WITH large tracts of south-eastern Australia experiencing record spring rainfall the issue of waterlogging is becoming a major problem.
Already, the NSW Department of Primary Industries has estimated there will be over $500 million worth of crop losses due to excess moisture in that state alone.
But the director of a precision agriculture (PA) business believes a few simple steps using PA principles can markedly lower the risk of waterlogging damage.
Andrew Whitlock, founder of Precision Agriculture, has been running a series of workshops through high rainfall zones in southern NSW and Victoria demonstrating how he has managed to mitigate problems with excess moisture through the use of simple PA techniques.
“The results are there. On a paddock I share-farm (in Victoria’s Western District) we have increased yield potential by 30 per cent by lowering the risk of waterlogging,” he said.
The good news for growers is that it does not require an intricate PA based farming system to achieve results.
“You can get the information you need to make changes from fairly simple data sets which most growers would have access to,” Mr Whitlock said.
He said the improvements came down to two major factors, the variable rate use of soil ameliorants such as gypsum and lime and the use of surface drains within the paddock.
“A lot of the issues from waterlogging come about on heavy, sodic and acidic soil so the use of gypsum and lime can really help.”
“It is also critical to ensure the crop does not sit in water for a prolonged period of time and surface drains help get the water off quicker.”
He said decisions on where to place the surface drains were made using elevation maps to ensure they are in the most efficient places while the gypsum and lime decisions are made by using yield and pH mapping.
“All of these types of maps are easily generated by the equipment used by the average farmer, you don’t need hundreds of different data sets to make your decisions.”
Variable rate gypsum applications help improve water infiltration in the soil and stop pooling which causes crop damage.
The amount of gypsum is calculated according to yield map and NDVI data, with sodic areas mapped and targeted.
“We use up to four tonnes to the hectare of gypsum on areas that need it, which a heavy rate, but that can be cut in lighter parts of the paddock where the sodicity is not so big a problem.”
“Overall we can still cut fertiliser costs by up to 30pc and still have a very heavy rate on the areas that need it.”
In terms of the drains, he said they cost around $30/ha, or around the cost of a selective herbicide application, to design and build, taking the water off the paddock and into local creek systems.
“That is a good thing for us that we can drain the water into a natural watercourse.”
“We have seen a marked drop in waterlogging from one year to the next.”
He said in the area he farmed, soil acidity was also a major yield constraint.
The use of pH mapping meant a variable rate liming program has been able to aggressively target the areas needing neutralizing in a similar manner to the gypsum application.
“Like the gypsum, we are able to put out fairly aggressive rates of 1500 to 2000 kilograms a hectare and still make savings on our fertiliser bills.”
In the longer term he said a diverse crop rotation, including legumes along with controlled traffic cropping could help improve soil health and permeability.
Earlier sowing has also helped keep water from causing crop damage.
“That has really worked for us in terms of getting a decent root system up and going before it gets really wet.”
He said a poor canola crop in 2013, where over 20pc of a paddock had 100pc crop loss due to waterlogging was the catalyst to finding solutions to waterlogging.
“Waterlogging had impacted 24 percent of a paddock, reducing gross income by $10,000.”
“We combined elevation data from our seeding application map with NDVI imagery maps to design a network of strategic spoon drains which cost us less than $3,000 to design and construct.”
“The key point is it can be done, and it can be done simply using good objective measures to help you make your decisions.”