Analysing the Benefits of Growing Crops after Rice in the Rice Growing Areas in Australia

摘要

The Murrumbidgee Irrigation Area (MIA), the Coleambally Irrigation Area (CIA), and theudMurray Valley (MV) constitute the major Australian rice growing areas and are located inudsouthern east Australia. According to the Ricegrowers' Association of Australia Inc. (2002),udthe annual value of production of rice was $357 million in 2001 and the industry generatesudmore than $500 million from value-added exports annually, allowing these rice growing areasudto play a significant role in the Australian economy.udThe rice growing areas are also among the areas where the sustainability of irrigatedudagriculture is under threat from rising watertables, soil salinity and other environmentaludconsequences. The depth to watertables in more than 70 per cent of the MIA (MIAudL&WMP, 1998), around 35 per cent of the CIA (CICL, 2001), and around 60 per cent of theudMV (Murray Irrigation, 2001) is now around two metres from the soil surface. With theudcurrent land use practices, around 20 to 30 per cent of regions such as the MIA couldudbecome moderately salinised in the next 30 years due to rising watertables (Humphreys et al.,ud2001). Water leaching and run-off from rice-based farms form further problems.udPaddocks are flood-irrigated during rice growing period between November to March.udAlthough irrigation water is released prior to rice harvest, much of the water is retained byudthe soil even after rice harvest. The soil then slowly drains this water along with the addedudwinter rainwater into the watertable beyond the root zone. This wet soil profile has theudpotential to become an extra economic resource for rice-based farms whenever it can be usedudto grow another crop during winter straight after rice.udGrowing winter crops immediately after rice harvest may reduce the amount of wateruddrainage into watertables on rice-based farms. Successful adoption of this potentiallyudattractive option seems to depend on good weather and rootzone water conditions, gooduddrainage and timeliness in the rice harvesting, stubble burning, and winter crop sowingudoperations. Among the constraints for adding crops after rice are too much rain orudwaterlogging for the winter crop to survive, problems with stubble burn, pests, weeds, andudunsuitable machinery leading to a high risk of crop failure (Humphreys and Bhuiyan, 2001).udAs one of the strategies to overcome the problems of rising watertables in rice growing areas,udthe Rice CRC is conducting Project 1205 “Quantifying and Maximising the Benefits of Cropsudafter Rice”, henceforward referred to as Project 1205. Project 1205 aims at determining theudconstraints and the success factors for rice growers to produce winter crops and pasturesudafter rice, and at measuring the impacts of this practice on environmental and economicudsustainability. In particular, the project aims to measure the effects of growing wheat afterudrice on the productivity and water use efficiency of the rice-wheat cropping system.ud2udThe objectives of this economic analysis of project 1205 are:ud· To identify the common crop rotations in the main Australian rice-based farming systems,udboth with and without crops after rice;ud· To estimate the potential financial benefits of growing crops after rice;ud· To identify the economic benefits to the community from reduced accessions toudgroundwater; andud· To compare returns with the costs to the CRC and its partners of developing andudextending this technology.udTo measure the likely financial and economic benefits of growing crops after rice, the studyudrelied heavily on the results from Humphreys et al. (2001).