Farmers who have invested in 2 cm accuracy RTK Global Positioning System (GPS) auto-steer tractor guidance technology have the added bonus of being able to collect highly accurate elevation data to map cost-effective drainage lines and erosion control structures.

When this topography data is combined with satellite imagery, the resultant elevation maps clearly identify areas affected by water logging and the natural drainage points.

Using this topography data in conjunction with newly developed Precision Agriculture (PA) Optisurface technology, farmers can slash the cost of rectifying soil erosion and drainage problems and reduce the amount of soil being moved by up to 90 percent when compared with traditional means such as laser levelling.

Department of Employment, Economic Development and Innovation Agri-Science Queensland extension officer Max Quinlivan, Emerald and agricultural consultant Tim Neale, Precision Agriculture.com.au, Toowoomba, recently finalised a two-year Precision Agriculture investigative project funded by Fitzroy Basin Association.

The Central Highlands PA project involved cooperative field studies on two irrigation properties - Mike Brosnan’s Emerald Downs (Emerald) and Neek Morawitz’ Argoon (Comet) - and two dryland farms - the Storey family’s Moonggoo (Capella) and the Bates family’s Bendee (Gindie).

Mr Quinlivan said the study aimed to assess PA and remote sensing technologies that could complement existing management strategies and rank the PA tools with the most value to assist Central Queensland farmers with their decision-making and on-ground practices.

"It is estimated that the majority of Central Queensland’s 600,000 ha of cropping land has been affected by soil erosion that warrants remedial action," Mr Quinlivan said.

"Soil erosion incurred within one of our project paddocks cost up to $102/ha in lost yield based on four years of data from 2006 to 2009.

"The value of lost yield attributed to erosion from six project paddocks ranged from $18 to $102/ha and averaged $48/ha.

"Soil sampling confirmed that erosion caused a reduction in plant available water capacity and this exacerbated crop yield decline in dry years.

"When we looked back at historical aerial photography, erosion in the worst-affected paddock occurred some 30 years ago and it appears that yield losses had continued to occur for every crop grown."

Mr Quinlivan said the extrapolated 30-year yield loss could be in the order of $1500/ha. By quantifying these losses allows the grower to develop a business case for erosion control.

"We believe that this is the first time that the cost of soil erosion has been really quantified at paddock level," he said.

Prior to the advent of no tillage farming, Fitzroy Basin grain growers practising conventional farming were losing up to 25 tonnes of soil per hectare per year to sheet erosion from cultivation paddocks.

Zero till cropping in combination with Controlled Traffic Farming had reduced soil erosion losses to just a few tonnes per hectare annually and even in the severe summer flooding of 2008, soil erosion from some no till paddocks was just 5 t/ha.

Mr Quinlivan said that during the 2008 Emerald district flooding, soil erosion from zero till paddocks with 60 per cent cover provided by an actively growing sorghum crop was just 5 t/ha. When compared with similar major flood events in the 1980s, soil erosion losses reached 25 t/ha and higher.

"Where water drains to a localised point, it leads to rill erosion which is still a major production and environmental issue faced by the region’s farmers," he said.

Mr Quinlivan said that thanks to the data collected by the RTK GPS guidance technology, farmers have a unique opportunity to minimise soil erosion and manage surface water to prevent water logging.

"The next step is to test the software on sloping lands in Central Queensland to see if we can predict soil erosion hot spots and better plan remedial action," he said.

Originally posted by Graeme Cox, PhD of Precision Agriculture, BAE, Director of OptiSurface

http://optisurface.ning.com/profiles/blogs/optisurface-and-autosteer-gps, Novemeber 2010