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Arkansas rice crop update for the week of April 23, 2012

The Rice Update is a weekly summary of what’s happening and what to look for in rice production, based on interviews and submissions of rice experts in Arkansas and the Mid-South.

Weather:  The forecast in Eastern Arkansas for the next 10 days is continued dry, lows in the 60s (this weekend may drop into the upper 40s in the northeast, 50s rest of Delta) and highs in the low 80s (except this weekend).  In general, temperatures are projected to be warmer than recent days and better for rice growth.  Many areas report rapid drying with past weekend winds through Monday and no serious rain chances are forecast until about May 3 or so, although there is a slightly better chance starting Friday of this week, but unlikely.  In areas where rice was planted and received rain last Friday, the crop had started to spike then stopped due to cold weather, and the wind dried out the fields by Monday night.  These fields may need to be flushed soon, believe it or not.  Spiked rice is sensitive to soil drying and crusting, which is happening now in some fields, and flushing can save the stand or even it out.  Flushing is a recognized pain, but it feels better when it is over and you have a nice stand of healthy rice.

Dr. Chuck Wilson, Director of the Rice Research and Extension Center and Rice Agronomist, University of Arkansas Division of Agriculture:

There has not been much change since last week.  We have 90% of projected rice planted, and many farmers have switched to soybeans.  Rain last Friday helped even up some fields and activated herbicides, but the cool temps over the weekend have been holding emerging rice back.  These conditions may complicate weed control a bit, given the windy conditions that kept applicators out of the fields over the weekend and today (Monday), but forecast conditions are for warmer and calmer weather and should allow us to catch up on weed control a bit.  Urea prices continue to be out the roof and are strongly encouraging soybean production.

Dr. Bob Scott, Professor and UA Division of Agriculture Extension Weed Scientist:

This is an odd year; as I get older I seem to be saying that every year though.  We have rice just planted to some fields being ready to flood, believe it or not, so weed control calls are all over the place.  Big grass continues to be a challenge in a few fields.  In several fields, rice is just germinating to one leaf with no pre-emergent herbicide application or activity due to the lack of rain or no flush on the field, so we end up with 3-4 leaf grass among 1 leaf rice.  This is a very difficult situation in fields with resistant barnyardgrass populations.  We are already using Ricestar which is an expensive option that usually fits pre-flood timing better, but where the pre was not used or activated, this is one of the options, albeit expensive, that we have to use.  There is a huge difference in rice growth and uniformity, and cleanliness, where farmers were able to flush in the pre.  These fields really shine this year.

Permit Plus is a new formulation of Permit + low rate of thifensulfuron-methyl (Harmony), and it is very good from prior to rice emergence to post flood and is very effective on smartweed and nutsedge.  We have had lots of calls about applications going out recently.

Another new product from Valent is League, being used for broadleaf weeds and with Command for weeds and grass.   It also wipes out annual sedges.

In Clearfield systems, we have early post to pre-flood applications being made.  In some fields, grass has come through the pre or command.  On 3-4 leaf grass, Newpath is adequate early post, but Facet is being added where grass is bigger than 4 leaf.  Some growers had concerns about spraying the Clearfield hybrids during recent cool conditions, and if the fields were relatively clean or weeds were really small, it does not hurt to wait a couple of days to let temperatures recover and warm up a bit.  If weeds are getting out of control, my advice was to go ahead and treat, although night temperatures in the 40s (rice won’t grow) still scare me a little on certain hybrids but we should manage.

Overall, we are doing OK in the weed control world on this rice crop.

Northeast Arkansas – Johnny Wheetley, Consultant

My growers planted quite a bit more RoyJ than last year and right now it is up and looks OK.  We are about 90% planted, and I expect the rest of our growers to finish rice planting this week.  I probably have 25% RoyJ, 15% XL745 and XL729 hybrid combined, 10% CL142AR, one field of CL111 and the rest in CL151 and CL152.  I have more CL152 than anticipated, as growers found seed.  In our earliest fields we battled grass because Command applications went about two weeks without activation, but after rains in the area, it reached back and took out a lot of grass.  We have used other herbicides to catch up on some of the conventional fields with grass problems.  During the cool weather, we held off on applications of Newpath for a couple of days on Clearfield hybrids to let things warm up and avoid any potential injury, mainly on the cleaner fields.  Urea is still very high in the area. We are hoping for some drop in price later, but some farmers may not be able to wait.  This is very discouraging to rice farmers at present.

Greg Jones, Consultant:

Late last week I noticed leaf spotting on several hybrid fields, especially on the lower leaves.  Dr. Wamishe is looking into the possibility of injury from paraquat drift but does not think it is a disease like brown spot.  We are still not sure what it is, but it is widespread in some fields.  My growers are mostly planted with about 70% emerged.  Fields planted the third week of March look good, those planted very late March to early April are skippy at present but rains late last week should help.  A few fields have weaker stands but are manageable.  First Command applications did not work well due to dry conditions but subsequent herbicide applications have worked, and weed control is ok for the most part.  There has been quite a bit of respraying due to lack of activation.  My growers planted mostly hybrids, including XL745, XL729, some 753 and 756, and we have scattered fields of Francis, RoyJ, Taggart, Cocodrie, CL151 and CL111.

Randy Chlapecka, County Extension Agent- Jackson County:

We are 95% planted and off to a very good start, the best start in a long time.  In our area, we had periodic rains after planting with good activation of pre herbicides and good weed control in general.  We likely have about 50% hybrids with mostly XL745, come CL151 and CL111, quite a bit more RoyJ than I expected and scattered acreage of Wells, Francis, Taggart and Jupiter (although the latter has dropped off since last year).  We have no huge problems, but recent cool weather slowed the crop down.  Urea is very expensive and some growers are considering ammonium sulfate, or at least mixing some in.

Jason McGee, Rice Consultant, Cross and Poinsett Counties:

Pythium damage recently showed up, especially is some fields of Wells.  Hopefully, warm weather this week will help correct this problem.  It was 42 degrees Monday night.  Some of planted rice spiked after rains last Friday and has just set there since so we have to get it moving again.  We had to make a lot of supplemental herbicide applications in fields for grass and smartweeds where the pre was not activated well earlier.  Some farmers are planting STS Stacked soybean varieties around rice fields where Permit Plus will be used.  Jupiter fields look pretty good while RoyJ looks OK on our white dirt fields but is really struggling on the gumbo (clays).  CL151 will make it but is off to its normal rough looking start.  Hybrids are skippy and thin and have been sitting there during the cool spell, but we expect them to recover soon.  Urea prices are killing us.

East-Central Arkansas – Brent Griffin, County Extension Agent:

We had a north wind this weekend and a south wind on Monday so some fields are crusting over, making further emergence a problem.   The cool temps did not help.  We will start flushing by Thursday to get things moving again and even up stands more.  We have a lot of hybrid acreage and early XL745 fields look good; 751 looks good; 729 is skippy in a lot of fields, and 753 looks pretty bad in places.   Some growers expressed concern about the appearance of the seed for the latter when planted.  A few fields we checked only average about 2 plants per square foot, and growers are pretty concerned about these but plan to keep them.

The CL111 fields I have looked at are beautiful and they are “going to town”; CL151 and CL142AR look good as well; RoyJ fields look OK but blackbirds thinned some of them out earlier.  Seed planted in the moisture came up well recently, but some fields are still erratic.

“The cheese is binding” for growers who planted after April 10, then it cooled off, now soils have dried out again and we need a rain or flush to bring it all up, but they plan to flush and get things going.  This should relieve their tension.  It is amazing that we got 1.2 inches of rain last Friday and are going to have to flush rice later this week.

Southeast Arkansas – Gus Wilson and Wes Kirkpatrick, County Extension Agent:

Most rice fields look good although our acreage is down considerably.   Any planted now will need a rain immediately to come up.  Weed control is in good shape for the most part.  The wind has been terrible and dried out lots of fields pretty fast.  We are starting to water corn already.  Another inch of rain this weekend would be appreciated.

Armyworms ate 3 acres of rice near a wheat field they were marching out of the past few days, and we have had a lot of worms in pastures.  They seemed worse last week and have slacked off somewhat over the weekend it appears.

Soybean and cotton planting are full bore currently, and urea prices continue to kill attitudes for rice, corn and cotton growers.

The wind has complicated herbicide applications recently, and we need calm weather to catch up.  Pigweeds are a major concern already, with some weeds already heading and setting seed.  While crops were planted and emerged far in advance of normal, so did the pigweeds. This is going to be a battle all year, and some growers are already concerned about being behind.

Dr. Trent Roberts, Assistant Professor and leader of the N-ST*R Program:

We have received several questions following last week’s article in Delta Farm Press concerning the use of UAN 32% as a N source for rice. To review some fertilizer basics, let’s start out with what UAN 32% is. Urea-Ammonium-Nitrate 32% solution is a commonly used N fertilizer source that contains~ 16% urea (good for preflood N in rice), ~8% ammonium (good for preflood N in rice), and ~8% nitrate (bad for preflood N in rice) and is most widely used in the Delta to meet the N requirements of corn and cotton. As mentioned, UAN 32% is a liquid and is commonly knifed in using an applicator that places the solution below the soil surface to help eliminate the potential for ammonia volatilization losses and place it near the crop’s rooting zone. Just like granular urea, the urea dissolved in UAN solution is subject to ammonia volatilization losses if conditions are suitable (i.e. high pH soil, wet soil, high temp., high winds etc.) and in some cases has been shown to result in higher ammonia volatilization loss potential.  There are two common reasons why UAN is often mentioned for rice, distribution of fertilizer N and the price per lb of N.

When applying granular urea, even distribution of fertilizer N is often cited as one of its largest drawbacks aside from the ammonia volatilization loss potential.  One benefit of UAN 32% is the ability to evenly distribute N fertilizer over the entire crop- even at high rates. For anyone that has had rice field streaked this may sound great, but unfortunately the risks far outweigh the rewards when considering UAN for rice. Research has shown time and time again that ammonia-based fertilizers (urea and ammonium sulfate) are the most efficient N fertilizer sources for direct-seeded, delayed-flood rice production. Properly managed pre-flood N (as urea) allows the fertilizer to be incorporated into the soil using the floodwater and protect it from loss mechanisms such as volatilization and nitrification/denitrification. Why is nitrate not suitable for pre-flood N application in Arkansas rice? Aside from its leaching potential the main issue associated with the use of nitrate in direct-seeded, delayed-flood rice production is the conversion of nitrate to various N gases (nitrous oxide, N2 etc.) under flooded or anaerobic conditions. This essentially means that when using UAN, the flooded conditions that would normally protect granular urea and the urea in UAN are actually contributing to the loss of nitrate contained in the UAN solution. Work conducted here in Arkansas by Chuck Wilson and Rick Norman using N15 tracers resulted in <10% recovery of nitrate from UAN solution compared to greater than 80% recovery of N from granular urea by the rice plant. As outlined in the MP-192 (Chapter 8-Efficient Use of Fertilizer), the best and most economical source of N for rice is urea, followed by ammonium sulfate and UAN 32% is last. Now let’s take things a step further by looking at the economics of rice fertilization based on cost and efficiency. Based on the work of Wilson and Norman, the relative efficiency of properly managed granular urea is ~70%, whereas the overall efficiency of UAN 32% is ~41%. If we take the cost per lb of N and consider the uptake efficiency of these two N fertilizer products the cost of UAN 32% is far greater than that of urea. Another issue with the use of UAN 32% that is commonly overlooked, at least initially is availability of the product and means of application. Although UAN 32% looks good initially based on the price, when you consider all of the factors it is really not a suitable option for pre-flood N. If UAN 32% was a viable and cost effective N fertilizer source for rice we would use it all of the time-not just when urea costs get high.

The following table shows the estimated cost of fertilizer, N analysis, uptake efficiency based on N15 tracer studies conducted at Stuttgart, AR and the relative cost of N based on the uptake efficiency of the fertilizer product.

Fertilizer Source

Analysis (%N)

Uptake Efficiency

(% in rice plant)

Cost per lb N

Cost per lb N in the rice plant

Urea ($750/ton)

46%

70%

$0.82

$1.17

UAN 32% ($400/ton)

32%

41%

$0.63

$1.54

 

Please direct any comments, questions or concerns to Dr. Rick Cartwright, who can be contacted at rcartwright@uaex.edu .


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