Ketema Zeleke

Response of canola (Brassica napus L.) and mustard (B. juncea L.) to different watering regimes

In arid and semiarid winter crop growing regions of southern Australia, low rainfall, high evaporation, and low soil moisture storage are the limiting factors for crop production. In this region canola ( Brassica napus L.) is principally grown in rotation with wheat and pasture species. Some field studies have indicated Indian mustard ( Brassica juncea L.) to be more drought tolerant than canola and therefore considered to be better adapted than canola to short season environments. A field experiment was conducted at Wagga Wagga in NSW to determine the effect of two soil moisture regimes on water use efficiency, harvest index, seed and oil quality of cv. Oasis of Indian mustard and cv. Skipton of canola. Significant year × stress and species × stress interaction effects were observed for grain yield, harvest index, seed weight, biomass water productivity, and grain water productivity. Irrigation during the post flowering period resulted in 50% and 200% increases in canola grain yield in the first year (year with higher in-crop water) and the second year (year with low in-crop water), respectively. For mustard, these values were 7% and 45%, respectively. Stressed mustard resulted in higher grain yield than stressed canola while irrigated canola performed better than irrigated mustard. High mustard biomass production resulted in lowering its harvest index. Generally, the biomass water productivity of mustard was higher than that of canola. Grain yield-based water productivity of stressed mustard was higher than that of stressed canola while irrigated canola had higher water productivity than irrigated mustard. When rainfall and actual evapotranspiration drop below some thresholds, mustard becomes a favourable crop. Generally, effects due to the water treatments (stressed v irrigated) were much larger than the differences due to species.

Oil content and fruit quality of nine olive (Olea europaea L.) varieties affected by irrigation and harvest times

Abstract A field experiment was conducted on nine olive varieties with the objective of determining the effect of regulated deficit irrigation on olive oil content and physical quality parameters of fruits. Three irrigation levels were applied as a percentage of crop evapotranspiration (ETc) during the pit-hardening period: rainfed, R (0% ETc); deficit, D (50% ETc); and irrigated, I (100% ETc). Rainfall and ETc during the pit-hardening period were 78 mm and 164 mm, respectively. Olives were sampled four times during the normal crop harvest period. Withholding irrigation during the pit-hardening period (R treatment) reduced the fruit size of three of the varieties, but had no effect on oil contents, while saving 35% irrigation water compared with the I treatment. The D treatment resulted in 17.5% water saving with minor effects on fruit size, timing of maturity and oil content. The olive cultivars responded differently to irrigation treatments in terms of most of the parameters considered. This necessitates cultivar-specific irrigation management.

Modelling streamflow response to climate change for the Kyeamba Creek catchment of south eastern Australia

This study predicts the probable impacts of climate change on the streamflow of Kyeamba Creek catchment of south eastern Australia. Three climate scenarios (B1, A1B and A2) and the average of four general circulation models (CNRM-CM3, CSIRO-MK3.5, ECHam5 and MIROC3.2) were used to simulate the streamflow for three future periods (2030, 2050 and 2090). Soil and Water Assessment Tool (SWAT) was calibrated for streamflow of both daily and monthly time steps. Nash-Sutcliffe Efficiencies (NSE) of 0.602 and 0.657 for calibration and validation, respectively, for monthly time step indicate good agreement between measured and simulated flow for the catchment. Comparing with the long time observed streamflow, simulated future annual average streamflow showed a variation ranging from +16% to –44%. Based on SWAT simulations of this study, Kyeamba Creek will likely experience small change in streamflow by the middle of the 21st century but big change by the end of this century.

Rainfall-Runoff Modelling for Sustainable Water Resources Management: SWAT Model Review in Australia

Water is considered as a vital resource for survival, development and ecological needs. In a world of increasing water demand, planning for a sustainable system satisfying the demands of present and future without degradation of the ecosystem is a major challenge. Being the driest inhabited continent, Australia is not without this challenge and uncertainty in future water availability in the scenario of climate change is creating more pressure. Hydrological models are a useful tool due to the capability of simulating the past and future scenarios of a water management system to assess the balance between human and environmental demands. The physically based semi-distributed hydrological model Soil and Water Assessment Tool (SWAT) is such a tool that is capable of simulating a wide range of hydrological processes with different management scenarios. Although the number of SWAT applications in Australia is limited compared to other regions of the world, there are some important and diverse applications, from simple water balance assessments to complex environmental policy and water market evaluation. The review of SWAT applications in Australia revealed that despite several limitations, the model has a promising scope to explain Australia’s hydrology in the context of the sustainability of water resources management.