07 February 2018
WHEN WILL I START IRRIGATING AFTER RAIN?
Most irrigation systems in the Isis Mill Supply Area cannot apply enough water to meet crop water use during peak demand periods (Dec - Feb). To maximise cane growth and reduce the period the crop is stressed growers should startirrigating soon after rain.
Where rain has filled the profile, growers should start irrigating as soon as the soil water used by the crop is equal to the amount being applied. This will fill the soil profile in the absence of deep drainage and surface runoff.
The Isis Productivity Ltd and ICM websites provides access for growers to live soil moisture data from soil probes scattered around the mill supply district in varying soil types.These probes can provide growers with a visual guide to soil moisture levels and crop water use in those locations.
Of course, not all situations will be the same so utilise your own knowledge of individual blocks and soil types on your farm to assess the suitability of this irrigation strategy.
A push rod (build you own moisture push probe) can be an extremely handy tool to assess both compaction and soil moisture in the profile so don’t be afraid to get out and have a look.
The following is an example of the start up (post rainfall) irrigation strategy you can put in place.
Example: In February,70mm of steady rainfall over three days fills the soil profile.
Your cane is 2-2.5m high using approx 6mm of water/day.
Your irrigation system can apply 40mm of irrigation per pass.
7 days after rain the crop has used 42mm (7 days @ 6mm/day) where no other agronomic constraints are present.
∗ Starting the irrigation cycle now will fill the profile without runoff or deep drainage (dependent on soil type and irrigation method used).
∗ Start on driest and well-drained blocks - avoid waterlogged blocks.
∗ Applying this 42mm can prolong stalk growth for a further 7 DAYS under good growing conditions.
∗ By starting sooner (approx 7 days after rain) the period of maximum stalk elongation has been increased,leading to the potential for increased tonnes of cane/ha.