Plant Soil 256:217–229Īsseng S, Keating BA, Huth NI, Eastham J (1997) Simulation of perched watertables in a duplex soil. Aust J Agric Res 49:345–361Īsseng S, Van Herwaarden AF (2003) Analysis of the benefits to wheat yield from assimilates stored prior to grain filling in a range of environments. The findings will have significant implications for estimates of future climate change impacts in this region with changes in rainfall causing non-proportional impacts on production and hydrological aspects, such as deep drainage and waterlogging, where proportionality is often presumed.Īnderson GC, Fillery IRP, Dunin FX, Dolling PJ, Asseng S (1998) Nitrogen and water flows under pasture–wheat and lupin–wheat rotations in deep sands in Western Australia-2. These results were due to the rainfall changes mainly occurring in June and July, a period when rainfall often exceeds crop demand and large amounts of water are usually lost by deep drainage. At the same time, simulated drainage decreased by up to 95% which will significantly reduce the spread of dryland salinity. Despite the large decline in rainfall, simulated yields based on the actual weather data did not fall. We used the ASPIM-Nwheat model in combination with historic climate data to study the impact of recent climate change on the hydrology and production of wheat based farming systems by comparing results for before and after 1975. Across nine sites, growing season rainfall (May to October) decreased by an average of 11% and the sum of rainfall in June and July (June + July) decreased by 20%. Since the mid 1970s the region has experienced a significant decrease in winter rainfall. Due to clearing of native vegetation, dryland salinity is a major problem in south-west Australia. The main factor limiting plant production in this region is rainfall. The goal is to manage cultural practices and irrigation timing such that the resulting water stress has less of a negative impact on grain yie.The wheatbelt of Western Australia shows a distinct Mediterranean climate with most of the rainfall occurring in the winter months.
Performance of the apsim wheat model in western australia full#
Under limited irrigation, less water is applied than is required to meet full ET demand and the crop will be stressed. UNL research suggests that applying limited water to an optimum number of acres provides more profit potential and has less impact on the local economy than converting some land to dryland (Schneekloth et al., 2001). The economic reality is that irrigation provides more stability and income than dryland farming. In many areas it simply means less water for producers. The passage of Nebraska legislation to conjunctively manage groundwater and surface water has changed ground and surface water management. The drought across the High Plains and inter-mountain west from 1999 to 2008 magnified the seriousness of the problem, however. To reflect the trends of soil organic nitrogen, it was necessary to consider the historical management starting the model in 1910.īACKGROUND Declining ground water is not a new dilemma in Nebraska or throughout the Great Plains. Although simulated soil mineral nitrogen content was mostly within the standard deviation of the replicate measurements, the very high variability of the measurements resulted in small correlations between simulation and observations (r2=0.22***). Especially the performance of the crop yield estimation dropped down significantly without re-initialisation of water contents in spring. This was due, at least in part, to the model's inability to estimate surface runoff, which occurred during periods of snowmelt when the soil was still frozen. Soil water content during the growing season was simulated well with r2 of 0.80*** however, simulating soil water dynamics during the winter period was problematic. The model simulated crop biomass, grain yields and nitrogen uptake well, with coefficients of determination (r2) of 0.88***, 0.70*** and 0.71***, respectively. Model performance was analysed by comparing the simulated state variables in soil and crops to measured data. Results of two rotations (continuous wheat and fallow–wheat) were compared in terms of crop biomass and grain yield production, water and nitrogen dynamics and nitrogen losses by leaching and denitrification. Selected treatments of a long-term field experiment, established in 1967 at Swift Current in southwestern Saskatchewan, Canada with different crop rotations were simulated over a period of 25 years using the integrated soil–crop model HERMES. Water and nutrient dynamics of soils are strongly related to land use and crop biomass production.
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