Effect of irrigation scheduling on nitrous oxide emissions in intensively managed pastures

Denitrification is a key pathway of N loss in pastures and contributes to the low nitrogen use efficiency of these agroecosystems. Previous studies have shown irrigation to significantly increase nitrous oxide losses from fertilised agroecosystems. This study aimed to determine the effect of three irrigation frequencies on N2O emissions while maintaining pasture yield. High-resolution N2O data and biomass yields from each grazing were used to evaluate the mitigation potential of irrigation scheduling. Irrigation volumes were based on average monthly evapotranspiration and were applied at 4, 10 and 15 day intervals (High-Frequency, Medium-Frequency and Low-Frequency), with the aim of equal cumulative irrigation accounting for rainfall. Highest cumulative losses of 5855 ± 537 g N ha-1 were measured from the Low-Frequency treatment, which was significantly higher than the Medium and High-Frequency treatments with 3282 ± 190 g ha-1 and 3790 ± 448 g ha-1,respectively. Emission factors ranged between 0.49% and 1.17% for Medium-Frequency and Low-Frequency treatments respectively. Despite significant differences in losses, much of this variance was not directly related to individual irrigation events but to a treatment legacy seen during succeeding high rainfall events. These high losses from the Low-Frequency treatment have been attributed to the Birch Effect due to the severe drying of the soil profile between irrigation events; suggesting a future focus of research on wetting and drying cycles rather than absolute soil moisture contents.

[1]  Y. Benjamini,et al.  Controlling the false discovery rate: a practical and powerful approach to multiple testing , 1995 .

[2]  B. Ferrari,et al.  Legacy effects of soil moisture on microbial community structure and N2O emissions , 2016 .

[3]  J. W. Doran,et al.  Managing soil denitrification , 2002 .

[4]  K. Paustian,et al.  Influence of dry–wet cycles on the interrelationship between aggregate, particulate organic matter, and microbial community dynamics , 2001 .

[5]  C. Scheer,et al.  Impact of nitrification inhibitor (DMPP) on soil nitrous oxide emissions from an intensive broccoli production system in sub-tropical Australia , 2014 .

[6]  A. Ravishankara,et al.  Nitrous Oxide (N2O): The Dominant Ozone-Depleting Substance Emitted in the 21st Century , 2009, Science.

[7]  J. Minx,et al.  Climate Change 2014 : Synthesis Report , 2014 .

[8]  L. Zwieten,et al.  Effect of biochar amendment on the soil-atmosphere exchange of greenhouse gases from an intensive subtropical pasture in northern New South Wales, Australia , 2011, Plant and Soil.

[9]  R. Phillips,et al.  Nitrous Oxide Fluxes, Soil Oxygen, and Denitrification Potential of Urine- and Non-Urine-Treated Soil under Different Irrigation Frequencies. , 2016, Journal of environmental quality.

[10]  K. Weier.  Nitrogen use and losses in agriculture in subtropical Australia , 2004, Fertilizer research.

[11]  P. Bottner.  Response of microbial biomass to alternate moist and dry conditions in a soil incubated with 14C- and 15N-labelled plant material , 1985 .

[12]  H. Birch.  The effect of soil drying on humus decomposition and nitrogen availability , 1958, Plant and Soil.

[13]  Jiafa Luo,et al.  Nitrogen loss through denitrification in a soil under pasture in New Zealand. , 2000 .

[14]  G. Box,et al.  Distribution of Residual Autocorrelations in Autoregressive-Integrated Moving Average Time Series Models , 1970 .

[15]  N. Fierer,et al.  Effects of drying–rewetting frequency on soil carbon and nitrogen transformations , 2002 .

[16]  P. Doskey,et al.  Simulated rainfall on agricultural soil reveals enzymatic regulation of short-term nitrous oxide profiles in soil gas and emissions from the surface , 2016, Biogeochemistry.

[17]  Reiner Wassmann,et al.  Nitrous oxide emissions from fertilized, irrigated cotton (Gossypium hirsutum L.) in the Aral Sea Basin, Uzbekistan: Influence of nitrogen applications and irrigation practices , 2008 .

[18]  C. Scheer,et al.  Nitrous oxide emissions from irrigated wheat in Australia: impact of irrigation management , 2012, Plant and Soil.

[19]  Roland Bobbink,et al.  Nitrous oxide emission and denitrification in chronically nitrate-loaded riparian buffer zones. , 2003, Journal of environmental quality.

[20]  H A Deluyker,et al.  Replacement of missing values in time series data by Kalman smoothed estimators using state-space modeling. , 1988, Acta veterinaria Scandinavica. Supplementum.

[21]  J. Powell,et al.  Nitrogen use efficiency and manure management practices in contrasting dairy production systems , 2012 .

[22]  S. Ledgard,et al.  Nitrogen inputs and losses from clover/grass pastures grazed by dairy cows, as affected by nitrogen fertilizer application , 1999, The Journal of Agricultural Science.

[23]  Dj Donaghy,et al.  Plant-soluble carbohydrate reserves and senescence - key criteria for developing an effective grazing management system for ryegrass-based pastures: a review , 2001 .

[24]  C. Klein,et al.  Denitrification in the top soil of managed grasslands in The Netherlands in relation to soil type and fertilizer level , 1994, Plant and Soil.

[25]  A. Franzluebbers,et al.  Flush of carbon dioxide following rewetting of dried soil relates to active organic pools. , 2000 .

[26]  J. M. Bremner.  Sources of nitrous oxide in soils , 2004, Nutrient Cycling in Agroecosystems.

[27]  Jean-Pascal van Ypersele de Strihou.  Climate Change 2014 - Synthesis Report , 2015 .

[28]  M. Bethune,et al.  Overview of the irrigated dairy industry in Australia , 2004 .

[29]  Keith A. Smith,et al.  Global agriculture and nitrous oxide emissions , 2012 .

[30]  Andreas Meyer-Aurich,et al.  Irrigation, soil organic carbon and N2O emissions. A review , 2013, Agronomy for Sustainable Development.

[31]  M. Caldwell,et al.  A large ephemeral release of nitrogen upon wetting of dry soil and corresponding root responses in the field , 1997, Plant and Soil.

[32]  C. Klein,et al.  Denitrification in grassland soils in the Netherlands in relation to irrigation, N-application rate, soil water content and soil temperature , 1996 .

[33]  Paul E. Gessler,et al.  Modeling Soil–Landscape and Ecosystem Properties Using Terrain Attributes , 2000 .

[34]  J. Fuhrer,et al.  Temporal variation in N2O and N2 fluxes from a permanent pasture in Switzerland in relation to management, soil water content and soil temperature , 1999 .

[35]  C. Scheer,et al.  The nitrification inhibitor DMPP (3,4-dimethylpyrazole phosphate) reduces N2 emissions from intensively managed pastures in subtropical Australia , 2017 .

[36]  D. Chapman,et al.  Gaseous nitrogen loss from temperate perennial grass and clover dairy pastures in south-eastern Australia , 2003 .

[37]  K. Dittert,et al.  N2O emission and the N2O/(N2O + N2) product ratio of denitrification as controlled by available carbon substrates and nitrate concentrations , 2012 .

[38]  R Core Team,et al.  R: A language and environment for statistical computing. , 2014 .

[39]  E. Cowling,et al.  The Nitrogen Cascade , 2003 .

[40]  C. Kroeze,et al.  Closing the global N2O budget: A retrospective analysis 1500–1994 , 1999 .

[41]  P. D. Ruiter,et al.  Microbial numbers and activity in dried and rewetted arable soil under integrated and conventional management , 1992 .

[42]  L. Cárdenas,et al.  Effect of antecedent soil moisture conditions on emissions and isotopologue distribution of N2O during denitrification , 2011 .

[43]  J. Baldock,et al.  Reducing nitrous oxide emissions and nitrogen leaching losses from irrigated arable cropping in Australia through optimized irrigation scheduling , 2015 .

[44]  Franco Miglietta,et al.  Drying and wetting of Mediterranean soils stimulates decomposition and carbon dioxide emission: the "Birch effect". , 2007, Tree physiology.

[45]  Arvin R. Mosier,et al.  Assessing and Mitigating N2O Emissions from Agricultural Soils , 1998 .

[46]  R. Isbell.  Australian Soil Classification , 1996 .

[47]  Rob J Hyndman,et al.  Automatic Time Series Forecasting: The forecast Package for R , 2008 .