Ground Cover Supplement : GC Supplement - Water use efficiency
0.5 – 0.75 0.75 – 1.0 1.0 – 1.25 1.25 – 1.50 1.50 – 1.75 0 250 500 1000 km Ground covEr WAtEr usE EfficiEncy 6 pressure deficit is smaller at 20̊C than at 30̊C. The shape of the curve demonstrates that changes in temperature have a greater impact on vapour pressure deficit than changes in relative humidity. We know that biomass production per mm water use is higher in winter than spring, and it is also higher in environments with low vapour pressure deficit. We also know that grain yield is determined in a critical window around flowering. To date, the vapour pressure deficit around flowering for wheat-producing shires has been mapped and substantial differences have been found. Typically, vapour pressure deficit increases northwards and inland (Figure 2). long term (1975 to 2000) mean yield was found to be lower in shires that have high vapour pressure deficit, which was expected. This knowledge is being used to adjust the 22kg grain/ha/mm benchmark for individual wheat- producing locations of Australia. Preliminary studies indicated the benchmark holds for south-eastern locations, where it was first calculated, but drops northwards. For example, for crops growing with a good supply of water and nitrogen, our calculations are 19kg/ha/mm at Goondiwindi, 18kg/ha/mm at Dalby, 16kg/ha/mm at Roma and 15kg/ha/mm at emerald. This drop is driven by climate factors, of which vapour pressure deficit is the most important. □ This article is based on research by Alastair Doherty, Victor Sadras, Daniel Rodriguez and Andries Potgieter. Grdc research code dAs00089 more information: Associate Professor victor sadras, principal crop physiologist, South Australian Research and Development Institute, 08 8303 9661, firstname.lastname@example.org tHe national water use effiCienCy initiatiVe an overarching initiative is working with farming systems projects across the country on increasing water use efficiency By James Hunt AS PART OF the GRDC’s national Water Use efficiency Initiative, 17 regional projects are located across the GRDC’s southern and western regions (see back cover). each regional project has identified the farming practices most likely to improve water use efficiency (WUe) in their region. management interventions identified by individual projects for experimental investigation and validation are listed in Table 1. These are based on GRDC project specification documents and on discussions held by CSIRO project members with regional project officers. The CSIRO project team has classified these interventions into management areas and identified four areas for concentration of science and modelling effort, which are common to many regional projects. These are: Grdc research code csP000111 more information: dr James hunt, research scientist, CSIRO Plant Industry, 02 6246 5066, email@example.com BEnchmArkinG driEr Air incrEAsEs trAnsPirAtion. figure 2 Vapour pressure deficit for a period around flowering for wheat-producing shires of australia. lower yield has been recorded in shires with higher vapour pressure deficit. Break crops includes experiments assessing the risk profile of break crops, and subsequent impact on wheat WuE. modelling will focus on development of credible break crop modules for existing production models (for example, APsim, Ausfarm), and long-term analysis of risk, rotation gross margin and whole-farm cashflow. stubble management (including the role of stock in cropping systems) the majority of projects are assessing the impact of stubble and weeds on conservation of soil water and nutrients, but also includes those investigating physical impacts of stock on soil and hence hydrology. modelling will focus on water balances including weed water use, and stock/crop WuE trade-offs at the whole-farm level including impact on risk profile and cashflow. matching investment to potential includes projects which are attempting to better define water limited constraints to production in their environments, and how management can be adjusted according to potential in order to maximise profitability. often these aim to parameterise, validate and demonstrate tools for forecasting yield potential, for example, yield Prophet®, APsim and various WuE-based techniques. division and distribution of crop water use (canopy management) Experiments that focus on crop management techniques that alter canopy and root development, and hence ratio of water transpired relative to evaporation, and the time at which water is used (pre/ post anthesis). modelling is likely to focus on improving current simulation of soil and plant physiological processes.
GC Supplement - Wheat breeding
GC Supplement - Agronomy