Quantifying the effect of nitrogen on productivity of cocksfoot (Dactylis glomerata L.) pastures |
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| Authors: | A Mills DJ Moot PD Jamieson |
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| Institution: | 1. Agriculture and Life Sciences Division, Lincoln University, PO Box 84, Canterbury 7647, New Zealand;2. Crop & Food Research, Private Bag 4704, Christchurch 8140, New Zealand;1. EEA INTA Marcos Juárez, Ruta 12 s/n (2580), Marcos Juárez, Córdoba, Argentina;2. Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Argentina;3. Cátedra de Cerealicultura, Facultad de Agronomía, Universidad de Buenos Aires, Av. San Martín 4453, C1417DSE Buenos Aires, Argentina;4. IFEVA, Universidad de Buenos Aires, Av. San Martín 4453, C1417DSE Buenos Aires, Argentina;1. Norwegian Institute of Bioeconomy Research, 4353 Klepp Stasjon, Norway;2. CEH-Edinburgh, Bush Estate, Penicuik EH26 0QB, United Kingdom;1. Animal and Grassland Research and Innovation Center, Teagasc Moorepark, Fermoy, Co. Cork, Ireland;2. School of Agriculture, Food Science & Veterinary Medicine, University College Dublin, Belfield, Dublin 4, Ireland;3. INRA, AgroCampus Ouest, UMR 1348, Physiologie, Environnement et Génétique pour l''Animal et les Systèmes d''Elevage, F-35590 Saint-Gilles, France;1. Department of Crop and Forest Sciences and AGROTECNIO (Center for Research in Agrotechnology), University of Lleida, Av. Rovira Roure 191, 25198 Lleida, Spain;2. ICREA, Catalonian Institution for Research and Advanced Studies, Spain |
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| Abstract: | Inorganic nitrogen fertilisers are commonly applied to crops and pastures to increase or maintain productivity. The benefits of N application must be balanced with the potential for environmental damage. At Lincoln University, Canterbury, New Zealand a split plot experiment with two irrigation levels (irrigated and dryland) and two N fertiliser application rates (0 and 800 kg N/ha/y (2003/2004) or 1600 kg N/ha/y (2004/2005) was established on a 9-year-old cocksfoot (Dactylis glomerata L.) dominant pasture to validate the N dilution curve for temperate grass species. The extent of N deficiency of pastures which had suboptimal N was quantified by calculation of a ratio between measured N% of herbage and optimum N% from the N dilution curve. The N dilution curve had the form N% = 4.8 DM?0.35 (R2 = 0.65) and the NNI ranged from a maximum of 1.2, which indicated luxury uptake, to a minimum of 0.2, which has been proposed as the minimum NNI required to result in net growth. When moisture was adequate for growth, the main cause of yield differences between +N and ?N pastures was radiation use efficiency with ?N pastures producing 0.54 g DM/MJ PAR in spring or less than half that of +N pastures (1.16 g DM/MJ PAR). The intrinsic link between water availability and N uptake in dryland and irrigated pastures was explained (R2 = 0.88) by the relationship between the water use efficiency and N uptake ratio. Periods of low N uptake (N deficiency) were associated with low water use efficiency. |
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