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IJAFR, volume 52, no1, 2013 >

Please use this identifier to cite or link to this item: http://hdl.handle.net/11019/448

Title: Seasonality of nitrogen uptake, apparent recovery of fertilizer nitrogen and background nitrogen supply in two Irish grassland soils
Authors: Murphy, P. N. C.
O'Connell, K.
Watson, S.
Watson, C. J.
Humphreys, James
Keywords: Apparent recovery of fertilizer nitrogen
Fertilizer nitrogen for grass
Nitrogen mineralisation
Nitrogen uptake
Seasonality of nitrogen uptake
Issue Date: 2013
Publisher: Teagasc (Agriculture and Food Development Authority), Ireland
Citation: P.N.C. Murphy, K. O’Connell, S. Watson, C.J. Watson, J. Humphreys. Seasonality of nitrogen uptake, apparent recovery of fertilizer nitrogen and background nitrogen supply in two Irish grassland soils. Irish Journal of Agricultural and Food Research, 2013, 52, 17–38
Series/Report no.: Irish Journal of Agricultural and Food Research;vol 52
Abstract: Improving fertilizer nitrogen (N) use efficiency is central to sustainable and profitable grassland agriculture. A plot experiment with a control and fertilizer N (calcium ammonium nitrate, 25–50 kg/ha N) applied on nine occasions from February to September 2002 was conducted at two sites in southwest Ireland to assess N uptake and apparent recovery of fertilizer N (ARFN). Apparent recovery of fertilizer N after eight weeks varied from low in February (21%) and March (46%) to high from April to August (69–98%), indicating that high N use efficiency can be achieved in Irish grasslands at these times. Low recovery in spring suggested that N was applied in excess of immediate crop requirements. Note that N uptake and ARFN values from this study are likely to be somewhat conservative, particularly for spring applications. Over the 8 weeks during which growth was monitored, most (70%) of the grass yield and N uptake response to fertilizer N were in weeks 1 to 4 after application; however, a significant (30%) response occurred in weeks 5–8. This suggested that residual N availability following grazing at 4 weeks can be significant and that there may be scope to decrease N application rates in a grazing rotation. This can potentially improve N use efficiency and decrease N surpluses, with associated economic and environmental benefits. Apparent recovery of fertilizer N was closely related to soil temperature, with a 5.8% increase in ARFN with a 1 °C increase in temperature. Background (non-fertilizer) N supply contributed an average of 164 kg/ha per year (49%) taken up by the fertilized sward, highlighting the potential importance of soil N mineralisation to grassland productivity. Note that these results are for one year at two sites and that conditions may vary between years and at other sites and also that the experiment did not reproduce the cumulative effect of repeated fertilizer application over the grazing year.
Description: peer-reviewed
URI: http://hdl.handle.net/11019/448
ISSN: 0791-6833
Appears in Collections:Livestock Systems
IJAFR, volume 52, no1, 2013

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