06 March 2023
Tionchar úiré chosanta ar an micribhithóim ithreach
Aoife Ní Dhuibh
Is gás ceaptha teasa cumhachtach é ocsaíd nítriúil le poitéinseal téimh dhomhanda i bhfad níos mó ná dé-ocsaíd charbóin, rud a dhéanann dochar don chiseal ózóin freisin. Féadann eotrófú agus sil-leagan aigéad a bheith mar thoradh ar astuithe amóinia, le tionchair dhiúltacha ar bhithéagsúlacht agus ar shláinte éiceachórais. In Éirinn, is ionann earnáil na talmhaíochta agus 92.2% den ocsaíd nítriúil agus beagnach gach astuithe amóinia. Uirlis amháin atá in úsáid faoi láthair chun na hastuithe seo a mhaolú is ea leasachán úiré cosanta a úsáid, ach tá sé tábhachtach measúnú a dhéanamh ar an tionchar ar an mbitheolaíocht ithreach bhunúsach chun na teicneolaíochtaí coisctheacha a chur i bhfeidhm ag leibhéal na feirme.
Tá sé léirithe ag taighde nua ó Chaisleán Bhaile Sheáin nach raibh aon tionchar ag coscaire úiréáis N-(n-bhúitile) tiafosfarach triaimíd (NBPT), a ionchorpraítear i leasachán úiré faoi chosaint, ar struchtúr agus ar fhlúirse na bpobal baictéarach agus fungais ithreach tar éis 5 bliana de chur i bhfeidhm arís agus arís eile ar thalamh féaraigh a ndéantar dianbhainistiú air. Léirigh an staidéar freisin gur fhan na pobail mhiocróbacha a raibh baint acu le timthriall nítrigine agus próisis claochlaithe cothaitheach gan athrú le húsáid an choscaire úiréáis. D’athraigh cur i bhfeidhm leasacháin, trí níotráit amóiniam cailciam (CAN), nó Úiré an struchtúr pobail fungais, ach ní raibh difríocht shuntasach idir an struchtúr pobail baictéarach i gceapacha leasacháin agus na ceapacha neamhleasaithe.
Cuireann coscairí úiréáis cosúil le N-(n-bhúitile) tiafosfarach triaimíd (NBPT) bac ar shuíomh gníomhach na heinsíme úiréáis, rud a mhaolaíonn luas comhshó úiré go hamóiniam san ithir, nó, ar ithir, a mbíonn caillteanais nítrigine laghdaithe agus éifeachtúlacht úsáide nítrigine níos fearr mar thoradh air. Roimhe seo, léirigh taighde ó Theagasc Chaisleán Bhaile Sheáin gur laghdaigh aistriú ó CAN go leasachán úiré cosanta fachtóirí astaíochta ocsaíd nítriúil 71% agus gur laghdaigh luaineacht amóinia 78.5%, agus ag an am céanna an táirgeacht féir a chothabháil. Chuir an obair seo roinnt athdhearbhaithe ar fáil maidir le bogadh ar aghaidh le huchtú úiré cosanta ag leibhéal na feirme.
The impact of protected urea on the soil microbiome
By Aoife Duff
Nitrous oxide is a potent greenhouse gas with a global warming potential much greater than carbon dioxide, which is also damaging to the ozone layer. Ammonia emissions can lead to eutrophication and acid depositions, with negative impacts on biodiversity and ecosystem health. In Ireland, the agriculture sector accounts for 92.2% of nitrous oxide and virtually all ammonia emissions. The use of protected urea fertiliser is one tool currently being employed to mitigate these emissions, but assessment of the impact on the underlying soil biology is important for implementation of the inhibitor technologies at farm level.
New research from Johnstown Castle has demonstrated that there was no impact of urease inhibitor N-(n-butyl) thiophosphoric triamide (NBPT), incorporated into protected urea fertiliser, on the structure and abundance of soil bacterial and fungal communities after 5 years of repeated application to an intensively managed grassland. The study further showed that the microbial communities involved in nitrogen cycling and nutrient transformation processes remained unchanged with the use of the urease inhibitor. Fertiliser application, either via calcium ammonium nitrate (CAN), or Urea did change the fungal community structure, but the bacterial community structure in fertilised plots was not significantly different from the unfertilised plots.
Urease inhibitors such as N-(n-butyl) thiophosphoric triamide (NBPT) block the active site of the urease enzyme thus moderating the speed of urea conversion to ammonium in, or, on soil, resulting in reduced nitrogen losses and greater nitrogen use efficiency. Previously, research from Teagasc Johnstown Castle has demonstrated that switching from CAN to protected urea fertiliser reduced nitrous oxide emission factors by 71% and reduced ammonia volatilisation by 78.5%, while maintaining grass yields. This work has provided some reassurance in moving forward with protected urea adoption at farm level.