Recent research evaluating the use of sodium chlorate as a harvest aid in hybrid rice have largely confirmed previous recommendations. Previous studies focused on varieties, so this work was conducted specifically on a hybrid (RT XP753) to ensure the results lined up.
Generally, varieties and hybrids seem to respond similarly to being salted.
The existing recommendation is to wait until rice is below 25% grain moisture before making a sodium chlorate application, then pull back on applications once rice falls below 18% grain moisture.
Harvest should occur within 4 to 5 days after application. The data for grain yield and head rice yield largely agrees with that recommendation.
If you look very closely into the details of the data, there seems to be more risk of loss associated with salting a hybrid (XP753 in this case) when grain moisture is 23% or greater.
So for now, I recommend waiting until hybrids are below that point before salting. Another consistent outcome is that if rice left for longer than 4 to 5 after application, you can expect a negative impact in both grain yield and head rice yield. Bottom line: if you’re going to spray it, hurry up and cut it.
One thing noticeable between old data and this data is that small plot combines continuously show a slight yield reduction between the control and treated plots.
This is likely due to the impossible nature of adjusting air speed and reel speed from plot to plot as the operator jumps from higher to lower moisture rice. This is something a commercial machine in a large field can readily address.
Herbicide and Desiccant Drift on Maturing Rice
A number of Arkansas and Mississippi studies have examined the effect on maturing rice from various soybean herbicides and desiccants.
This time of year with rice trying to finish up and much being drained, many people apparently assume that rice has moved past the point of injury at that stage. That is wrong.
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The general theme, regardless of the data source, is that paraquat or sodium chlorate drift onto through late stages of development (soft dough, hard dough, draining) can still cause yield loss.
These two desiccants can cause 10% to 20% yield loss at these times, occasionally more. Glyphosate and glufosinate herbicides are a little different. Both can cause rice yield loss if drift rates are high enough and rice is heading or in the boot. Yield loss is usually only slight if rice is soft dough or later – but the response varies, so that’s still not safe.
Take home message: rice is still susceptible to yield loss, sometimes major, until it’s fully mature. Avoid drifting soybean herbicides or desiccants onto rice to avoid yield loss.