Elsevier

Agricultural Systems

Volume 158, November 2017, Pages 61-67
Agricultural Systems

An irrigated cotton farm emissions case study in NSW, Australia

https://doi.org/10.1016/j.agsy.2017.09.005Get rights and content

Highlights

  • Rotating cotton with legumes can achieve abatement with potential economic incentives depending on the commodity price.

  • EEFs will theoretically reduce emissions, however newer products are yet to be proven in cotton and vertosol soils.

  • Tree establishment for emission sequestration is high cost and risky in semi-arid areas where cotton in grown.

  • Using multiple strategies allows farmers to maximise abatement and gross margin from season to season.

Abstract

The primary source of emissions in broadacre cropping is synthetic fertiliser applied to farmland, creating nitrous oxide from chemical processes in the soil. In high yielding irrigated cotton production, nitrogen remains a key input to maintain yields and maximise crop returns. This study aims to identify immediate strategies available to broadacre irrigation to reduce emissions and maintain profitability. Four emission mitigation strategies on a large broadacre irrigation farm in Northern New South Wales producing cereals, pulse and cotton crops were modelled. The results show rotating cotton with pulse crops, instead of wheat, can achieve an 8% reduction in emissions and increase whole farm gross margin by 12%, due primarily to the current historically high chickpea price and a reduction in applied nitrogen. Combining enhanced efficiency fertilisers in cotton crops in a more comprehensive abatement strategy has shown an indicative 13% emissions reduction from the baseline scenario, with a 6% reduction in farm gross margin from the increased fertiliser cost. However, uncertainty regarding the impact of EEFs on cotton yield in vertosol soils is noted. The soil sequestration from including a tree-lot in the emissions reduction strategy reduced whole farm emissions by 11% and reduced whole farm gross margin of 3%; however, difficulty in establishment and high establishment costs can add economic risk. Combining all three emissions reduction strategies results in a significant emissions reduction of 33% and a 4% gain in whole farm gross margin. Sensitivity analysis highlights gross margins results to be particularly sensitive to chickpea price movement. With this desktop modelling in mind, the discussion draws on industry research revealing that at a field scale, carefully balanced agronomic nuances exist between cotton cropping rotations and secure economic outcomes. The addition of achieving environmental objectives simultaneously with these variables is yet another future challenge facing government emissions abatement incentive programs and broadacre cropping businesses.

Introduction

Identifying management strategies that deliver favourable environmental outcomes while maintaining profitable farming businesses is a challenge. Furthering this challenge is the instability in government carbon and energy policy initiatives aiming to reduce greenhouse gas (GHG) emissions.

Emissions in the agriculture sector include methane and nitrous oxide, which are generated by biological processes. The cropping sector in Australia contributes 2.5% to national GHG emissions and overall, agricultural emissions are expected to grow by 23% from 2012 to 123 M tonnes (Mt) CO2e by 2030 (Department of the Environment, 2013). The Australian Government reports on emissions across different industry sectors in the National Greenhouse Gas Inventory (NGGI) accounts (Australian Government, 2013). Currently, a key component of Australia's emissions reduction efforts is the Federal Government's Emissions Reduction Fund (ERF), a market-based mechanism designed to encourage lowest cost GHG abatement through participation in a reverse auction selling Australian Carbon Credit Units (ACCU) to government as sole purchaser. Although broadacre agriculture currently has little financial incentive and few available offset methods to enable participation in the ERF (Welsh et al., 2015), policy makers continue to encourage industry sectors within agriculture to work towards participation. In doing so, the agricultural sector can formally contribute to the national effort of meeting agreed reduction targets by 2030, as outlined in the COP21 Paris Agreement (UNFCCC, 2015).

Since the Carbon Farming Initiative Act was legislated in 2011 (ComLaw, 2011) a number of industry emission accounting tools have been developed to assist agricultural producers and farm advisors to understand the drivers of emissions by designing production scenarios within each industry model and recording changes from a baseline (Australian Carbon Traders, 2015). This paper aims to outline four emission reduction strategies appropriate for cotton production systems and considers changes in farm emissions and gross margin.

Section snippets

Methods

In this paper, cropping and emissions scenarios (cropping rotations, changes in fertiliser management, land-use changes) have been analysed for a case study farm using the FarmGas Calculator Scenario Tool (ST) developed by the Australian Farm Institute (Australian Farm Institute, 2016). Separate gross margin budget analysis was conducted indicating the change in farm gross margin and the marginal cost of abatement.

Results

The three year rotational cropping summary for the case study farm baseline scenario was summarised on an annual basis in Table 3. Table 4, Table 5, Table 6, Table 7 outline the cropping summary for each of the modelled emission reduction scenarios.

Table 8 summarises the GHG emissions and gross margin results of each scenario. Gross margin calculations consider the impact on variable costs of each land use change.

The economic analysis of each scenario provides a useful guide to risk assessment

Discussion/conclusion

This study has shown that trade-offs exists between GHG and profitability of an irrigated cotton farm in some abatement scenarios. Using the FarmGas ST, estimated on-farm emissions for a large broadacre cropping enterprise can be reduced by changing land use, cropping enterprises and fertiliser programs. A combination of these strategies, if successful, can lead to substantial reductions in whole-farm emissions and emissions intensity per cotton bale by as much as 33%, while maintaining farm

Acknowledgements

Bill Back from AusCott Ltd. generously provided valuable time and information from Togo Station operations to run the emissions and economic analysis.

This project has also been supported by the Australian Governments' extension and outreach grant EO12-01-0118 and the Cotton Research Development Corporation.

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