Effects of grassland management on plant nitrogen use efficiency (NUE): Evidence from a long-term experiment |
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| Affiliation: | 1. Ulster University, Cromore Road, Coleraine, Co. Londonderry, BT52 1SA, Northern Ireland, UK;2. Department of Biological Sciences, Imperial College, Silwood Park, Ascot, Berkshire, SL5 7PY, England, UK;3. Agri-Food and Biosciences Institute, 18A Newforge Lane, Co. Antrim, Belfast, BT9 5PX, Northern Ireland, UK;1. Naiman Desertification Research Station, Cold and Arid Regions Environmental and Engineering Research Institute, Chinese Academy of Sciences, Lanzhou 730000, China;2. Laboratory of Stress Ecophysiology and Biotechnology (LSEB), CAREERI, CAS, Lanzhou 730000, China;1. Institute of Plant Production and Protection, Universidad Austral de Chile, Valdivia, Chile;2. Instituto de Investigaciones Agropecuarias INIA, Remehue, P.O. Box 24-0, Osorno, Chile;1. Department of Biology, Utah State University, Logan, Utah 84321, USA;2. Department of Applied Economics, Utah State University, Logan, Utah 84321, USA |
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| Abstract: | Grassland management intensification can greatly influence nitrogen (N) dynamics between aboveground and belowground compartments mainly because of the large amount of available N forms, which are repeatedly added to soils. A better understanding of how chronic fertilisation might affect N use efficiency (NUE) in plants can contribute to reducing N losses from soils and improve the sustainability of managed grasslands. Here we address how NUE might be affected by (1) the addition of key nutrients (e.g. N, P, K, Mg) in different combinations, (2) grazing by rabbits, and (3) liming (i.e. CaCO3 applications) in a 22-year-old permanent grassland experiment established in Berkshire, UK, in 1991. We first calculate seven different NUE indexes, which are known to respond either to changes in soil N availability (i.e. endogenous N inputs from soil N mineralization processes) or to exogenous N inputs (i.e. synthetic N fertiliser). We found that plant NUE calculated as plant biomass produced per unit of N acquired significantly decreased under the chronic addition of multiple nutrients (NPKMg) and was even lower under N-only applications. Most NUE indexes significantly decreased under grazing but greatly increased under liming applications. We found evidence that NUE indexes, which accounted for endogenous N sources decreased at increased rates of soil N mineralization. Finally, we found no significant relationships between any of the NUE indexes and estimates of soil N losses (Mg N ha−1) or N retention in soils (i.e. units of soil N retained per unit of N added) calculated from changes in net soil N budget over 22 years. Our study carried out on relatively acidic sandy soils suggests how liming applications in combination with low levels of multi-nutrient additions (NPKMg) can significantly improve plant biomass production per unit of N added thus contributing to enhance the sustainability of managed grassland ecosystems. |
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| Keywords: | Grassland intensification Grazing Liming Nutrient fertilisation Plant yields |
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