Inter-seasonal Nitrogen Loss with Drought Depends on Fertilizer Management in a Seminatural Australian Grassland
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Inter-seasonal Nitrogen Loss with Drought Depends on Fertilizer Management in a Seminatural Australian Grassland Mohammad Rahmat Ullah,*
Paola E. Corneo, and Feike A. Dijkstra
Sydney Institute of Agriculture, The University of Sydney, 380 Werombi Road, Brownlow Hill, Sydney, New South Wales 2570, Australia
ABSTRACT Drought can increase nitrogen (N) loss due to enhanced asynchronicity between N release through mineralization and plant N uptake. Organic amendments of N could potentially mitigate this loss where the N is more slowly released and made available at times when plants need it. Drought (ambient vs. reduced precipitation implemented with rainout shelters) and fertilizer addition (compost vs. mineral fertilizer) were used to examine the changes in mineralization, plant uptake, and loss of N during dry and wet periods in a grassland of Australia. Both gross N mineralization (GNM) and plant N uptake were high in wet summers and low in dry summers, while in the winter the relatively high GNM was not matched
with similarly high plant N uptake. Drought conditions combined with mineral fertilizer addition resulted in the highest plant d15N values, reflecting a more open N cycle (high N loss). In contrast, under drought conditions, compost released N more slowly and showed greater synchronicity with plant N demand. Because drought has become increasingly more intense and frequent, compost addition to grasslands could be a beneficial management strategy to improve soil health and increase plant productivity, and most importantly to reduce N loss compared to mineral fertilizers. Key words: drought; fertilizer; grassland; mineralization; nitrogen loss; plant N uptake.
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Received 14 August 2019; accepted 23 November 2019
Electronic supplementary material: The online version of this article (https://doi.org/10.1007/s10021-019-00469-4) contains supplementary material, which is available to authorized users. Author Contributions: MRU and FAD conceived the ideas and designed the study. MRU collected and analyzed the data with help from PEC. MRU prepared the original draft, and FAD and PEC reviewed and edited the manuscript. *Corresponding author; e-mail: [email protected]
Drought effects on mineralization and plant uptake of N were not in synchrony. High plant d15N values under drought conditions reflected a more open N cycle. Compost addition can reduce N loss with drought compared to mineral fertilizers.
M. R. Ullah and others
INTRODUCTION Global warming has altered precipitation at global and regional scales causing more frequent and intense droughts in most parts of the world (Handmer and others 2012). Climate models predict that most of the regions of the world will become drier by 2100 (Huang and others 2016). Water limitations caused by drought directly and indirectly affect most microorganisms (Hartmann and others 2013) that are responsible for the mineralization of nitrogen (N) in soil (Homyak and others 2017). Drought also tends to reduce plant N uptake because of reduced plant
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