Abstract
The land disposal of waste and wastewater is a major source of N2O emission. This is due to the presence of high concentrations of nitrogen (N) and carbon in the waste. Abattoir wastewater contains 186 mg/L of N and 30.4 mg/L of P. The equivalent of 3 kg of abattoir wastewater-irrigated soil was sieved and taken in a 4-L plastic container. Abattoir wastewater was used for irrigating the plants at the rates of 50 and 100 % field capacity (FC). Four crop species were used with no crop serving as a control. Nitrous oxide emission was monitored using a closed chamber technique. The chamber was placed inside the plastic container, and N2O emission was measured for 7 days after the planting. A syringe and pre-evacuated vial were used for collecting the gas samples; a fresh and clean syringe was used each time to avoid cross-contamination. The collected gas samples were injected into a gas chromatography device immediately after each sampling to analyse the concentration of N2O from different treatments. The overall N2O emission was compared for all the crops under two different abattoir wastewater treatment rates (50 and 100 % FC). Under 100 % FC (wastewater irrigation), among the four species grown in the abattoir wastewater-irrigated soil, Medicago sativa (23 mg/pot), Sinapis alba (21 mg/pot), Zea mays (20 mg/pot) and Helianthus annuus (20 mg/pot) showed higher N2O emission compared to the 50 % treatments—M. sativa (17 mg/pot), S. alba (17 mg/pot), Z. mays (18 mg/pot) and H. annuus (18 mg/pot). Similarly, pots with plants have shown 15 % less emission than the pots without plants. Similar trends of N2O emission flux were observed between the irrigation period (4-week period) for 50 % FC and 100 % FC. Under the 100 % FC loading rate treatments, the highest N2O emission was in the following order: week 1 > week 4 > week 3 > week 2. On the other hand, under the 50 % FC loading rate treatments, the highest N2O emission was recorded in the first few weeks and in the following order: week 1 > week 2 > week 3 > week > 4. Since N2O is a greenhouse gas with high global warming potential, its emission from wastewater irrigation is likely to impact global climate change. Therefore, it is important to examine the effects of abattoir wastewater irrigation on soil for N2O emission potential.
Highlights
The emission of greenhouse gases (GHGs) increases with the rising global population (Preston et al 2006)
The following reasons could be attributed to the high nitrous oxide emission from the wastewater-irrigated soils: (i) the rate of nutrient loading through abattoir wastewater irrigation/high soil fertility, (ii) the process of denitrification and (iii) the anaerobic condition created by the excessive addition of abattoir wastewater
The mitigation options to reduce N loss include the use of nitrogenous inhibitors (NI), growing bioenergy crops and adopting efficient farm budgeting
Summary
The emission of greenhouse gases (GHGs) increases with the rising global population (Preston et al 2006). Human activities such as agriculture (e.g. chemical fertilisers), energy production (e.g. coal combustion), transport (e.g. fossil fuels) and other industrial activities are directly or indirectly contributing to the GHG emissions (Crutzen et al 2008). Among the various sources that are responsible for GHG emissions, energy production is the major contributor followed by land use change for agriculture and industrial activities (Meinshausen et al 2009; Cerri et al 2009). The global warming potential (GWP) varies between these GHGs, for example, N2O is 282 times more powerful than CO2 (Ravishankara et al 2009). Almost 80 % of N2O is emitted from Australian agricultural lands, originating from N fertilisers (32 %), soil disturbance (38 %) and animal waste (30 %) (Dalal et al 2003)
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