Unconventional path to applying water to rice
From the November 2008 edition of Agriculture Today.
Potential gross margins from water savings could more than offset yield losses, where rice farmers delay permanent applications of water.
Reduced water availability and drought have led a few rice growers to successfully trial the technique of delaying the application of permanent water, to save water and improve water productivity.
The thinking behind such a system is quite the opposite of conventional thinking on rice growing, according to NSW Department of Primary Industries (DPI) rice industry leader John Lacy and agronomist Rachael Whitworth.
"The application of permanent water is delayed until panicle initiation and flushes are only carried out to supplement rainfall to keep the crop alive," Mr Lacy said.
Rice is stressed more between flushes with this proposed system.
Due to the moisture stress the crop experiences, crop growth and yield are likely to be reduced by 10 to 20 per cent, compared to a conventionally grown crop.
"However with lower inputs and potential water savings of up to 20 to 30pc, the gross margin per megalitre of water applied and yield in tonnes per megalitre, are likely to be higher than a conventionally grown crop," Ms Whitworth said.
Last season Griffith grower, Dick Thompson, was able to achieve a water productivity of close to 1.2 tonnes per megalitre by delaying the application of permanent water.
He sowed the crop in early November and did not apply permanent water until mid December, at the time when the crop was severely moisture stressed.
It quickly recovered after the application of permanent water.
The crop was topdressed just prior to panicle initiation and Mr Thompson ensured that deep water was implemented at the critical early microspore stage.
This season a collaborative approach between NSW DPI and Murrumbidgee Irrigation will see two demonstrations carried out in the MIA with water stressed rice, where water use, rainfall, inputs and yield will be accurately measured.
Contact your local district agronomist if you are interested in trialling the delayed watering system.
