Variations in the performance of maize (Zea mayz) yield under reclaimed wastewater irrigation in south-eastern Australia : management of salinity, water and nutrient budgets
Abstract: This study explores the variations of maize growth performance under reclaimed wastewater irrigation and whether the dissimilarities in growth between and within the irrigation bays depend on dysfunctional salt, water or nutrient budgets. The experiment was conducted by Melbourne Water in conjunction with the Swedish University of Agricultural Studies at Melbourne Water's Western Treatment Plant in south-eastern Australia during the growing season of 2005/2006. Soil sampling from four irrigation bays found a generally lower electrical conductivity (EC) of the surface (0-10cm) than expected and those salt concentrations would not have had a severe impact on maize growth. However, some samples showed high salinity, still, the correlation with maize performance, measured as crop height (m), was very low (R2 0.02-0.44). Deep profile sampling could not be done in this study, hence, the salinity with depth was not explored. Information on current irrigation application (frequency and amounts) and water quality (salinity and nutrients) were collated from available data and processed. The current irrigation schedule was found to be too infrequent with too much water being applied at each of the irrigation events. The irrigation water salinity was rather low and would not have had a severe effect on crop growth in its own right and the nutrients applied through the irrigation water appeared to be within a, for the crop, proper range. In conclusion, possible high salt concentrations with depth may still be a problem for maize growth and should be investigated further and the irrigation application will have to change to a more frequent schedule with less amount of water applied at each irrigation event. The nutrients will have to be measured at the irrigation bays, not in the lagoons and pumping stations as it is done today, because the nutrient chemistry in the water may change along its way to the crop in such a way that the maize nutrient requirement is not met although believed so. Furthermore, one bay showed extremely high pH, which, together with low salinity is an indication of high sodicity, a factor that was only briefly explored in this study and should be researched extensively as it could have a severe impact on maize growth. Additionally, further studies on groundwater levels and drainage are required to make sure that a healthy environment for maize growth is created.
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