Analysing the Benefits of Growing Crops after Rice in the Rice Growing Areas in Australia03 November 2005
The Murrumbidgee Irrigation Area (MIA), the Coleambally Irrigation Area (CIA), and the Murray Valley (MV) constitute the major Australian rice growing areas and are located in southern east Australia. According to the Ricegrowers' Association of Australia Inc. (2002), the annual value of production of rice was $357 million in 2001 and the industry generates more than $500 million from value-added exports annually, allowing these rice growing areas to play a significant role in the Australian economy. The rice growing areas are also among the areas where the sustainability of irrigated agriculture is under threat from rising watertables, soil salinity and other environmental consequences. The depth to watertables in more than 70 per cent of the MIA (MIA L&WMP, 1998), around 35 per cent of the CIA (CICL, 2001), and around 60 per cent of the MV (Murray Irrigation, 2001) is now around two metres from the soil surface. With the current land use practices, around 20 to 30 per cent of regions such as the MIA could become moderately salinised in the next 30 years due to rising watertables (Humphreys et al., 2001). Water leaching and run-off from rice-based farms form further problems. Paddocks are flood-irrigated during rice growing period between November to March. Although irrigation water is released prior to rice harvest, much of the water is retained by the soil even after rice harvest. The soil then slowly drains this water along with the added winter rainwater into the watertable beyond the root zone. This wet soil profile has the potential to become an extra economic resource for rice-based farms whenever it can be used to grow another crop during winter straight after rice. Growing winter crops immediately after rice harvest may reduce the amount of water drainage into watertables on rice-based farms. Successful adoption of this potentially attractive option seems to depend on good weather and rootzone water conditions, good drainage and timeliness in the rice harvesting, stubble burning, and winter crop sowing operations. Among the constraints for adding crops after rice are too much rain or waterlogging for the winter crop to survive, problems with stubble burn, pests, weeds, and unsuitable machinery leading to a high risk of crop failure (Humphreys and Bhuiyan, 2001). As one of the strategies to overcome the problems of rising watertables in rice growing areas, the Rice CRC is conducting Project 1205 “Quantifying and Maximising the Benefits of Crops after Rice”, henceforward referred to as Project 1205. Project 1205 aims at determining the constraints and the success factors for rice growers to produce winter crops and pastures after rice, and at measuring the impacts of this practice on environmental and economic sustainability. In particular, the project aims to measure the effects of growing wheat after rice on the productivity and water use efficiency of the rice-wheat cropping system. 2 The objectives of this economic analysis of project 1205 are: · To identify the common crop rotations in the main Australian rice-based farming systems, both with and without crops after rice; · To estimate the potential financial benefits of growing crops after rice; · To identify the economic benefits to the community from reduced accessions to groundwater; and · To compare returns with the costs to the CRC and its partners of developing and extending this technology. To measure the likely financial and economic benefits of growing crops after rice, the study relied heavily on the results from Humphreys et al. (2001).