Mortatha Ogee1, Chris Guppy1, Richard Flavel 1 , Graeme Blair1
1 Agronomy and Soil Science, University of New England, Armidale NSW, Australia. firstname.lastname@example.org
A glasshouse study was undertaken of the effect of phosphorus and water interactions on the productivity of intercropped sorghum and soybean grown in a Vertosol soil. Soybean or sorghum were grown alone or mixed. Difficulties in maintaining soil moisture near field capacity resulted in transient waterlogging in the sole soybean treatments which limited aeration in the root boxes. This resulted in reduced N2 fixation with the lowest shoot yields being in inoculated treatments. The shoot dry yield data showed that the growth of mixed soybean with N fertiliser gained a benefit when grown with sorghum, most likely due to a reduction in waterlogging stress as a result of the greater water use by the sorghum. Fertiliser P uptake was similarly affected. Sorghum was more competitive for P fertiliser than soybean when the fertiliser was applied between the plants, but the competition was marginal when the fertiliser was applied beneath each plant.