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.

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.

Dissolved organic nitrogen contributes significantly to leaching from furrow-irrigated cotton–wheat–maize rotations

Soil Research ◽  
2017 ◽  
Vol 55 (1) ◽  
pp. 70 ◽  
Author(s):  
B. C. T. Macdonald ◽  
A. J. Ringrose-Voase ◽  
A. J. Nadelko ◽  
M. Farrell ◽  
S. Tuomi ◽  
...  
Keyword(s):  
Soil Surface ◽  
Significant Loss ◽  
Organic N ◽  
Irrigated Agriculture ◽  
Cotton Production ◽  
N Loss ◽  
Deep Drainage ◽  
Mineral N ◽  
Undisturbed Soil ◽  
Total N

Leaching of nitrogen (N) in intensive irrigated agriculture can be a significant loss pathway. Though many studies have focussed on losses of mineral N, and in particular nitrate, dissolved organic N (DON) has received less coverage. In the present study, over a 5-year period (2008–2013), 740kgNha–1 fertiliser was applied to an irrigated cotton–wheat–maize rotation on a cracking clay (grey Vertosol). Deep drainage from the undisturbed soil profile at the site was measured at 2.1m below the soil surface using a variable tension lysimeter. In total, 108mm of drainage occurred during the 5 years and the majority of the drainage and the irrigations occurred during the cotton seasons. The majority of the N loss occurred during the first 3–4 irrigations and neither the N loss nor its composition were affected by the product or timing of the fertiliser application. The N in the drainage was composed of 12.8kgNOx-Nha–1, 8.7 DON-N and 0.1 NH4+-Nkgha–1, which shows that DON is an important component (40%) of the deep drainage N from irrigated Vertosol cotton production systems. Overall the total N flux lost via deep drainage represents 3% of the applied N fertiliser.

The influence of the soil matrix on nitrogen mineralisation and nitrification. II. The pore system as a framework for mapping the organisation of the soil matrix

Soil Research ◽  
1998 ◽  
Vol 36 (5) ◽  
pp. 855 ◽  
Author(s):  
D. T. Strong ◽  
P. W. G. Sale ◽  
K. R. Helyar
Keyword(s):  
Organic Matter ◽  
Pore Size ◽  
Organic N ◽  
Strong Positive Correlation ◽  
Pore System ◽  
Undisturbed Soil ◽  
Soil Matrix ◽  
Terminal Electron Acceptor ◽  
Microbial Decomposition ◽  
Organic C

Large numbers of small undisturbed soil volumes (1·7 cm3 ) were collected from the surface layer of a 2 m by 3 m field plot on a red earth near Wagga Wagga, New South Wales. The hypothesis tested was that an analysis of relationships between the volume of different pore size classes and various soil properties, measured on these soil volumes, can provide an understanding of soil organisation within the framework of the pore system. Three discrete findings were presented in confirmation of the hypothesis. (1) A non-uniform distribution of organic N through the pore system was indicated by the data analysis. Soil organic N tended to be concentrated in pores <0·6 µm and in pores 10-30 µm, but not in the intermediate pore size class (pores 0·6-10 µm). Concentrations of organic N in pores <0·6 µm are probably because of physical protection from microbial decomposition, but concentrations of organic N in pores 10-30 µm are probably because these pores are infrequently water-filled, and this limits bacterial activity more severely than in the pores 0·6-10 µm. Currently available assays for potentially mineralisable N cannot account for the effect of substrate location within the pore system, and a characterisation of the soil for the distribution of N in pores may enhance their utility. Soil disturbance is likely to alter organic matter distribution through the pore system and alter mineralisation dynamics. (2) Observations of pore size distributions before and after wetting suggested that soils which were high in organic matter and clay tended to have a greater volume of pores 0 ·6-30 µm which are unstable to drying and rewetting. It is proposed that these unstable pores 0 ·6-30 µm had been produced by the movement and alignment of clay particles during the growth of microbial colonies. (3) The volume of pores <0·6 µm had a relatively strong negative correlation with pH and a relatively strong positive correlation with Mn2+ . A mechanism based on redox chemistry principles was proposed to explain these relationships. It was suggested that the volume of pores <0·6 µm is related to the potential anaerobicity of the soil volume. In anaerobic conditions, the terminal electron acceptor for organic C oxidation may be MnO2 instead of O2, and in these circumstances, considerably more H+ would be consumed than in aerobic conditions. It is suggested that this alkaline effect extends into regions of the matrix where N mineralisation and nitrification are occurring, and stimulates these processes. The greater nitrification which may result from such a chain of events may, over time, effect greater acidification in those soil volumes which have greater microporosity.

Nitrogen leaching from soil lysimeters irrigated with dairy shed effluent and having managed drainage

Soil Research ◽  
2001 ◽  
Vol 39 (2) ◽  
pp. 385 ◽  
Author(s):  
P. L. Singleton ◽  
C. D. A McLay ◽  
G. F. Barkle
Keyword(s):  
Water Table ◽  
Soil Surface ◽  
World Health ◽  
Organic N ◽  
Similar Proportion ◽  
N Leaching ◽  
Undisturbed Soil ◽  
Total N ◽  
Leaching Losses ◽  
N Form

The leaching of nitrogen (N) from agricultural soils is undesirable for environmental and health reasons. We investigated the effects of adding dairy shed effluent (DSE), irrigated on a weekly basis during the milking season, on the amounts and forms of N leached from large undisturbed soil monolith lysimeters of a Gley Soil over a period of 2 years. Drainage was managed using a weir that maintained the water table at 3 depths: 25 (high), 50 (medium), or 75 (low) cm below the soil surface. The low water table treatment represented the usual situation for the soil when drained. If undrained, it would be usual during wet periods in the field for a perched water table to form on the slowly permeable horizon at 75 cm depth. The total amount of N irrigated onto the lysimeters in the first milking season was equivalent to a total of 511 kg N/ha.year, and up to 33.3 kg N/ha.year leached from the soil. The losses from lysimeters receiving effluent were nearly double those from lysimeters receiving an equivalent amount of water only, when the high and medium water tables were imposed. Adding effluent caused only a small increase (7 kg N/ha) in total N leached in the low drainage treatment. In the second milking season, the effluent-N loading was increased to 1518 kg N/ha.year and the pasture was managed to simulate a ‘cut and carry’ land treatment system. Under these conditions, up to 131.4 kg N/ha.year leached from the soil, which was nearly 100 kg N/ha more than lysimeters receiving only water. The total N leaching losses represented a similar proportion of added N (7% and 9%) for years 1 and 2, respectively. Most of the leached N (80—90%) was in organic N form. The managed drainage treatment in which the water table was nearest the soil surface resulted in less N being leached in the nitrate-N (NO 3 -N) form (<2.5 kg N/ha.year) than the other drainage treatments (6—12 kg N/ha.year); however, it did result in the greatest amount of organic and total N leached (33 and 131 kg N/ha for Year 1 and 2, respectively). The smaller amount of NO 3 -N leached from the high water table treatment is attributed to enhanced denitrification, and the greater amount of organic N is attributed to preferential flow. Although NO 3 -N concentrations in leachate generally remained below World Health Organisation (WHO) standards in all treatments, the large amount of N leached in organic form would suggest that inorganic N should not be the only form of N considered when measuring N leaching losses.

Predicting nitrogen mineralisation in Australian irrigated cotton cropping systems

Soil Research ◽  
2019 ◽  
Vol 57 (3) ◽  
pp. 247 ◽  
Author(s):  
Richard Brackin ◽  
Scott Buckley ◽  
Rhys Pirie ◽  
Francois Visser
Keyword(s):  
Cropping Systems ◽  
Farming Systems ◽  
Total Carbon ◽  
Ex Situ ◽  
Organic N ◽  
N Mineralisation ◽  
Total N ◽  
Agricultural Industries ◽  
Mineralisation Potential

Cotton cropping systems in Australia have poor nitrogen (N) use efficiency, largely due to over-application of N fertiliser. The N mineralisation from soil organic N reserves is often overlooked, or underestimated despite recent studies indicating that it may contribute the majority of N exported with the crop. Predicting N mineralisation is a major challenge for agricultural industries worldwide, as direct measurements are time-consuming and expensive, but there is considerable debate as to the most reliable methods for indirect estimation. Additionally, laboratory incubations assess potential (rather than actual) mineralisation, and may not be representative of N cycling rates in the field. We collected 177 samples from most major Australian cotton growing regions, and assessed their mineralisation potential using ex situ laboratory incubations, along with an assessment of potential indicators routinely measured in soil nutrient tests. Additionally, at three unfertilised sites we conducted in situ assessment of mineralisation by quantifying soil N at the beginning of the growing season, and soil and crop N at the end of the season. We found that Australian cotton cropping soils had substantial mineralisation potential, and that soil total N and total carbon were correlated with mineralisation, and have potential to be used for prediction. Other potential indicators such as carbon dioxide production and ammonium and nitrate concentrations were not correlated with mineralisation. In parallel studies of ex situ and in situ mineralisation, we found ex situ laboratory incubations overestimated mineralisation by 1.7 times on average. We discuss findings in terms of management implications for Australian cotton farming systems.

scholarly journals Nitrogen fertilizer value of animal slurries with different proportions of liquid and solid fractions: A 3-year study under field conditions

2021 ◽  
pp. 1-11
Author(s):  
Betina Nørgaard Pedersen ◽  
Bent T. Christensen ◽  
Luca Bechini ◽  
Daniele Cavalli ◽  
Jørgen Eriksen ◽  
...  
Keyword(s):  
Solid Fraction ◽  
Liquid Fraction ◽  
N Fertilizer ◽  
Organic N ◽  
First Year ◽  
Net N Mineralization ◽  
Pig Slurry ◽  
Total N ◽  
Plant Availability ◽  
Loamy Sand Soil

Abstract The plant availability of manure nitrogen (N) is influenced by manure composition in the year of application whereas some studies indicate that the legacy effect in following years is independent of the composition. The plant availability of N in pig and cattle slurries with variable contents of particulate matter was determined in a 3-year field study. We separated cattle and a pig slurry into liquid and solid fractions by centrifugation. Slurry mixtures with varying proportions of solid and liquid fraction were applied to a loamy sand soil at similar NH4+-N rates in the first year. Yields and N offtake of spring barley and undersown perennial ryegrass were compared to plots receiving mineral N fertilizer. The first year N fertilizer replacement value (NFRV) of total N in slurry mixtures decreased with increasing proportion of solid fraction. The second and third season NFRV averaged 6.5% and 3.8% of total N, respectively, for cattle slurries, and 18% and 7.5% for pig slurries and was not related to the proportion of solid fraction. The estimated net N mineralization of residual organic N increased nearly linearly with growing degree days (GDD) with a rate of 0.0058%/GDD for cattle and 0.0116%/GDD for pig slurries at 2000–5000 GDD after application. In conclusion NFRV of slurry decreased with increasing proportion of solid fraction in the first year. In the second year, NFRV of pig slurry N was significantly higher than that of cattle slurry N and unaffected by proportion between solid and liquid fraction.

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.

scholarly journals Evidence of Phosphate Mining and Agriculture Influence on Concentrations, Forms, and Ratios of Nitrogen and Phosphorus in a Florida River

Water ◽  
2021 ◽  
Vol 13 (8) ◽  
pp. 1064
Author(s):  
Shuiwang Duan ◽  
Kamaljit Banger ◽  
Gurpal S. Toor
Keyword(s):  
Agricultural Land ◽  
Water Discharge ◽  
Mining Area ◽  
Specific Conductance ◽  
Organic N ◽  
Wet Season ◽  
Nitrogen And Phosphorus ◽  
Total N ◽  
Phosphate Mining ◽  
Molar Ratios

Florida has a long history of phosphate-mining, but less is known about how mining affects nutrient exports to coastal waters. Here, we investigated the transport of inorganic and organic forms of nitrogen (N) and phosphorus (P) over 23 sampling events during a wet season (June–September) in primary tributaries and mainstem of Alafia River that drains into the Tampa Bay Estuary. Results showed that a tributary draining the largest phosphate-mining area (South Prong) had less flashy peaks, and nutrients were more evenly exported relative to an adjacent tributary (North Prong), highlighting the effectiveness of the mining reclamation on stream hydrology. Tributaries draining > 10% phosphate-mining area had significantly higher specific conductance (SC), pH, dissolved reactive P (DRP), and total P (TP) than tributaries without phosphate-mining. Further, mean SC, pH, and particulate reactive P were positively correlated with the percent phosphate-mining area. As phosphate-mining occurred in the upper part of the watershed, the SC, pH, DRP, and TP concentrations increased downstream along the mainstem. For example, the upper watershed contributed 91% of TP compared to 59% water discharge to the Alafia River. In contrast to P, the highest concentrations of total N (TN), especially nitrate + nitrite (NOx–N) occurred in agricultural tributaries, where the mean NOx–N was positively correlated with the percent agricultural land. Dissolved organic N was dominant in all streamwaters and showed minor variability across sites. As a result of N depletion and P enrichment, the phosphate-mining tributaries had significantly lower molar ratios of TN:TP and NOx–N:DRP than other tributaries. Bi-weekly monitoring data showed consistent increases in SC and DRP and a decrease in NOx–N at the South Prong tributary (highest phosphate-mining area) throughout the wet season, and different responses of dissolved inorganic nutrients (negative) and particulate nutrients (positive) to water discharge. We conclude that (1) watersheds with active and reclaimed phosphate-mining and agriculture lands are important sources of streamwater P and N, respectively, and (2) elevated P inputs from the phosphate-mining areas altered the N:P ratios in streamwaters of the Alafia River.

Characteristics of Non-Point Source N Export via Surface Runoff from Sloping Croplands in Northeast China

2011 ◽  
Vol 347-353 ◽  
pp. 2302-2307 ◽  
Author(s):  
Hong Xiang Wang ◽  
Yi Shi ◽  
Jian Ma ◽  
Cai Yan Lu ◽  
Xin Chen
Keyword(s):  
Point Source ◽  
Surface Runoff ◽  
Rainfall Intensity ◽  
Inorganic Nitrogen ◽  
Rainfall Amount ◽  
Organic N ◽  
Dissolved Inorganic Nitrogen ◽  
Slope Gradient ◽  
N Loss ◽  
Total N

A field experiment was conducted to study the characteristics of non-point source nitrogen (N) in the surface runoff from sloping croplands and the influences of rainfall and cropland slope gradient. The results showed that dissolved total N (DTN) was the major form of N in the runoff, and the proportion occupied by dissolved inorganic nitrogen (DIN) ranged from 45% to 85%. The level of NH4+-N was generally higher than the level of NO3--N, and averaged at 2.50 mg·L-1and 1.07 mg·L-1respectively. DIN was positively correlated with DTN (R2=0.962). Dissolved organic N (DON) presented a moderate seasonal change and averaged at 1.40 mg·L-1. Rainfall amount and rainfall intensity significantly affected the components of DTN in the runoff. With the increase of rainfall amount and rainfall intensity, the concentrations of DTN, NH4+-N and NO3--N presented a decreased trend, while the concentration of DON showed an increased trend. N loss went up with an increase in the gradient of sloping cropland, and was less when the duration was longer from the time of N fertilization.fertilization.

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