GPS offers new approach to paddock renovation
Heavy rain over three days provided a wet backdrop to the first International Controlled Traffic Farming Conference held at the Empire Theatre in Toowoomba, Queensland, in late March.
It was the beginning of three weeks of rain that caused more flooding across southern Queensland and northern New South Wales, and starkly emphasised the importance of soil conservation in controlled-traffic farming (CTF).
Toowoomba-based agronomist Tim Neale from Precision Agriculture said the flooding had displaced tens of thousands of tonnes of soil on grain growers’ properties, which costs about $2 per tonne to replace using conventional laser-levelling.
However, the conference heard that after taking a serious financial hit in the wake of the 2011 floods, many growers have been testing a comparatively low-cost GPS alternative to laser-levelling. The system was developed by Queensland growers David and Graeme Cox.
Mr Neale said the GPS approach enabled a more precise approach to paddock renovation by incorporating, rather than flattening, the land’s natural contours.
It means small peaks and troughs can be left alone, and the earthmoving kept to just the areas that needed to be cut or refilled. Mr Neale said many growers were finding this was reducing the work and cost by about 40 per cent. The approach uses the two-centimetre accuracy of a GPS unit mounted on a tractor or a quad bike to record surface elevation every few metres.
GPS units are able to covert this data into detailed topographical maps, which can be run through OptiSurface® software to design an appropriate surface gradient that involves shifting the minimum amount of soil.
In contrast with laser-levelling that cuts and fills the soil profile to create a completely flat surface, OptiSurface® GPS land-forming only cuts away soil where it is less than the desired minimum slope.
The cut soil is used to fill large hollows in the soil surface that interrupt the controlled flow of water from paddocks and which could cause waterlogging.
Mr Neale said that apart from reducing earth-moving costs, GPS-guided paddock renovation also resulted in less topsoil disturbance, lessening the exposure of fragile subsoils.
North Queensland grower David Cox said he developed the GPS-based system with his nephew Graeme to improve the efficiency of paddock renovation on his large-scale sugarcane farm.
Mr Cox said they had calculated that conventional laser-levelling was requiring them to move up to 400 per cent more soil than was actually needed on their property beside the Burdekin River, about 25 kilometres west of Ayr.
Mr Neale said another benefit that had emerged from the use of GPS was the ability to compare elevation data before and after flooding.
This provides an accurate measure of the amount of soil displaced by the flooding, which can help growers quantify the amount of soil they need to move and the costs involved.
However, he added that this was only possible if the same vehicle was used to collect elevation data and the base station had not been moved.
Mr Neale said topographical maps can also be overlaid with high-resolution aerial or satellite images to help growers better see areas prone to erosion and waterlogging.
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