A farmer workshop sponsored by NRM South and Macquarie Franklin (Water for Profit) on the principles of drainage was held at Jericho on Thursday 12 May and attracted an excellent turnout of farmers.
Understanding water drainage on farms is critical to productivity even in apparently dry landscapes is a key message delivered by soils expert Dr Bill Cotching and Greg Gibson a Hagley producer and Nuffield Scholar who studied farm drainage with visits to North America and Europe. Dr Cotching said that based on his experience in advising farmers on drainage systems over many years, farmers can achieve at least a 20% increase in pasture growth and utilisation if good drainage in installed. He also noted that the pay-back period is likely to be in the first year after installation.
The workshop covered the principles of drainage, including the causes of drainage, the impact of poor drainage on crops and the environment, and principles for managing drainage issues. Dr Cotching explained the four rules of farm drainage:
Rule No. 1 – Design your drainage in winter and install drains in summer. Design is winter is necessary to see water flows, ponding and saturated areas, but installation in summer is best to operate machinery on firmer ground.
Rule No. 2 – Check the outfall. This involves checking levels to ensure water will flow off your paddocks otherwise drainage can create flooding.
Rule No. 3 – Isolate low lying areas from up-slope water. This can be achieving through arterial drains that capture water from up-slope areas. Elevating top soil can be achieved through lowering the water table with a drain or mounding the top soil above the water table.
Rule No. 4 – Staged drainage development is recommended. The stages are: 1. dealing with the outfall to ensure water flows off the paddocks; 2. installing the main arterial drains to isolate low lying areas from up-slope water; 3. installing the paddock drains (trench or surface) to connect to the arterial drains; and 4. installing underground drains (agricultural pipe) if necessary to connect with paddock and arterial drains.
Greg Gibson discussed systems and technology he has adopted following his Nuffield Scholarship. His key message is that reducing water logging can significantly boost your bottom line. Greg described tools that he uses including soil testing, EM38 mapping, physically looking at the ground and the variability of a crop or pasture; mapping the Normalized Difference Vegetation Index (NDVI); yield mapping including adding associated cost and returns; and data stacking (layering soil, NDVI, yield and profit loss maps) to work out a production strategy based on drainage.
In the afternoon, the workshop 20 participants groundtruthed the morning’s presentations with field walks on the properties of Andrew McShane (Park Farm) and Damian Burbury (Bowsden Farm).
The workshop was delivered with the support of NRM South’s RLF- Ken Moore.