Measurement and simulation of anion diffusion in natural soil aggregates and clods

Addiscott, T. M.; Thomas, Victor H.; Janjua, M. A.

doi:10.1111/j.1365-2389.1983.tb01066.x

Cited by 25 publications

(7 citation statements)

References 20 publications

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“…Movement of Br could be due to the mass transfer or diffusion. However, according to Addiscott et al (1983), the average value of the diffusion coefficient (D) for Br in soil is equal to 1.08 Â 10 À 5 cm 2 /s. Therefore, it is unlikely that the movement of Br in the samples was due to diffusion.…”

Section: Transport Of Br With the Impregnating Materialsmentioning

confidence: 99%

Submicroscopic measurements of tracer distribution related to surface features of soil aggregates

Nobles¹,

Wilding²,

McInnes³

2004

Geoderma

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Section: Transport Of Br With the Impregnating Materialsmentioning

confidence: 99%

Submicroscopic measurements of tracer distribution related to surface features of soil aggregates

Nobles¹,

Wilding²,

McInnes³

2004

Geoderma

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“…A further change involves nitrate movement between the phases, which was originally assumed to equalize their concentrations. Because this movement occurs by diffusion, equalization does not occur completely and to allow for this the model can now use 'holdback' factors based on measurements of intraaggregate nitrate diffusion (Addiscott, Thomas & Janjua, 1983). Upward movement of water due to evaporation at the soil stirface occurs through both phases simultaneously and carries nitrate with it.…”

Section: The Submodels Nitrate Leachingmentioning

confidence: 99%

Computer simulation of changes in soil mineral nitrogen and crop nitrogen during autumn, winter and spring

1987

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The computer model described simulates changes in soil mineral nitrogen and crop uptake of nitrogen by computing on a daily basis the amounts of N leached, mineralized, nitrified and taken up by the crop. Denitrification is not included at present. The leaching submodel divides the soil into layers, each of which contains mobile and immobile water. It needs points from the soil moisture characteristic, measured directly or derived from soil survey data; it also needs daily rainfall and evaporation. The mineralization and nitrification submodel assumes pseudo-zero order kinetics and depends on the net mineralization rate in the topsoil and the daily soil temperature and moisture content, the latter being computed in the leaching submodel. The crop N uptake and dry-matter production submodel is a simple function driven by degree days of soil temperature and needs in addition only the sowing date and the date the soil returns to field capacity, the latter again being computed in the leaching submodel. A sensitivity analysis was made, showing the effects of 30% changes in the input variables on the simulated amounts of soil mineral N and crop N present in spring when decisions on N fertilizer rates have to be made. Soil mineral N was influenced most by changes in rainfall, soil water content, mineralization rate and soil temperature, whilst crop N was affected most by changes in soil temperature, rainfall and sowing date. The model has so far been applied only to winter wheat growing through autumn, winter and spring but it should be adaptable to other crops and to a full season.The model was validated by comparing its simulations with measurements of soil mineral N, dry matter and the amounts of N taken up by winter wheat in experiments made at seven sites during 5 years. The simulations were assessed graphically and with the aid of several statistical summaries of the goodness of fit. The agreement was generally very good; over all years 72 % of all simulations of soil mineral N to 90 cm depth were within 20 kg N/ha of the soil measurements; also 78 % of the simulations of crop nitrogen uptake were within 15 kg N/ha and 63% of the simulated yields of dry matter were within 25 g/m 2 of the amounts measured. All correlation coefficients were large, positive, and highly significant, and on average no statistically significant differences were found between simulation and measurement either for soil mineral N or for crop N uptake. c r o P t o w n i°n '* w a s applied seems very variable. Powlson et al. (1983) found it to range from 51 to In 1985 farmers in England and Wales used nearly 84% in field experiments on winter wheat spread 1-3 million tonnes of fertilizer nitrogen, of which over 3 years. With spring barley, Dowdell et al. roughly 350000, worth over £100 million, went to (1984) found values between 46 and 54% in lysimeter winter wheat (C. D. Kershaw, private communica-experiments. Quite a lot of the unused N will be tion). Although cereals are relatively efficient users immobilized in soil organic matter an...

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“…Em condições de maior permanência da água da chuva ou da irrigação, o nitrogênio adicionado ao solo pode difundir-se para o interior dos agregados maiores, circunstâncias em que, apesar das restrições na absorção do nutriente pela planta e do aumento do processo de desnitrificação, a lixiviação do nitrogênio na forma de nitrato pode ser bastante reduzida (Wiersum, 1962;Addiscott et al, 1983).…”

Section: Introductionunclassified

Transporte do amônio em colunas com agregados de um latossolo vermelho distrófico

Coelho¹,

Ruíz²,

Ferreira³

et al. 2000

Rev. bras. eng. agríc. ambient.

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RESUMOPara descrever o transporte do íon amônio em diferentes classes de agregados de um Latossolo Vermelho distrófico realizou-se um experimento de laboratório cujos tratamentos corresponderam a um fatorial 3 x 5, sendo: três fontes de NH 4 + [(NH 4 ) 2 SO 4 , NH 4 Cl e NH 4 NO 3 ] e cinco classes de agregados (2,0-1,0; 1,0-0,5; 0,5-0,25; 0,25-0,105; e <0,105 mm). A unidade experimental foi constituída de uma coluna de vidro saturada, sob vácuo, com uma solução de CaCl 2 0,005 mol L -1. Aplicou-se, a seguir, a solução saturante até percolação constante, seguida de um pulso de sete volumes de poros da respectiva fonte a 0,01 mol L concentrations were determined (C). C/C o relationships were calculated for every p fraction, and the experimental elution curves were traced. The highest retardation factors were calculated for the smallest aggregates, indicating a larger retention of ammonium, and the almost superimposed theoretical curves showed the predominance of the dispersive transport for ammonium. The NH 4 + percolation was not affected by the studied anions in the different aggregates classes.

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Measurement and simulation of anion diffusion in natural soil aggregates and clods

Cited by 25 publications

References 20 publications

Submicroscopic measurements of tracer distribution related to surface features of soil aggregates

Submicroscopic measurements of tracer distribution related to surface features of soil aggregates

Computer simulation of changes in soil mineral nitrogen and crop nitrogen during autumn, winter and spring

Transporte do amônio em colunas com agregados de um latossolo vermelho distrófico

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