Fact Sheet VITICULTURE

WINEMAKING management in viticulture /201337496692?

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Background What is nitrification?

Nitrous oxide (N2O) is a potent greenhouse Nitrification is the aerobic process by which + - gas with a 100-year global warming potential (NH4 ) is oxidised to nitrite (NO2 ) - 298 times that of carbon dioxide (Victor et al. then further oxidised to (NO3 ). The 2014). N2O is a major radiative forcing gas, rate of nitrification in soil is strongly that is, it significantly retards the insolation influenced by temperature and moisture, and energy absorbed by the Earth from being increases by a factor of 3.6 for each 10 C radiated back to space (Myhre et al. 2015). It is increase between 5 and 25 C (Chen et al. also responsible for significant stratospheric 2010). is the anaerobic process - -depletion (Portmann et al. 2012). by which NO3 is reduced to N2O and gas (N2). Denitrification rates are influenced The major source of N2O from soils is from by many factors including soil pH, degree of the natural microbial processes of nitrification - anaerobicity of soil, soil carbon content, NO3 and denitrification (Bremner 1997). content and water content (Dalal 1998) Agricultural N2O emissions are primarily a (Figure 1). result of the addition of synthetic nitrogen (N) fertilisers and animal manure to soil. Nitrifying and denitrifying in the soil convert nitrogen into different forms depending on the soil environment.

Updated November 2015 Fact Sheet VITICULTURE

WINEMAKING /201337496692? pt=LH_DefaultDo main_15&var=&h ash=item2ee0a6 6474

Figure 1. The in vineyards. Nitrous oxide is produced by the conversion of nitrogen in the soil.

Management practices to mitigate N2O Soil cultivation emissions The reduction of tillage intensity is often cited The application of nitrogen to the vineyard as a preferable soil management system because of the benefits of reduced fuel Organic amendments (e.g. manures, emissions, increased soil carbon and composts and mulches) are often applied to consequent water holding capacity and the agricultural soils to supplement the soil with offset in atmospheric CO2. However, the effect nitrogen. All inputs of N, whether from of tillage on N2O emissions in vineyards is organic sources or synthetic fertilisers, inconclusive (Suddick et al. 2011). In theory, contribute to N2O emissions (Suddick et al. tillage increases N2O due to accumulation of 2011). The magnitude of the N2O emissions is – NO3 and higher rates of denitrification dependent on soil nitrogen and carbon (Suddick et al. 2011). Steenwerth and Belina content, soil moisture, pH and temperature. (2010) measured higher N2O emissions from a bare, herbicide-treated vine row compared to It is critical to apply nitrogen at the correct a cultivated vine row. The higher emissions time to maximise uptake efficiency and to measured from the herbicide-treated vine prevent N2O loss. Nitrogen fertiliser should row were thought to have occurred because only be applied to vineyards during periods of there were more weeds growing in the active root growth. In a Mediterranean cultivated treatment which extracted any climate, this occurs just before flowering and available nitrogen from the soil and thus post-harvest. The application of nitrogen at depleted the nitrogen available to the soil other times during the season will result in microbes. It was also thought that the greater nitrogen leaching and loss and may also lead presence of weeds in the cultivated soils to higher N2O emissions. might provide labile soil carbon substrates that could facilitate greater conversion of N2O

Updated November 2015 Fact Sheet VITICULTURE

WINEMAKING to N2 (Suddick et al. 2011). Garland et al. Acknowledgement (2011) also found no significant difference in This work was supported by funding from the N2O emissions from a no-till system and a conventional tillage system in a vineyard. Australian/201337496692? Government. Irrigation Referencept=LH_DefaultDos and further reading Water and nitrogen are two significant limiting Garland, G.M., Suddick, E., Burger, M., factors to wine-grape production that are Horwath, W.R., Six, J. 2011. Direct N2O emissions following transition from intrinsically linked to N2O production. main_15&var=&h Irrigation and nitrogen stimulate plant growth, conventional till to no-till in a cover cropped which may also enhance C storage in soils. Mediterranean vineyard (Vitis vinifera). Agric. Irrigation can also accelerate microbial Ecosystemsash=item2ee0a6 Environ. 144 (1-2): 423–428. turnover of C and N, which increases the Steenwerth, K.L., Belina, K.M. 2010. Vineyard potential for N O production (Suddick et al. 2 weed management practices influence nitrate 2011). However, irrigation can also prevent leaching and nitrous oxide emissions.6474 Agric. losses of N to the environment; for example Ecosystems Environ. 138 (1-2): 127–131. when incorporated using fertigation, volatilisation can be minimised. Suddick, E.C., Steenwerth, K., Garland, G.M., Smart, D.R., Six, J. 2011. Discerning A range of irrigation techniques have been agricultural management effects on nitrous trialled for their effect on N O and CO 2 2 oxide emissions from convention and emissions and have demonstrated the alternative cropping systems: a California case capacity to reduce N O emissions both 2 study. Guo, L., Gunasekara, A.S. and cumulatively and also temporally. In almonds, McConnell, L.L. (eds.) Understanding sub-surface drip irrigation (SSD) has greenhouse gas emissions from agricultural significantly reduced N O emissions (by 50%) 2 management. Washington, DC: American compared to furrow irrigation. N O emissions 2 Chemical Society: 203–226. from SSD were also significantly lower than surface drip irrigation when measured in the tree row for four days after fertiliser Contact application. Surface drip and microsprinkler irrigation led to slightly higher N2O fluxes due For further information, please contact: to the higher volume of irrigation delivered to AWRI helpdesk the soil. The decrease in N2O measured under a SSD irrigation system is a result of restricted Phone 08 8313 6600 Fax 08 8313 6601 microbial activity and anaerobic microsite development, which limits denitrification Email [email protected] (Suddick et al. 2011). The use of SSD has other advantages including the reduction of Website http://www.awri.com.au/ evaporative losses from the soil surface; Address Wine Innovation Central Building, however it is not widely adopted in viticulture Corner of Hartley Grove & Paratoo Rd, due to the increased difficulty of maintenance Urrbrae (Adelaide), SA 5064 compared to above ground drip systems.

Updated November 2015