Ground Cover Supplement : GC Supplement - Nutrient Management 2006
ProjEct uPdAtE 8 Ground covEr nutriEnt mAnAGEmEnt Exports that waste money ProjEct: mAnAGEmEnt of hiGh-rAinfAll croPPinG to imProvE wAtEr QuAlity And Productivity PhilomEnA GAnGAiyA And dAvid nAsh tHiS nMi ProjeCt is systematically investigating the processes responsible for nutrient exports from high- rainfall ‘on-the-flat’ cropping systems. nutrients leaking (exported) from high-rainfall crop- ping systems, especially nitrogen and phosphorus, are both an economic and an environmental issue for the grains industry. nutrient exports represent wasted money and con- tribute to the excessive and often explosive growth of aquatic plants, including blue-green algae, in receiving waters. the excessive growth of aquatic plants – and oxygen depletion that results from their death and decomposi- tion – can restrict the use of key water resources for fisheries and recreation, and as industrial and domestic water supplies. this costs money! like the dairy industry, the grains industry, in partnership with the Victorian Department of Primary industries (DPi), has adopted a proactive approach in addressing nutrient exports from farms. limited infor- mation available from another project funded by the GrDC and the Victorian Government, at Mt Pollock in southern Victoria, suggests that phosphorus and nitrogen exports from ‘on-the-flat’ cropping systems are environmentally and economically significant; most of the phosphorus exported from systems on poorly drained soil was in a reactive and probably dissolved form, and most nitrogen was in the form of nitrate. these results are worrying. they suggest that nutri- ent exports from cropping systems, especially on poor- ly drained soils which dominate many parts of the Australian high-rainfall zone, are probably big- ger, more potent and more costly than had been hoped. importantly, if the nutrients are exported in a dissolved form (<0.45 micron, about the size of a virus or smaller) our current best management practices, such as grassed filter strips, will do little to stop them moving off-site and contributing to catchment scale impacts. For nutrients to be a water quality issue, there needs to be a source of nutrients which gets mobilised into runoff and transported to a location where an impact such as an algal bloom can occur. this project is using such a source-mobilisation- transport-impact framework to investigate nutrient exports from ‘on-the-flat’ cropping systems. Preliminary investigations are focusing on fer- tiliser as a source of nutrients. initial laboratory- scale studies suggest that depth of fertiliser place- ment could be important in reducing losses. these studies are being extended to fertiliser management effects in different tillage and stubble management systems, including investigations on the importance of other sources such as soil and plant residual nutrients. For studies on nutrient transport at the paddock scale, two sites at Cressy and Hamilton in the south- west of Victoria have been equipped with automated runoff monitoring equipment, and these measurements should provide an indication of the significance of nutrient losses over areas larger than the plot scales used for many runoff monitoring studies. Catchment- scale impacts are also being investigated by monitoring stream water quality in cropping areas. these investigations will provide the scientific foun- dation for developing improved high-rainfall cropping systems that will be communicated, in conjunction with Southern Farming Systems and other grower networks, to the farming community. Dr Philomena Gangaiya is a research scientist and Dr David Nash Statewide Leader – Soil Chemistry, both with the Victorian DPI. grDC research Code DaV00059 For more information: philomena gangaiya or David nash, 03 5624 2222, Philomena.Gangaiya@dpi.vic. gov.au, firstname.lastname@example.org the runoff monitoring site at Cressy in south-western Victoria.
GC Supplement - Farm safety
GC Supplement - Precision Agriculture 2005