Dissolution rates of mineral nitrogen fertilisers : effects of moisture and precipitation
Hygroscopicity and deliquescence refer to the ability of a solid to absorb air moisture in which it dissolves and have long been recognised as properties having negative impacts on the product quality of explosives, pharmaceuticals, and fertilisers. Contrastingly, this thesis reconsiders and reap...
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| Formato: | H3 |
| Lenguaje: | Inglés sueco |
| Publicado: |
SLU/Dept. of Soil and Environment
2018
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| Materias: |
| _version_ | 1855572337922932736 |
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| author | Sigtryggsson, Christian |
| author_browse | Sigtryggsson, Christian |
| author_facet | Sigtryggsson, Christian |
| author_sort | Sigtryggsson, Christian |
| collection | Epsilon Archive for Student Projects |
| description | Hygroscopicity and deliquescence refer to the ability of a solid to absorb air moisture in
which it dissolves and have long been recognised as properties having negative impacts on
the product quality of explosives, pharmaceuticals, and fertilisers. Contrastingly, this thesis
reconsiders and reappraises the hygroscopic effects of common mineral fertilisers, proposing
hygroscopicity to beneficially enable quick dissolution under humid air conditions in absence
of precipitation. Although precision fertilisation has improved, little is known about
the dissolution dynamics of mineral nitrogen fertilisers in the field when exposed to either
moist air or precipitation. In this thesis, dissolution rates of fertilisers based on ammonium
nitrate (Axan™) and calcium nitrate (Kalksalpeter™), and of comparable pure salts, were
recorded in a hygroscopicity test (≥90 % relative humidity at 25°C). Furthermore, dissolution
rates of the fertilisers were also studied in a rain simulation (moderate intensity). In the
hygroscopicity test, the pure reference salts had a higher hygroscopicity and shorter dissolution
time relative the fertiliser products. The ammonium nitrate-based fertiliser and the
pure ammonium nitrate salt moreover had higher dissolution rates (completely dissolved
after 5.0 and 2.3 hours) compared to the corresponding calcium nitrate fertiliser and salt
(21.1 and 4.3 hours respectively). All compounds tested dissolved within 24 hours. Endothermic
properties, i.e. heat uptake during dissolution, seemed strongly correlated to the hygroscopic
rates recorded. According to a thermodynamic calculation made, strongly endothermic
salts had higher hygroscopicity compared to those with moderate or weak endothermic
properties. In the rain simulation, the ammonium nitrate and calcium nitrate-based
fertilisers required 5 and 6.5 mm of simulated precipitation, respectively. However, a theoretic
estimation suggested less water to be sufficient at optimal application. For highly soluble
fertilisers, the time during which the fertiliser is exposed to water may be more important
from a dissolution point of view than the solubility. Considering the dissolution rates
of fertilisers reported in this work, regardless if driven by hygroscopicity or precipitation,
the limiting factor in the fertilisation system does not seem to be the dissolution but the
dilution to concentrations non-toxic for crops. Future research should focus on the transport
of dissolved nitrogen in the soil, at different soil moisture levels. Thereby, the time for a dry
solid fertiliser to dissolve and reach the root zone of a crop could be better predicted. |
| format | H3 |
| id | RepoSLU14004 |
| institution | Swedish University of Agricultural Sciences |
| language | Inglés swe |
| publishDate | 2018 |
| publishDateSort | 2018 |
| publisher | SLU/Dept. of Soil and Environment |
| publisherStr | SLU/Dept. of Soil and Environment |
| record_format | eprints |
| spelling | RepoSLU140042019-02-26T14:08:38Z Dissolution rates of mineral nitrogen fertilisers : effects of moisture and precipitation Sigtryggsson, Christian hygroscopicity deliquescence fertilisers calcium nitrate ammonium nitrate dissolution rates rain simulation enthalpy precision fertilisation Hygroscopicity and deliquescence refer to the ability of a solid to absorb air moisture in which it dissolves and have long been recognised as properties having negative impacts on the product quality of explosives, pharmaceuticals, and fertilisers. Contrastingly, this thesis reconsiders and reappraises the hygroscopic effects of common mineral fertilisers, proposing hygroscopicity to beneficially enable quick dissolution under humid air conditions in absence of precipitation. Although precision fertilisation has improved, little is known about the dissolution dynamics of mineral nitrogen fertilisers in the field when exposed to either moist air or precipitation. In this thesis, dissolution rates of fertilisers based on ammonium nitrate (Axan™) and calcium nitrate (Kalksalpeter™), and of comparable pure salts, were recorded in a hygroscopicity test (≥90 % relative humidity at 25°C). Furthermore, dissolution rates of the fertilisers were also studied in a rain simulation (moderate intensity). In the hygroscopicity test, the pure reference salts had a higher hygroscopicity and shorter dissolution time relative the fertiliser products. The ammonium nitrate-based fertiliser and the pure ammonium nitrate salt moreover had higher dissolution rates (completely dissolved after 5.0 and 2.3 hours) compared to the corresponding calcium nitrate fertiliser and salt (21.1 and 4.3 hours respectively). All compounds tested dissolved within 24 hours. Endothermic properties, i.e. heat uptake during dissolution, seemed strongly correlated to the hygroscopic rates recorded. According to a thermodynamic calculation made, strongly endothermic salts had higher hygroscopicity compared to those with moderate or weak endothermic properties. In the rain simulation, the ammonium nitrate and calcium nitrate-based fertilisers required 5 and 6.5 mm of simulated precipitation, respectively. However, a theoretic estimation suggested less water to be sufficient at optimal application. For highly soluble fertilisers, the time during which the fertiliser is exposed to water may be more important from a dissolution point of view than the solubility. Considering the dissolution rates of fertilisers reported in this work, regardless if driven by hygroscopicity or precipitation, the limiting factor in the fertilisation system does not seem to be the dissolution but the dilution to concentrations non-toxic for crops. Future research should focus on the transport of dissolved nitrogen in the soil, at different soil moisture levels. Thereby, the time for a dry solid fertiliser to dissolve and reach the root zone of a crop could be better predicted. Ett ämnes hygroskopicitet och delikvescens är dess förmåga att absorbera fukt ur luften och lösa sig i denna, en egenskap som i regel förknippas med kvalitetsförsämringar hos sprängmedel, läkemedel och mineralgödselprodukter. Under nederbördsfattiga förhållanden med tillräcklig luftfuktighet kan hygroskopiska egenskaper hos ett gödselmedel ändå vara mycket fördelaktiga och medge en snabb upplösning, även vid avsaknad av regn. Även om precisionsgödsling utvecklats på senare tid saknas fortfarande kunskap kring gödselmedlens upplösning i fält vid exponering för fuktig luft eller nederbörd. I denna uppsats har upplösningshastigheter bestämts för mineralgödselmedel baserade på ammoniumnitrat (Axan™) och kalciumnitrat (Kalksalpeter™) samt två rena referenssalter i en hygroskopimätning (≥90 % relativ luftfuktighet vid 25°C). Upplösningshastigheter för gödselmedel har vidare studerats i en regnsimulering med måttlig intensitet. I hygroskopitestet hade de rena referenssalterna högre hygroskopicitet och kortare upplösningstid än gödselprodukterna. Vidare hade det ammoniumnitratbaserade gödselmedlet och det rena ammoniumnitratsaltet högre upplösningshastighet jämfört med motsvarande kalciumnitratbaserade produkt och salt. Samtliga gödselmedel och salter löstes upp genom hygroskopi inom 24 timmar under ovan givna förutsättningar. Resultaten indikerar vidare att endoterma egenskaper, dvs. upptag av värme under upplösningsfasen, är en viktig faktor kopplad till uppmätta hygroskopiciteter. En termodynamisk beräkning visar att starkt endoterma salter verkar ha högre hygroskopicitet än svagt till måttligt endoterma salter. I regnsimuleringen krävde den ammoniumnitratbaserade gödselprodukten 5 mm simulerad nederbörd och den kalciumnitratbaserade 6,5 mm. Trots det visade en teoretisk uppskattning att långt mindre nederbörd skulle kunna vara tillräckligt för upplösning vid optimal applicering. För gödselmedel med hög löslighet skulle tiden under vilken de exponeras för vatten kunna vara mer väsentlig i upplösningssynpunkt än själva lösligheten. Oavsett om upplösningen drivs av hygroskopicitet eller nederbörd tycks den begränsande faktorn i tillförseln av näring till grödan ej vara upplösningsfasen utan huruvida tillräcklig utspädning kan erhållas för att undvika toxiska koncentrationer. En uppföljande modell över transport och utspädning i markprofilen skulle behövas för att kunna uppskatta tiden från applicering av gödselmedlet på markytan till upptag i rotzonen. SLU/Dept. of Soil and Environment 2018 H3 eng swe https://stud.epsilon.slu.se/14004/ |
| spellingShingle | hygroscopicity deliquescence fertilisers calcium nitrate ammonium nitrate dissolution rates rain simulation enthalpy precision fertilisation Sigtryggsson, Christian Dissolution rates of mineral nitrogen fertilisers : effects of moisture and precipitation |
| title | Dissolution rates of mineral nitrogen fertilisers : effects of moisture and precipitation |
| title_full | Dissolution rates of mineral nitrogen fertilisers : effects of moisture and precipitation |
| title_fullStr | Dissolution rates of mineral nitrogen fertilisers : effects of moisture and precipitation |
| title_full_unstemmed | Dissolution rates of mineral nitrogen fertilisers : effects of moisture and precipitation |
| title_short | Dissolution rates of mineral nitrogen fertilisers : effects of moisture and precipitation |
| title_sort | dissolution rates of mineral nitrogen fertilisers : effects of moisture and precipitation |
| topic | hygroscopicity deliquescence fertilisers calcium nitrate ammonium nitrate dissolution rates rain simulation enthalpy precision fertilisation |