The influence of the soil matrix on nitrogen mineralisation and nitrification. I. Spatial variation and a hierarchy of soil properties

Soil Research ◽  
1998 ◽  
Vol 36 (3) ◽  
pp. 429 ◽  
Author(s):  
D. T. Strong ◽  
P. W. G. Sale ◽  
K. R. Helyar
Keyword(s):  
Soil Properties ◽  
Water Content ◽  
Organic N ◽  
Small Field ◽  
N Mineralisation ◽  
Mineral N ◽  
Conceptual Tool ◽  
Soil Matrix ◽  
Total N ◽  
Soil Variables

Natural heterogeneity of soil properties was used to explore their influence on nitrogen (N) mineralisation and nitrification in undisturbed small soil volumes (soil cells; c. 1 · 7 cm3 ) sampled from a small field plot (2 m by 3 m). Soil cells (840) were randomly ascribed to 1 of 6 treatments in which soils were retained continuously moist (M10 and M30 treatments) and amended with organic N from clover (Cl10 and Cl30 treatments), dried and rewetted (DW10), or treated with urea (Ur10) (subscripts indicate soil incubation at matric potential - 10 or - 30 kPa). After 20 days of incubation at 24C, each soil cell was analysed for NO-3 -N, NH + 4 -N, pH, bulk density (BD), volumetric water content (θv), water content at - 490 kPa (θv490), and pH buffer capacity (pHBC). On 25 soil cells from each treatment, % clay, % silt, % sand, total N (% N), organic carbon (% C), and 7 cations and anions were also determined. Net N mineralisation and net nitrification occurred in all treatments, and the total mineral N at the end of the incubation was 497, 81, 73, 31, 27, and 31 µg N/g in the Ur10 Cl10, Cl30, M10, M30, and DW10 treatments, respectively. Net N mineralisation in the M30 treatment was 84% of that in the M10 treatment, and net N mineralisation in the Cl30 treatment was 86% of that in the Cl10 treatment. Fluctuations in soil pH varied markedly between treatments and over time, and it was apparent that alkaline processes were occurring in all soil cells. The heterogeneity between soil samples was substantial for all of the soil variables. Soil variables were classified in a hierarchy from the least to the most fundamental based on their stability through time. This ranking provides a conceptual tool for understanding interrelationships between soil properties and for interpreting results of regression analyses. The sampling approach adopted in this study was designed to harness the natural heterogeneity of soil properties in the small field site while keeping other properties and environmental factors, that usually vary over larger distances, constant. Both the extent of heterogeneity of soil properties and the nature of their correlations with NO-3 -N suggested that this technique would be useful in the exploration of how soil properties influence N mineralisation and nitrification.

The influence of the soil matrix on nitrogen mineralisation and nitrification III. Predictive utility of traditional variables and process location within the pore system

Soil Research ◽  
1999 ◽  
Vol 37 (1) ◽  
pp. 137 ◽  
Author(s):  
D. T. Strong ◽  
P. W. G. Sale ◽  
K. R. Helyar
Keyword(s):  
Soil Ph ◽  
Organic N ◽  
Organic Substrates ◽  
Small Field ◽  
N Mineralisation ◽  
Field Plot ◽  
Pore System ◽  
Undisturbed Soil ◽  
Soil Matrix ◽  
Drying And Rewetting

Regression analysis was used to examine the importance of organic nitrogen (%N), soil water content (θv), soil pH, and C: N ratio for predicting N mineralisation in a small field plot. Undisturbed soil cubes (c. 1·7 cm3) were collected from the soil surface and received treatments of drying and rewetting, urea, substrate derived from clover leachate, or no amendment, and were incubated at either –10 or –30 kPa for 20 days. The data confirm the hypothesis that within a small field plot, θv and %N explain most of the variation in net N mineralisation and nitrification. The pore size classes of 0·6–10 and 10–30 µm made disproportionately small and large contributions to N mineralisation, respectively, apparently due to non-uniform distribution of organic N through the pore system. When soluble N substrate was added to the soils, both these pore classes appeared to support mineralisation. We concluded that prior to sampling, the microbial biomass had been more active in the pores 0·6–10 µm, and had nearly exhausted the organic substrates in this pore class, whereas this was not so for the 10–30 µm pore class. Drying and rewetting increased the importance of %N as a predictor of N mineralisation, probably because this treatment disrupted physical protective mechanisms of organic N. Soil pH was generally not a useful predictor of N mineralisation and often seemed to be a dependent rather than an independent variable in relation to nitrification. Neither was C: N ratio a useful predictor of N transformation processes, and this was probably related to physical regulatory mechanisms in the soil.

The influence of the soil matrix on nitrogen mineralisation and nitrification. IV.Texture

Soil Research ◽  
1999 ◽  
Vol 37 (2) ◽  
pp. 329 ◽  
Author(s):  
D. T. Strong ◽  
P. W. G. Sale ◽  
K. R. Helyar
Keyword(s):  
Negative Relationship ◽  
Negative Influence ◽  
Organic N ◽  
N Mineralisation ◽  
Linear Regression Models ◽  
Undisturbed Soil ◽  
Soil Matrix ◽  
Total N ◽  
Material Texture ◽  
Microbial Attack

Small undisturbed soil volumes (c. 1·7 cm3) were collected from the surface of a small field plot. Soil volumes were treated with clover-derived substrate, dried and rewetted, or retained continuously moist from the field. These soil volumes were then incubated for 20 days at a matric water potential of either –10 or –30 kPa. At the end of the incubation the soil was analysed for volumetric water content (θv), NO-3 -N, NH+4 -N, total N (%N), and percentages of sand, silt, and clay. The texture terms were included in linear regression models, together with %N and θv as predictors of N mineralisation and nitrification. Clay and sand were often observed to have a significant influence on N mineralisation and nitrification, but silt rarely appeared to influence these processes. In soils retained continuously moist, %clay had a negative relationship with N mineralisation and nitrification, but this relationship was positive in soils that had been dried and rewetted. The results suggest that during periods of relatively high moisture content, soils that are higher in clay are able to protect organic N more effectively from microbial attack. However, on drying and rewetting, the protective mechanisms of clay are undermined, the relatively large protected reservoirs of organic N in high clay soils become more vulnerable to microbial attack, and these soils therefore experience a greater flush of N mineralisation than soils with lower clay levels. The negative influence of clay in the continuously moist soils was not as clearly observed in the soils incubated at –10 kPa as in soils incubated at –30 kPa, suggesting that the decomposition of organic N resident in larger pores (10–30 µm neck diameter) may not be as strongly regulated by clay as that resident in smaller pores. When soils were treated with clover-derived substrate, clay had a positive relationship with N mineralisation and nitrification rates. This may have been because clay limited the diffusion of partially decomposed organics away from the decomposing microbial population, thereby helping to facilitate more complete decomposition of the organic material. Texture had very little influence on the nitrification of urea-derived ammonium.

scholarly journals Urban soil microbial community and microbial-related carbon storage are severely limited by sealing

2021 ◽  
Vol 21 (3) ◽  
pp. 1455-1465
Author(s):  
Marlon Correa Pereira ◽  
Roisin O’Riordan ◽  
Carly Stevens
Keyword(s):  
Microbial Community ◽  
Soil Properties ◽  
Water Content ◽  
Microbial Activity ◽  
Soil Microbial Community ◽  
C:N Ratio ◽  
N Mineralisation ◽  
Total N ◽  
Soil Microbial ◽  
C Storage

Abstract Purpose Urbanisation causes changes in land use, from natural or rural to urban, leading to the sealing of soil and the replacement of vegetation by buildings, roads and pavements. The sealing process impacts soil properties and services and can lead to negative consequences for microbial attributes and processes in soil. At present, information about the microbial community following soil sealing is limited. As such, we investigated how changes in soil physical and chemical properties caused by sealing affect the soil microbial community and soil ecosystem services. Material and methods Soils were sampled beneath impervious pavements (sealed) and from adjacent pervious greenspace areas (unsealed). Soil properties (total C, total N, C:N ratio and water content) and microbial attributes (microbial biomass C, N-mineralisation and phospholipid fatty acids—PLFA) were measured and correlated. Results and discussion A reduction of total C, total N, and water content were observed in sealed soil, whilst the C:N ratio increased. Sealed soil also presented a reduction in microbial attributes, with low N-mineralisation revealing suppressed microbial activity. PLFA data presented positive correlations with total C, total N and water content, suggesting that the microbial community may be reduced in sealed soil as a response to soil properties. Furthermore, fungal:bacterial and gram-positive:gram-negative bacterial ratios were lower in sealed soil indicating degradation in C sequestration and a consequential effect on C storage. Conclusions Sealing causes notable changes in soil properties leading to subsequent impacts upon the microbial community and the reduction of microbial activity and soil C storage potential.

scholarly journals Effects of two wood-based biochars on the fate of added fertilizer nitrogen—a 15N tracing study

2021 ◽  
Author(s):  
Subin Kalu ◽  
Gboyega Nathaniel Oyekoya ◽  
Per Ambus ◽  
Priit Tammeorg ◽  
Asko Simojoki ◽  
...  
Keyword(s):  
Plant Uptake ◽  
Plant Biomass ◽  
Application Rate ◽  
Control Treatment ◽  
Organic N ◽  
N Leaching ◽  
Soil N ◽  
Mineral N ◽  
Total N ◽  
Application Rates

AbstractA 15N tracing pot experiment was conducted using two types of wood-based biochars: a regular biochar and a Kon-Tiki-produced nutrient-enriched biochar, at two application rates (1% and 5% (w/w)), in addition to a fertilizer only and a control treatment. Ryegrass was sown in pots, all of which except controls received 15N-labelled fertilizer as either 15NH4NO3 or NH415NO3. We quantified the effect of biochar application on soil N2O emissions, as well as the fate of fertilizer-derived ammonium (NH4+) and nitrate (NO3−) in terms of their leaching from the soil, uptake into plant biomass, and recovery in the soil. We found that application of biochars reduced soil mineral N leaching and N2O emissions. Similarly, the higher biochar application rate of 5% significantly increased aboveground ryegrass biomass yield. However, no differences in N2O emissions and ryegrass biomass yields were observed between regular and nutrient-enriched biochar treatments, although mineral N leaching tended to be lower in the nutrient-enriched biochar treatment than in the regular biochar treatment. The 15N analysis revealed that biochar application increased the plant uptake of added nitrate, but reduced the plant uptake of added ammonium compared to the fertilizer only treatment. Thus, the uptake of total N derived from added NH4NO3 fertilizer was not affected by the biochar addition, and cannot explain the increase in plant biomass in biochar treatments. Instead, the increased plant biomass at the higher biochar application rate was attributed to the enhanced uptake of N derived from soil. This suggests that the interactions between biochar and native soil organic N may be important determinants of the availability of soil N to plant growth.

A synoptic approach for crop loss assessment used to study wheat. II. Relationships between soil properties and traditional soil classifications

Soil Research ◽  
1979 ◽  
Vol 17 (2) ◽  
pp. 227 ◽  
Author(s):  
LG Veitch ◽  
BA Stynes
Keyword(s):  
Soil Properties ◽  
Water Content ◽  
Two Dimensions ◽  
Loss Assessment ◽  
Individual Values ◽  
Available Water Content ◽  
Soil Variables ◽  
Crop Loss Assessment ◽  
The Relationship ◽  
Soil Groups

Study of the relationship between soil properties and traditional soil classifications, using the canonical analysis procedure, showed that both a highly significant and a substantial relationship exists. Classification data on average accounts for about 35% of the total variation of the soil variable data, individual values ranging from about 8% for average log salinity to 74% for the -0.1 bar water content of the soil. The analysis showed that classification data in five soil groups could be substantially retained in two dimensions. The soil variables most involved in the first dimension were per cent clay and the -0.1 bar water content of the soil, and in the second dimension, the available water content of the subsoil (30-100 cm), average pH and average log salinity. These results should be useful in other studies where it is desired to incorporate soil information in a model designed to account for variation in one or more measures of interest.

Use of natural heterogeneity in a small field site to explore the influence of the soil matrix on nitrogen mineralisation and nitrification

Soil Research ◽  
1997 ◽  
Vol 35 (3) ◽  
pp. 579 ◽  
Author(s):  
D. T. Strong ◽  
P. W. G. Sale ◽  
K. R. Helyar
Keyword(s):  
Soil Properties ◽  
Multiple Regression ◽  
Multiple Regression Equation ◽  
Regression Equations ◽  
Small Field ◽  
Undisturbed Soil ◽  
Soil Matrix ◽  
Ph Buffering ◽  
Functional Relationships ◽  
Physical Scale

The influence of soil properties on microbiological processes is often examined by comparing the behaviour of taxonomically disparate soils. One of the limitations of this approach is that the results can be confounded by the unmeasured properties which vary between soils of different type or between soils which have had different climatic and management histories. This study tested the hypothesis that the heterogeneity between 100 small contiguous undisturbed soil cubes (about 1·7 cm3), sampled from the surface of a very small field plot (14 by 14 cm), was sufficiently large to use for the exploration of how soil properties influence biological processes. After incubation of the soil for 35 days, the coefficients of variation for nitrate (NO3), ammonium (NH4), gravimetric water content (θg), bulk density (BD), pH buffering capacity (pHBC), and pH were 28, 39, 27, 10, 13, and 2%, respectively. A multiple regression equation predicting nitrate concentration had an r2 value of 0·89 and significantly included 4 predictor variables, with only pH being non-significant. These analyses confirmed the hypothesis. When the values of measured soil properties of adjoining soil cubes were meaned to estimate values for larger soil volumes, the multiple regression equations for predicting NO3 concentration explained more of the variation (r2 values as high as 0·99). However, information concerning the influence of certain soil properties on N mineralisation and nitrification was lost, with only pHBC and BD remaining significant in the regression model. It was concluded that at a given physical scale of investigation, the structure of the spatial variability may determine whether or not a relationship between 2 variables is observed. Smaller samples are more likely to identify functional relationships which may exist between measured variables at the microscale.

The influence of the soil matrix on nitrogen mineralisation and nitrification V. Microporosity and manganese

Soil Research ◽  
1999 ◽  
Vol 37 (2) ◽  
pp. 345 ◽  
Author(s):  
D. T. Strong ◽  
P. W. G. Sale ◽  
K. R. Helyar
Keyword(s):  
Linear Models ◽  
Positive Influence ◽  
Important Variable ◽  
N Mineralisation ◽  
Mineral N ◽  
Soil Matrix ◽  
Drying And Rewetting ◽  
O2 Diffusion ◽  
O2 Supply ◽  
Mn Oxides

Small soil cubes of dimensions 12 by 12 by 12 mm were collected from the surface of a red earth. Treatments were addition of clover substrate or urea, drying and rewetting, or no amendment, after which soils were incubated at either –10 or –30 kPa. Each soil cube was analysed for NO-3 -N, NH+4 -N, total soil N (%N), volumetric water content (θv), microporosity (volume of pores <0·6 µm), and Mn 2+ concentration. Multiple regression analysis was used to determine if microporosity and Mn 2+ contributed uniquely to linear models in which %N and qv were also used to predict N mineralisation and nitrification. In soils incubated at –10 kPa, both microporosity and Mn 2+ had a strong positive influence on N mineralisation and nitrification, whereas in soils incubated at –30 kPa no such influence could be observed. These and other observations suggest that when soils with high microporosity were incubated at –10 kPa, O2 supply to the microbial biomass was limited and the reduction of Mn oxides to divalent Mn was enhanced. Increased substitution of Mn oxides for O2 as terminal electron acceptors in the microbially mediated oxidation of carbon substrates considerably increases H+ consumption. We propose that in the wetter soil (–10 kPa), this process relieves pH stress experienced by N mineralising and nitrifying organisms, thereby increasing their activity, but that in the drier soil (–30 kPa), O2 diffusion is less restricted and this mechanism does not operate appreciably. The influence of microporosity on clover-amended soils was to decrease levels of mineral N and this was attributed to greater denitrification in soils with high microporosity. Neither microporosity nor Mn2+ was an important variable in the prediction of mineral N in the urea-treated soils. This work highlights the interaction of physical, chemical, and biological components of the soil which give rise to microbial microsites and diffusion gradients which are important determinants of soil function.

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

2021 ◽  
Vol 12 (1) ◽  
pp. 248
Author(s):  
Carmo Horta ◽  
João Paulo Carneiro
Keyword(s):  
Organic Amendment ◽  
Application Rate ◽  
Green Energy ◽  
Organic N ◽  
N Availability ◽  
Vegetable Crops ◽  
Mineral N ◽  
Total N ◽  
Ni Addition ◽  
Stable Organic Matter

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.

Nitrogen fluxes in surface soils of 1 - 2-year-old eucalypt plantations in Tasmania

Soil Research ◽  
1998 ◽  
Vol 36 (1) ◽  
pp. 17 ◽  
Author(s):  
X. J. Wang ◽  
P. J. Smethurst ◽  
G. K. Holz
Keyword(s):  
Late Summer ◽  
Soil Core ◽  
N Mineralisation ◽  
Surface Soils ◽  
Mineral N ◽  
Total N ◽  
Available N ◽  
Organic C ◽  
Linear Relationships ◽  
Eucalypt Plantations

To improve our understanding of nitrogen (N) supply in eucalypt plantations in Tasmania, N fluxes were determined in surface soils (0–10 cm) at 4 sites supporting 1–2-year-old plantations of E. nitens. Net N mineralisation, nitrification, leaching, and uptake were measured by an in situ soil-core technique. Soils were derived from basalt (3 sites) or mudstone (1 site). Average rates of net N mineralisation ranged from 18 to 91 kg N/ha·year, and most mineralised N was nitrified and leached. There were significant linear relationships among net N mineralisation, nitrification, and leaching (r = 0·61–0·83). Annual rates of net N mineralisation varied as much within sites as between them, and rates in individual plots were significantly correlated with anaerobically mineralisable N (r = 0·82) or total N (r = 0·66), but were not correlated or only weakly correlated with C: N ratio, loss-on-ignition, organic C, water content, or temperature. Leaching was weakly correlated with effective rainfall (rainfall minus evaporation, r = 0·39). Soil contained most mineral N during February–April (i.e. late summer–early autumn) and least during October–November (i.e. late spring). We concluded that available N at these sites was highly variable spatially and temporally, and at a plot scale was closely related to concentrations of mineralisable substrate and not to soil water or temperature.

Plant uptake of nitrogen from the organic nitrogen fraction of animal manures: a laboratory experiment

2000 ◽  
Vol 134 (2) ◽  
pp. 159-168 ◽  
Author(s):  
D. R. CHADWICK ◽  
F. JOHN ◽  
B. F. PAIN ◽  
B. J. CHAMBERS ◽  
J. WILLIAMS
Keyword(s):  
N Mineralization ◽  
Organic N ◽  
Pig Slurry ◽  
Mineral N ◽  
N Content ◽  
Total N ◽  
N Supply ◽  
Ammonium N ◽  
Cow Slurry ◽  
N Fractions

Twenty slurries, 20 farmyard manures (FYM) and 10 poultry manures were chemically analysed to characterize their nitrogen (N) fractions and to assess their potential organic N supply. The organic N fraction varied between manure types and represented from 14% to 99% of the total N content. The readily mineralizable N fraction, measured by refluxing with KCl, was largest in the pig FYMs and broiler litters, but on average only represented 7–8% of the total N content. A pot experiment was undertaken to measure N mineralization from the organic N fraction of 17 of these manures. The ammonium-N content of the manures was removed and the remaining organic N mixed with a low mineral N status sandy soil, which was sown with perennial ryegrass (Lolium perenne L.). N offtake was used as a measure of mineralization throughout the 199 day experiment. The greatest N mineralization was measured from a layer manure and a pig slurry, where N offtake represented 56% and 37% of the organic N added, respectively. Lowest (%) N mineralization was measured from a dairy cow slurry (< 2%) and a beef FYM (6%). The mineralization rate was negatively related to the C[ratio ]organic N ratio of the ammonium-N stripped manures (P < 0·01, r = −0·63).

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