June 5, 2014 No. 2014-13
Dr. Jarrod Hardke, Dr. Rick Norman, & Dr. Bob Scott
What’s done is done and the future is now. It’s possible someone was able to squeeze in a few more acres of rice this past week, but either way rice planting should now be complete.
The real story right now is that according to DD50 enrollment, 75% of the rice in the state should be fertilized and flooded right now (Table 1). Unfortunately only about 30% actually is. The added problem – according to DD50 we’re on the fast train toward internode elongation (Table 2). On a more positive note – delays in preflood nitrogen application and flooding typically cause rice to develop slower than predicted in the DD50 – so you have more time than you think you do. However, the time to act is now. To add insult to injury, the long-term forecast shows rain chances of 30-60% over the next 7-10 days. This is absolutely not what we need right now. See Page 2 for more on making fertilization choices on a case-by-case basis.
For those wondering what the current acreage breakout by cultivar is, see Table 3. CL XL745 is the most widely planted cultivar followed by Jupiter and Roy J. Obviously growers found medium grain seed – that number puts the state at over 200,000 acres of medium grain rice planted.
Enroll fields in the DD50 Program here: http://DD50.uaex.edu.
Problems or questions: firstname.lastname@example.org / 501-772-1714.
Table 1. Percent of rice acres set to reach permanent flooding during listed weeks of 2014 according to current DD50 enrollment.
Table 2. Percent of rice acres set to reach internode elongation during listed weeks of 2014 according to DD50 enrollment.
|June 29 – July 5||16%|
Table 3. Arkansas rice acres by cultivar for 2014 according to DD50 enrollment.
Nitrogen Fertilization Management in Troubling Times
For most rice fields, they haven’t reached the end of the world yet – but you can see it from there. The story right now is that many want (desperately need) to apply preflood nitrogen (N) and establish a permanent flood. The problem is that wind and rainy conditions have prevented us from making needed preflood herbicide applications and preflood N applications – again and again. So now many find themselves up against the final recommended time to apply preflood N.
Rice plants take up about 60% of preflood N applied. Each of the first 3 weeks after permanent flood rice takes up 10%, 20%, and 30% (to total 60%) of N applied. From the optimum window to apply preflood N until internode elongation (IE) is about 3 weeks. From the final recommended time to apply preflood N to IE is about 2 weeks. Keep in mind that with delays in preflood N application and flooding, the plant does not usually grow as fast as predicted – meaning it will take the plants longer to get to IE than predicted by DD50 and you have more time.
Regardless of your situation, if you have time to wait to attempt to apply preflood N onto dry soil then do it. Resorting to applying N onto muddy soil or into standing water are not favorable options unless we’ve run out of time.
Keep in mind that we can’t truly make up for lost yield with N applied at midseason. If the plant didn’t have the N it needed earlier, midseason N may only contribute 15-20 bu/A.
Here are the options, listed in order of preference based on yield response and N efficiency:
- Field is dry: Apply NBPT-treated urea onto dry soil and establish the permanent flood to incorporate N below the soil surface.
- Field is muddy: Apply NBPT-treated urea onto muddy soil and attempt to let the soil dry. If a significant rainfall event occurs – flood the field; otherwise let the soil dry before establishing the flood. If you’re putting it out on mud and feel the need to slightly bump the N rate (maybe 10 lbs N higher) it may or may not help, but no argument here. Do it if it makes you feel better.
- Field has standing water: Get the water off if you can, but if you are out of time and can’t – “spoon-feed” N into the flood in small quantities every 5-7 days for 4 weeks (or until internode elongation). Small quantities means 45 lbs N/acre (100 lbs urea/acre). If you have less time to IE, maybe applying N for 3 weeks at 45, 60, and 60 lbs N/acre will be better. However, smaller quantities applied more frequently are your best option in this situation. Do not for any reason apply the entire recommended preflood N rate into standing water.
Table 4 shows some research into these recommendations. Dry soil is the best situation to apply preflood N. However, if we’re forced into a muddy soil situation, using urea treated with NBPT or ammonium sulfate is the best option.
Table 4. Influence of preflood N source and soil moisture on rice grain yields (bu/A).
|N Source||Dry Soil||Muddy Soil|
|Urea + NBPT||199||182|
* N source applied 3 days prior to permanent flood at 4-5 leaf stage.
Call about specific questions / situations.
Out Standing in Your Field
A few days this week were absolutely prime time for making herbicide applications (Picture 2). Unfortunately, as you’ve probably read or heard about, herbicide shortages are making weed control recommendations very difficult right now. Options are becoming very limited and in some cases we may not have the tools we need to get some situations under control.
The past two weeks have been filled with problems to look at and weather conditions have played a major role. A number of fields are showing possible deficiency patterns out in weird shapes and patterns in the field (not unusual for deficiencies but some of these take the cake).
Picture 3 shows a field where the problem was obviously the result of a ground-based activity – unfortunately virtually everything done in the field was by air. A lot of time was spent looking at every possible cause of the problem. Deficiency symptoms were evident so we collected tissue and soil samples and were on our way. The farmer called soon after and he had figured it out – the duals on his tractor at planting were the repeated pattern we were seeing across the field. Apparently compaction (or lack thereof) at planting combined with the weather led to irregular health of his crop. We’ll see what the tissue and soil analysis says but this one is strange.
Picture 4 is in here just to show a common indicator of Newpath drift. Oftentimes Newpath and glyphosate drift symptoms can be confusing, but finding a large, healthy plant randomly in the middle of a drift event is a safe bet that it’s a Clearfield off-type in the field. In other situations it can be more difficult to tell the two apart.
Picture 5 was taken in a different section of the previous field. It looked as though Facet was having an effect on occasional plants in the plant. Nothing too serious was going on, but this can happen from time to time. A little “buggy-whipping” and twisting of new tillers.
Several calls have been about possible herbicide carryover situations. Picture 6 shows a definite carryover and the soil samples confirm plenty of Newpath in the soil. The field is up and down and we’ll have to monitor to see how it responds.
Picture 7 is suspected fomesafen carryover – suspected because it’s hard to know what carryover from this herbicide looks like in rice. Attempts to create the situation in research plots hasn’t worked out. So at this point it’s unknown if it’s real or not, but I can say that in several of these fields, the herbicide was used at “hot” rates late in the soybean season and the rice was planted early inside the 10-month plant-back interval.
Zinc deficiency (Picture 8) has been a common suspect with the frequent saturated soil conditions. Zinc deficient plants have been confirmed in a few situations but something else was probably going on because soil tests were adequate. Usually there were other problems in these fields and the areas of concern – standing water most often. Warmer, sunnier conditions generally resulted in improvement the fields without action. The deficient plant pictured here was one that happened to show true long-term deficiency symptoms (bronzing and a bright yellow midrib on the lower leaf).
Picture 9 shows some glyphosate drift that was found on random plants in a field. The randomness suggests tank contamination rather than drift. The twisted leaf was the giveaway – which actually looks a lot like a wheat flag leaf after glyphosate drift.
Some changes have been made to the online DD50 Program this year. Hopefully these and future changes will continue to make the program easier and more efficient to use. If you have any questions, or suggestions for improving the program, please let us know. You can access the online program here: http://DD50.uaex.edu/.
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We sincerely appreciate the support for this publication provided by the rice farmers of Arkansas and administered by the Arkansas Rice Research and Promotion Board.
The authors greatly appreciate the feedback and contributions of all growers, county agents, consultants, and rice industry stakeholders.