Safflower doubles as watertable pump
GroundCover™ Issue: 41
SAFFLOWER IS known as a minor winter oilseed crop but it may have an expanded role in southern Australian farming systems as a dryland salinity controller, thanks to its vigorous taproot and later maturity.
PhD research student Nick Wachsmann, together with David Jochinke and supervisors Sue Knights and Rob Norton, compared safflower's water use with four other winter crops - Linola, mustard, canola and wheat - in a project supported by growers and the Federal Government through the GRDC.
Working from the University of Melbourne's Joint Centre for Crop Innovation near Horsham during 2000 and 2001, they measured comparative growth, yield and water use across four sites in western Victoria. Soil moisture, rainfall and temperatures varied between the site at Minimay near the Victorian/SA border and Longerenong in the central Wimmera in 2000 and two other sites near Longerenong last year.
Although results varied across the sites, safflower demonstrated its potential valueas a 'soil drying' agent as well as producing a marketable oilseed product.
Sceptical farmers might say surplus soil moisture was the least of their problems during most recent seasons, but waterlogging caused by late season rains can carry both short~ and long~term penalties. In wetter seasons, excess soil moisture can raise watertable levels.
On-farm experiments set research direction
Mr Wachsmann, who was raised on a farm, used farmer survey analysis to determine research priorities. "A survey we did a while ago found that some farmers used safflower to dry out waterlogged paddocks and had better performing crops in the subsequent year, e.g. beans, due to reduced waterlogging." Also from that survey some farmers in drier situations reported that excess water use by safflower resulted in poor subsequent crops.
"Our trials showed safflower's extended growing season of some 34--40 days more than wheat enabled it to extract additional water using its vigorous taproot system. This de~watering action could have a role in a dryland salinity control program," he said.
On the wetter sites, safflower reached physiological maturity more than a month later than wheat and subsequently used an additional 100 mm of water, Mr Wachsmann said.
Another consequence of these particular properties was that safflower could mine deeper subsoil moisture and possibly nutrients, beyond the reach of other winter crops.
Strategic control agent
In fact, safflower could act as a strategic natural watertable control agent sown in those parts of the farm where groundwater tables are suspected or known to be rising and encroaching into the cereal root zone. This might be in poorer soil profiles.
" Used in this way safflower could have a new role. We know, on the wellest sites in our trial, safflower yielded up to 3.71 lIha, similar to canola at 3.44 t/ha, but required an additional 120 mm of water to do so," Mr Wachsmann said.
Sowing safflower in waterlogging~prone areas could be an alternative to the expensive practice of raised~bed formations to provide a free~draining microenvironment for susceptible winter crops.
But on the downside, safflower's slower maturity characteristics sometimes worked against it as soil moisture reserves ran out late in the season and its seed yields plummeted. Limited markets for safflower arc a further disadvantage.
"At least for wet environments, the point is more a holistic thing, where even if safflower made less money in year 1, following crops did better in year 2. That's a good thing.
"Also, if safflower can help reduce salinity by reducing the amount of excess moisture reaching watertables, then there is a long~term benefit which is difficult to measure.
"I guess it's partly about using safflower as a tool, as well as increasing cropping options, e.g. a market buffer through enterprise diversity and increasing rotation and herbicide options," said Mr Wachsmann.
Contact: Mr Nick Wachsmann