Rice growing guidelines for managing water usage
1. Water budgeting
Water budgeting is very important as there is a direct correlation between water use and profitability. It is recommended that you record and understand your historical rice crop water use levels for each specific paddock before making sowing decisions. Strategies can be implemented to reduce crop water use.
Your local irrigation corporation may determine the Maximum Rice Water Use Volume each season. In the event that your rice water use exceeds the Maximum Rice Water Use Volume, then it is strongly recommended that you contact either Rice Extension or your local agronomist to review the water usage and develop a plan to reduce water use for the purpose of growing rice.
2. Soil Suitability
Rice growers should grow rice on suitable rice approved soil types. Information on rice soil suitability and soil survey maps for your landholding may be obtained from your respective irrigation corporation. Alternatively, a whole farm plan indicating approved soil types may be available from the previous owner/s of your landholding.
In the event that you do not have access to soil survey maps for your landholding, you should seek the advice of an accredited soil survey contractor regarding the suitability of land for rice production before growing rice on that land. The advice of the accredited soil survey contractor should be subject to an electromagnetic survey (EM31) and/or soil sodicity assessments.
3. Irrigation Infrastructure and Drainage
Drainage connected to recycling and storage infrastructure is essential for maximising water use efficiency. Level fields, optimum field grade, design and installation of appropriate sized stops and pipes for bay size and shape should all be considered. Quick water on-off time is important in irrigation and drainage to prevent drainage below the root zone into the water table.
On farm leaky supply and drainage channels and channel stops will use more water. It may be necessary to relocate channels and drains, or carry out clay lining and regular maintenance to prevent excess water usage.
Hold all rice water treated with herbicides or pesticides on-farm for 28 days before releasing from your property or have the water tested by your irrigation corporation before release into drainage.
4. Water Table Impacts
In the event that water table rises are being experienced nearby your landholding, your local irrigation corporation may alert you. It is recommended that you contact either Rice Extension or your local agronomist to investigate your water usage and develop a plan to reduce seepage in your local area.accredited soil survey contractor should be subject to an electromagnetic survey (EM31) and/or soil sodicity assessments.
5. Crop agronomy
Reducing the time the rice crop is ponded will reduce crop water use by limiting evaporation and deep drainage below the crop root zone.
Changing sowing method can reduce water use. In research trials, drill sown rice crops used 1.5 ML/ha less than aerial sown crops and 3.5 ML/ha less if the permanent water was delayed until late December. Delaying permanent water results in approximately 40 days less ponded time than conventional drill sowing and 75 days less than aerial sowing.
Crop water use can also be reduced by sowing shorter season varieties later in the year. Crop duration can be reduced by 30 to 45 days with similar yields by planting these varieties in late November.
More information is available in the NSW DPI Rice Growing Guide, Rice Variety Guide, Delaying permanent water on drill sown rice Primefact and Management of drill sown rice Primefact here.
Rice Extension, March 2018