cm) was compared. The treatment receiving organics viz., T9- FYM - 12.5 t ha-1 was observed to be the best in all the physical and chemical properties which was then followed by INM viz., T7- 50 % Inorganic N+ 50% organic N (FYM) + P (50%) + K (50%) and T6- 50 % Inorganic N+ 50% organic N (crop residues) + P (50%) + K (50%).

A review of the importance of mineral nitrogen cycling in the plant-soil-microbe system of permafrost-affected soils – changing the paradigm

The paradigm that permafrost-affected soils show restricted mineral nitrogen (N) cycling in favor of organic N compounds is based on the observation that net N mineralization rates in these cold climates are negligible. However, we find here that this perception is wrong. By synthesizing published data on N cycling in the plant-soil-microbe system of permafrost ecosystems we show that gross ammonification and nitrification rates in active layers were of similar magnitude and showed a similar dependence on soil organic carbon (SOC) and total nitrogen (TN) concentrations as observed in temperate and tropical systems. Moreover, high protein depolymerization rates and only marginal effects of C:N stoichiometry on gross N turnover provided little evidence for N limitation. Instead, the rather short period when soils are not frozen is the single main factor limiting N turnover. High gross rates of mineral N cycling are thus facilitated by released protection of organic matter in active layers with nitrification gaining particular importance in N-rich soils, such as organic soils without vegetation. Our finding that permafrost-affected soils show vigorous N cycling activity is confirmed by the rich functional microbial community which can be found both in active and permafrost layers. The high rates of N cycling and soil N availability are supported by biological N fixation, while atmospheric N deposition in the Arctic still is marginal except for fire-affected areas. In line with high soil mineral N production, recent plant physiological research indicates a higher importance of mineral plant N nutrition than previously thought. Our synthesis shows that mineral N production and turnover rates in active layers of permafrost-affected soils do not generally differ from those observed in temperate or tropical soils. We therefore suggest to adjust the permafrost N cycle paradigm, assigning a generally important role to mineral N cycling. This new paradigm suggests larger permafrost N climate feedbacks than assumed previously.

The Combined Effect of Nitrogen Treatment and Weather Conditions on Wheat Protein-Starch Interaction and Dough Quality

The objective of this field crop study was to compare the effect of organic (cattle manure, off-season cover crop) and mineral N (NH4NO3; 0, 50, 100° 150 kg N ha−1) fertilizers on (i) gluten-starch interaction, and (ii) rheological properties of winter wheat dough. Data were collected from the long-term field experiment located in the Baltic Sea region (58°22’ N, 26°40’ E) in years 2013–2017. The amount of minuppueral N 150 kg ha–1 applied in two parts before flowering ensured higher gluten content (31 ± 3.3%) and dough quality (81 ± 7.4 mm) due to more positive interactions between gluten proteins and starch granules. The quality of dough was more variable in organic treatments (ranged up to 33%) because the availability of organic N was more variable and sensitivity to the weather conditions was higher. The mean variability of different dough properties over trial years under organic treatments was 1.4–2.0 times higher than in the treatment with 150 kg N ha−1.

Substitution of Chemical Fertilizer with Organic Fertilizer Affects Soil Total Nitrogen and Its Fractions in Northern China

The impact of chemical to organic fertilizer substitution on soil labile organic and stabilized N pools under intensive farming systems is unclear. Therefore, we analyzed the distribution of soil total N (STN), particulate organic N (PON), microbial biomass N (MBN), dissolved organic N (DON), and mineral N (NO3− and NH4+) levels down to 100 cm profile under wheat–maize rotation system in northern China. The experiment was established with four 270 kg ha−1 N equivalent fertilizer treatments: Organic manure (OM); Organic manure with nitrogen fertilizer (OM + NF); Nitrogen fertilizer (NF); and Control (CK). Results found that the OM and OM + NF treatments had significantly higher STN, PON, MBN, DON, and NO3− contents in 0–20 cm topsoil depths. Conversely, the NF treatment resulted in the highest (p < 0.01) DON and NO3− depositions in 40–100 cm subsoil depths. The NH4+ contents in selected profile depths were significantly highest (p < 0.01) under OM treatment. The correlations between STN and its fractions were positively significant at 0–10 and 10–20 cm topsoil depths. Our results suggest that partial substitution of chemical fertilizer with organic manure could be a sustainable option for soil N management of intensive farming systems.

Pengaruh Pupuk Kandang Plus terhadap Pertumbuhan dan Produksi Jagung Manis (Zea mays saccharata) di Kabupaten Grobogan

<p>Manure plus is manure’s nutrition improvement by the addition of organic N (<em>Leucaena leucocephala</em>) and nature P (rock phosphate). The aim of this research are to evaluate the effect of ‘manure plus’ on growth and production of sweet corn. This research was conducted experimentally using monofactor Randomized Block Design with seven treatments and four replications. The treatments are P0 (ZA + TSP), P1 (Cattle manure + ZA + TSP), P2 (Goat manure + ZA + TSP), P3 (Poultry manure + ZA + TSP), P4 (Cattle manure + RP + + <em>Leucaena</em><em> l</em><em>eucocephala</em>), P5 (Goat manure + RP+ <em>Leucaena </em><em>l</em><em>eucocephala</em>), P6 (Poultry manure + RP + <em>Leucaena </em><em>l</em><em>eucocephala</em>). All plots were given KCl (150 kg K₂O/ha). The parameters were plant height, leaf’s number, cob length, cob diameter, sum of seed row, and production of sweet corn. Data were subjected to analysis of variance and followed DMRT at α = 5%. The result showed that cob diameter and sum of seed row of P4 had no significantly different compared to P1, P5 had no significantly different compared to P2, P6 had no significantly different compared to P3. The leaf’s number of P4 had no significantly different compared to P1, P5 had no significantly different compared to P2, whereas P3 had leaf’s number more than P6. All treatment had no significant effect towards plant height, cob length and production of sweet corn. Based on the research, manure plus can be used to substitute the role of manure + ZA + TSP.</p>