CHANGES IN NATURAL 15N ABUNDANCE ASSOCIATED WITH PEDOGENIC PROCESSES IN SOIL. I. CHANGES ASSOCIATED WITH SALINE SEEPS

1980 ◽  
Vol 60 (2) ◽  
pp. 337-344 ◽  
Author(s):  
R. E. KARAMANOS ◽  
D. A. RENNIE
Keyword(s):  
Organic Nitrogen ◽  
Soil N ◽  
Soluble Salts ◽  
Recharge Area ◽  
Surface Samples ◽  
Nitrate N ◽  
Dominant Process ◽  
Pedogenic Processes ◽  
Very High ◽  
15N Abundance

The δa15N for the total and nitrate soil N from surface samples taken from recharge and discharge areas associated with a saline seep differ significantly. Suggested reasons for these differences are included. These data suggest that the nitrate moving towards the surface with the soluble salts is depleted in the heavier isotope; the very high δa15N for total and nitrate N of surface samples suggests that denitrification has been a dominant process operating in the saline seep area. Incubation studies carried out on Ap samples taken from the recharge and discharge areas have verified that the δa15N (and perhaps also the nature of the mineralizable organic nitrogen) from a "mature" and "recent" saline profile are different from each other, and distinctly different from that of the recharge area.

CHANGES IN NATURAL 15N ABUNDANCE ASSOCIATED WITH PEDOGENIC PROCESSES IN SOIL. II. CHANGES ON DIFFERENT SLOPE POSITIONS

1980 ◽  
Vol 60 (2) ◽  
pp. 365-372 ◽  
Author(s):  
R. E. KARAMANOS ◽  
D. A. RENNIE
Keyword(s):  
Total Nitrogen ◽  
Organic N ◽  
Total N ◽  
Nitrate N ◽  
Ammonium N ◽  
Soil Forming Processes ◽  
Pedogenic Processes ◽  
15N Abundance ◽  
Upper Slope

Rather marked variations in δa15N values were obtained in a study carried out on samples taken from four soils belonging to the Weyburn soil association. The δa15N of the total N of well-drained depressional profiles dropped sharply with depth and, in contrast, for upper slope positions was relatively constant to a depth of approximately 5 m. This characteristic enrichment in the heavier isotope of total nitrogen of surface horizons may represent long-term immobilization of partially oxidized ammonium N into the organic N fraction; δa15N of the total N more closely represents past soil-forming processes while that of the nitrate N appears to reflect, in addition, recent N cycle stresses.

Alkali investigations in the Sudan

1925 ◽  
Vol 15 (4) ◽  
pp. 407-419 ◽  
Author(s):  
A. F. Joseph
Keyword(s):  
Sodium Carbonate ◽  
Clay Soil ◽  
Salt Content ◽  
Sodium Sulphate ◽  
Water Soluble ◽  
Soluble Salts ◽  
Nile Water ◽  
Heavy Clay ◽  
Alkali Salts ◽  
Very High

(1) The cotton growing area in the Gezira consists of a heavy clay soil, the proportion of clay being about 50–60 per cent. in the upper layers with a maximum at about the 4th foot.(2) The water soluble salts amount to about 0·2 per cent. The proportion is highest at about the 3rd to 5th foot. The alkalinity (pH) is highest at the 2nd foot.(3) In the first 2 feet, the salts consist mainly of sodium carbonate and the third and fourth of sodium sulphate.(4) The irrigation (Blue Nile) water is of excellent quality as judged by its natural chemical composition. The concentrated water, however, contains a very high proportion of alkali salts. It is estimated that a season of normal irrigation would cause an increase of 0·01 per cent. in the alkali content of the first 4 feet of soil.(5) The sodium salts can readily act on the clay and the sodium clay so formed hydrolyses with the formation of sodium carbonate.(6) Samples taken at the same time from good and bad plots in the same area show a strong correlation between salt content and cropyielding power. There is also a correlation between pH and fertility.(7) In the same season and in the same area, virgin (i.e. unirrigated) plots give a higher yield than those which have been previously under the same system of cultivation.

Validation of NBudget for estimating soil N supply in Australia's northern grains region in the absence of soil test data

Soil Research ◽  
2017 ◽  
Vol 55 (6) ◽  
pp. 590 ◽  
Author(s):  
David F. Herridge
Keyword(s):  
Soil Water ◽  
Organic N ◽  
Soil N ◽  
Limited Information ◽  
Available N ◽  
Support Tool ◽  
Grain Yields ◽  
N Supply ◽  
Nitrate N ◽  
Winter Crop

Effective management of fertiliser nitrogen (N) inputs by farmers will generally have beneficial productivity, economic and environmental consequences. The reality is that farmers may be unsure of plant-available N levels in cropping soils at sowing and make decisions about how much fertiliser N to apply with limited information about existing soil N supply. NBudget is a Microsoft (Armonk, NY, USA) Excel-based decision support tool developed primarily to assist farmers and/or advisors in Australia’s northern grains region manage N. NBudget estimates plant-available (nitrate) N at sowing; it also estimates sowing soil water, grain yields, fertiliser N requirements for cereals and oilseed crops and N2 fixation by legumes. NBudget does not rely on soil testing for nitrate-N, organic carbon or soil water content. Rather, the tool relies on precrop (fallow) rainfall data plus basic descriptions of soil texture and fertility, tillage practice and information about paddock use in the previous 2 years. Use is made of rule-of-thumb values and stand-alone or linked algorithms describing, among other things, rates of mineralisation of background soil organic N and fresh residue N. Winter and summer versions of NBudget cover the 10 major crops of the region: bread wheat, durum, barley, canola, chickpea and faba bean in the winter crop version; sorghum, sunflower, soybean and mung bean in the summer crop version. Validating the winter crop version of NBudget estimates of sowing soil nitrate-N against three independent datasets (n=65) indicated generally close agreement between measured and predicted values (y=0.91x+16.8; r2=0.78). A limitation of the tool is that it does not account for losses of N from waterlogged or flooded soils. Although NBudget also predicts grain yields and fertiliser N requirements for the coming season, potential users may simply factor predicted soil N supply into their fertiliser decisions, rather than rely on the output of the tool. Decisions about fertiliser N inputs are often complex and are based on several criteria, including attitudes to risk, history of fertiliser use and costs. The usefulness and likely longevity of NBudget would be enhanced by transforming the current Excel-based tool, currently available on request from the author, to a stand-alone app or web-based tool.

THE ORIGIN OF HYDROCHEMICAL PATTERNS IN HUMMOCKY MORAINE

1967 ◽  
Vol 4 (6) ◽  
pp. 1065-1092 ◽  
Author(s):  
A. Rozkowski
Keyword(s):  
Groundwater Flow ◽  
Flow Model ◽  
Chemical Analyses ◽  
Soluble Salts ◽  
Recharge Area ◽  
Discharge Area ◽  
Transmission Zone ◽  
Significant Enrichment ◽  
Poorly Soluble ◽  
Shallow Zone

Hydrochemical investigations were carried out in a small local basin in hummocky moraine of southern Saskatchewan. The 'basin' consisted of a hill and surrounding permanent sloughs. The constructed Teledeltos flow model shows the typical pattern of groundwater flow near permanent lakes, where the hills are areas of recharge and the sloughs areas of discharge. Based on the chemical analyses of soil and till extracts as well as on the chemical analyses of slough and groundwater, the development of certain hydrochemical patterns in hummocky moraine can be explained.Three hydrochemical zones can be distinguished: SO4–Ca–Mg in the recharge area, SO4–Mg–Ca in the transmission zone, and SO4–Mg–(Na) in the discharge area. The increase of groundwater salinity from the recharge area to the discharge area is due to evapotranspiration as well as to the poor permeability of the glacial deposits.The SO4–Mg–Ca type of water of the recharge area is already formed in the zone of aeration. The subsequent changes of groundwater chemistry in the zone of saturation are induced by the enrichment of easily soluble salts and by the steady precipitation of poorly soluble salts. The sharp increase in salinity and the significant enrichment of the SO4–Mg type of water by easily soluble salts take place in the shallow zone of the discharge area close to the surface. The study of water extracts suggests the presence of groundwater discharge in the region of the capillary fringe of the recharge area also.The delivery of ions to the sloughs takes place by groundwater flow and inter-flow; therefore, the hydrochemistry of sloughs is primarily determined by the chemistry of these waters. The further metamorphosis of slough water is produced mainly by intensive evaporation as well as by ion exchange within the slough.

Role of dissolved organic nitrogen (DON) in soil N cycling in grassland soils

2004 ◽  
Vol 36 (5) ◽  
pp. 749-756 ◽  
Author(s):  
David L. Jones ◽  
David Shannon ◽  
Daniel V. Murphy ◽  
John Farrar
Keyword(s):  
Dissolved Organic Nitrogen ◽  
Organic Nitrogen ◽  
N Cycling ◽  
Soil N ◽  
Grassland Soils

Relationship of the Illinois soil nitrogen test to spring wheat yield and response to fertilizer nitrogen

2008 ◽  
Vol 88 (5) ◽  
pp. 837-848 ◽  
Author(s):  
S J Steckler ◽  
D J Pennock ◽  
F L Walley
Keyword(s):  
Soil Nitrogen ◽  
Crop Yields ◽  
Wheat Yield ◽  
N Fertilizer ◽  
Yield Response ◽  
Regression Equations ◽  
Soil N ◽  
Fertilizer N ◽  
Available N ◽  
Nitrate N

The Illinois soil N test (ISNT) has been used to distinguish between soils that are responsive and non-responsive to fertilizer N in Illinois. We examined the suitability of this test, together with more traditional measures of soil fertility, including spring nitrate-N and soil organic carbon (SOC), for predicting yield and N fertilizer response of wheat (Triticum aestivum) on hummocky landscapes in Saskatchewan. The relationship between ISNT-N and wheat yield and fertilizer N response was assessed using data and soils previously collected for a variable-rate fertilizer study. Soils were re-analyzed for ISNT-N. Our goal was to determine if ISNT-N could be used to improve the prediction of crop yields. Although ISNT-N was correlated with both unfertilized wheat yield (r = 0.467, P = 0.01) and fertilizer N response (r = -0.671, P = 0.01) when data from all study sites were combined, correlations varied according to landscape position and site. Stronger correlations between nitrate-N and both unfertilized wheat yield (r = 0.721, P = 0.01) and fertilizer N response (r = -0.690, P = 0.01) indicated that ISNT-N offered no advantage over nitrate-N. Although both tests broadly discriminated between sites with high or low N fertility, few relationships were detected on a point-by-point basis within a field. Stepwise regression equations predicting yield and yield response did not include ISNT-N, due in part to the high degree of collinearity between ISNT-N and other variables such as SOC, suggesting that ISNT-N alone was not a key indicator of soil N supply. Key words: Illinois soil nitrogen test, potentially available N, soil N, fertilizer N recommendations

scholarly journals Landslide Erosion Rate in the Eastern Cordillera of Northern Bolivia

2007 ◽  
Vol 11 (19) ◽  
pp. 1-30 ◽  
Author(s):  
Troy A. Blodgett ◽  
Bryan L. Isacks
Keyword(s):  
Erosion Rate ◽  
Aerial Photographs ◽  
Field Surveys ◽  
Bedrock Rivers ◽  
Eastern Cordillera ◽  
Erosion Rates ◽  
Landslide Volume ◽  
Tectonically Active ◽  
Dominant Process ◽  
Very High

Abstract The northeastern edge of the Bolivian Eastern Cordillera is an example of a tectonically active plateau margin where orographically enhanced precipitation facilitates very high rates of erosion. The topography of the steepest part of the margin exhibits the classic signature of high erosion rates consisting of high-relief V-shaped valleys where landsliding is the dominant process of hillslope erosion and bedrock rivers are incising into the landscape. The authors mapped landslide scars on multitemporal aerial photographs to estimate hillslope erosion rates. Field surveys of landslide scars are used to calibrate a landslide volume versus area relationship. The mapped area of landsliding, in combination with an estimate of the time for landslide scars to revegetate, leads to an erosion rate estimate. The estimated revegetation time, 10–35 yr, is based on analysis of multitemporal aerial photographs and tree rings. About 4%–6% of two watersheds in the region considered were affected by landslides over the last 10–35 yr. This result implies an erosion rate of 9 ± 5 mm yr−1 assuming that 90% of a single landslide reaches the river on average. Classified Landsat Thematic Mapper images show that landslides are occurring at approximately the same rate all across an approximately 40-km-wide swath within the high-relief zones of the cordillera.

Dissolved carbon and nitrogen leaching following variable logging-debris retention and competing-vegetation control in Douglas-fir plantations of western Oregon and Washington

2009 ◽  
Vol 39 (8) ◽  
pp. 1484-1497 ◽  
Author(s):  
Robert A. Slesak ◽  
Stephen H. Schoenholtz ◽  
Timothy B. Harrington ◽  
Brian D. Strahm
Keyword(s):  
Soil Water ◽  
Dissolved Organic Nitrogen ◽  
Organic Nitrogen ◽  
Total N ◽  
Vegetation Control ◽  
Dissolved Carbon ◽  
Competing Vegetation ◽  
Nitrate N ◽  
N Concentration ◽  
C And N

We examined the effect of logging-debris retention and competing-vegetation control (CVC, initial or annual applications) on dissolved organic carbon (DOC), dissolved organic nitrogen, and nitrate-N leaching to determine the relative potential of these practices to contribute to soil C and N loss at two contrasting sites. Annual CVC resulted in higher soil water nitrate-N concentration and flux, with the magnitude and duration of the effect greatest at the high-N site. Most of the increase in nitrate-N at the low-N site occurred in treatments where logging debris was retained. Dissolved organic nitrogen increased at the high-N site in March of each year following annual CVC, but the contribution of this increase to total N concentration was small (2%–4% of total N flux). There was no effect of logging-debris retention or CVC treatment on soil water DOC concentrations, indicating that DOC inputs from logging debris and competing vegetation were either retained or consumed in the mineral soil. The estimated increase in leaching flux of dissolved C and N associated with the treatments was low relative to total soil pools, making it unlikely that loss of these elements via leaching will negatively affect future soil productivity at these sites.

scholarly journals Potential relationships between exposure to arsenic (As) in the environment and endemic disease in southwestern China

2021 ◽  
Author(s):  
Donglin Li ◽  
Hucai Zhang ◽  
Fengqin Chang ◽  
Lizeng Duan ◽  
Yang Zhang
Keyword(s):  
Black Shale ◽  
Prevalence Rate ◽  
Human Exposure ◽  
Yunnan Province ◽  
Environmental Geochemistry ◽  
Soil Samples ◽  
Southwestern China ◽  
Soil N ◽  
Exposure Pathways ◽  
Very High

Abstract There have been many reported cases of a strange disease exhibiting clinical features of limb gangrene, blisters, ulceration and exfoliation in Daping village, Yunnan Province in southwestern China. The prevalence rate of the disease is very high compared to other places in Yunnan Province and greater China. The pathogenesis is unknown and has bewildered doctors for many years. In this study, the content of As in soil (n=31) , water (n=55) , and plants (n=7) were systematically measured. The results show a high As concentration in plants and soil samples from the area, and the source of As linked to the weathering of black shale strata. We assessed the risks of human exposure to As through six possible exposure pathways. Ingestion of soil and plants are found to be the two main ways that children and adults are exposed to As, and children have a higher health risk than adults. Our study sheds new light on the environmental geochemistry and health links of this disease.

Sign in / Sign up

Export Citation Format

Share Document