Friday, September 17, 2021

Managing submerged rice or a lost flood

• By Jarrod Hardke •

“At some point it can’t get any wetter, it can only get deeper.”  The south half of Arkansas is feeling that statement this week. Torrential rains struck areas of east-central and southeast Arkansas with places like Dumas seeing 18 inches or more.  This week turned into one of crop and field destruction south of I-40 (not to mention homes and businesses), while rains scattered the northeast region.

Either way you slice it, by and large, it’s another week lost for management progress on this crop. One could argue it’s one step forward in time, two steps backward in management.

Washed out and busted levees are the most widespread rice concern in heavy rainfall areas, and in all areas attempting to fertilize and flood aging rice is reaching a critical point. However, there are more rice acres that are completely submerged and need drainage quickly.

Mild conditions may work in our favor for managing these issues, but lack of pushing the crop forward will only push the harvest window further back. Temperatures appear ready to finally take off this week, increasing the need to manage this crop quickly to stay on track.

Fig. 1.  AHPS Observed Precipitation for last 7 days (6/11/21).

AHPS 7-day precipitation

Managing rice submerged or flood lost

• By Jarrod Hardke and Trent Roberts •

Submerged Rice

With all of the rain experienced in south Arkansas this week, the questions certainly turn to rice survival. Rice is semi-aquatic and tolerates a flood but does not like deep water and submergence.

It all depends on the overall conditions, but the condition of the floodwater is a key component. While there are no real management recommendations other than ‘get the water off’, here is some of what you can expect on rice survival which may influence your efforts on which fields to work hardest to remove water from.

Younger rice, still in the seedling / tillering / vegetative stages, can survive for long periods of time under submerged conditions.  When conditions are mild, and the floodwater is cool and moving, we’ve seen rice survive submergence for a month.  However, we’ve also seen rice die in a week when floodwater conditions are deep, muddy, and stagnant.

Older rice at midseason or around joint movement / reproductive growth is more sensitive to being submerged. If submerged for less than seven days, it generally survives but there may be issues with it laying over as the water goes down and need time to stand up.

In the seven- to 10-day window, survival can be a coin flip.  As we approach 10 days or more of submergence, the outcome is usually bad and plants die.  Keep in mind these comments are based on years of observations of flooding events that have occurred and have been the most common responses, hopefully most fields will beat the odds.

Fig. 2.  Completely submerged rice field.

Submerged rice field

Flood loss

Fields that had already been fertilized and flooded, but now have washed out levees, pose another problem. Some will be straightforward repairs, but others are extensive. Whether you have lost nitrogen is a highly variable situation.

If you’ve been flooded for around three weeks then any N loss will be minimal or nonexistent when you reflood (you haven’t lost N just because you lost the flood). Just get the flood back on as soon as you can and keep going to avoid allowing fields to dry too much and stress in early reproductive stages.

If you’ve only been flooded a short time and after repairs will be reflooding prior to 3 weeks since initial flood, N loss could happen. However, it is advised that you do not automatically add N at this stage.

You are far better off to reflood and then monitor the crop as it continues to progress.  Unnecessary N applications will only increase our cost and exaggerate management issues. After the flood has been reestablished monitor for potential N deficiencies or use the GreenSeeker to determine if and when more N may be needed. Work has shown that rice yield can be recovered or increased with midseason N applications as late as three weeks after panicle initiation (green ring).

Fig. 3.  Rice levee and MIRI pipe washout with flood escaping.

washed out levee

Dr. Jarrod Hardke is University of Arkansas Extension rice agronomist. He may be reached at jhardke@uada.edu Dr. Trent Roberts is a University of Arkansas associate professor of soil fertility/soil testing.

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