The July 5th installment of the Louisiana Rice Notes newsletter is now available. This edition covers high nighttime temperatures, bacterial panicle blight, drain timing, and ratoon best management practices.
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The third edition of the Louisiana Rice Notes newsletter is now available. This edition covers planting progress, cold damage to rice seedlings, selecting the correct sulfur and zinc fertilizer for rice, Louisiana rice seeding methods poll results, and a little crawfish trivia. Just click the link below.
By Dustin Harrell
Since writing the article yesterday that discussed estimating nitrogen (N) losses in corn following flooding events (http://louisianacrops.com/2016/03/18/corn-with-all-the-flooding-how-much-nitrogen-have-you-lost/), many new questions have been raised by producers. They are concerned that young corn will need to have the N replaced quickly after the flooding waters drain off fields in order to replace lost N and maximize the yield potential of the corn. This is a valid concern especially if little N is left in the soil after the floods recede or if N has not been applied at all and the corn is reaching the rapid vegetative growth stages. For example, a 200-bushel-per-acre corn crop will take up approximately 200 pounds of N during the growth and development of the crop. Seedling corn, prior to the V6 stage of development (6th leaf collar) will take up very little N, approximately 5% of its seasonal need. However, from V6 to VT (tasseling) corn will take up approximately 60% of its seasonal needs, or about 120 pounds of N for a 200-bushel corn crop. If that N is not available during that rapid growth period (approximately 30 days), then yield losses are certain to occur.
As the flood waters recede, many producers have questions about the best way to replenish the lost fertilizer N quickly to avoid yield losses. Most soils in north Louisiana are too wet to apply N with ground rigs, so that removes the potential to band or knife-in liquid N fertilizers. The only application method currently available to supply a large rate of N is to surface broadcast granular N fertilizer sources such as ammonium sulfate (21-0-0-24) and urea (46-0-0). Urea is less expensive than ammonium sulfate per pound of N; however, it also has the potential to volatilize. The volatility potential of ammonium sulfate is minimal. Volatilization is the conversion of ammonium (a solid) to
ammonia (a gas), which will be lost to the atmosphere. Trials evaluating urea volatility potential of N fertilizers have been conducted at the H. Rouse Caffey Rice Research Station over the past several years. Trials have shown that 30% or more of the N from urea surface broadcast on a dry soil can be lost by ammonia volatilization in a 10-day period of time. Of course, rates of volatilization can vary considerably across soil types. Typically, higher pH soils will have a greater N volatility potential as compared to acidic soil. Treating urea with a urease inhibitor with the active ingredient NBPT or NPPT will protect the urea from volatilization for a given amount of time, depending on soil properties and environmental conditions. In the same studies mentioned above, urease inhibitors greatly reduced ammonia volatility for a 10-day period when applied onto a dry soil. Incorporation of urea into the soil by irrigation or rainfall will minimize volatilization losses. Therefore, if incorporating N into the soil by irrigation or rainfall soon after application is not a possibility, then a urease inhibitor is recommended.
Surface soil moisture will have a tremendous effect on the volatility potential of urea. Typically, urea applied on a dry soil will begin to slowly volatilize initially, but the rate of volatilization really takes off around three days after application. When urea is applied onto a soil that is saturated (without standing water), the rate of volatilization will begin much quicker, and the potential for volatilization losses over a given period of time will be much higher. Figure 1 above, which came from a volatilization trial conducted at the Rice Research Station in 2014, illustrates this phenomenon.
Addition of a urease inhibitor will help in reducing the amount of volatilization losses when urea is applied on a soil without standing water. However, the protection time is generally cut in half. Therefore, the 10-day protection time may only be five days if applied on a moist soil. If the urease inhibitor treated urea is dropped into standing water, the NBPT will not give you any protection.
With all that said, if the soil is too wet for ground equipment and your corn needs N as soon as possible, then you must choose between applying granular ammonium sulfate and urea by air. If urea is your fertilizer of choice, then it is best to wait to apply the N (from an N-efficiency standpoint) when the surface of the soil becomes dry. Applications of urea treated with a urease inhibitor will enable applications onto a soil with a wet soil surface without significant N losses for a few days. Expect large losses of N from urea if it is not treated with a urease inhibitor and it is applied onto a soil with a moist soil surface. Expect even greater losses of N from urea if it is applied into standing water.
The rainfall events that occurred last week have caused tremendous damage to northeast Louisiana farm land due to flooding. In addition to the water received from the rainfall events, some farms were inundated with even more water as nearby bayous and rivers overflowed a few days later. Many of the hardest hit farming operations are still trying to save equipment, livestock, and assets from the rising flood waters. Some farming operations situated on higher ground, such as the Macon Ridge, may have been spared from the flooding but were still affected from the excessive rainfall nonetheless. One of the most commonly asked questions I have been receiving lately is: How much of my nitrogen (N) fertilizer have I lost in my corn crop? Unfortunately, the question is not that straight forward to answer. You really have to consider several factors. What N source did you use? Was it surface broadcast, was it incorporated in after application, was it banded in the soil (knifed-in), or was it dribbled on the soil surface? What was the soil moisture like at the time of application? How long after the fertilizer application did the flooding conditions occur? Was a urease or nitrification inhibitor used? Just to name a few.
Let’s begin by considering the N fertilizer source. First, we need to remember that nitrate-N is not stable under flooded, anaerobic (no oxygen) conditions and that it will be converted to a gas and lost very quickly by a process called denitrification. Ammonium-N, on the other hand, is stable under flooded, anaerobic conditions and will not be lost. Many farmers in northeast Louisiana use granular urea (46-0-0) or liquid UAN (urea ammonium nitrate; 32-0-0) as their N fertilizer source. The granular urea will be converted into the ammonium form after application through a process called hydrolysis. Therefore, if the flooding occurred quickly after urea application, most of the N will not be lost because it will be in the urea or ammonium form and will remain stable under flooded conditions. UAN on the other hand is made up of both urea and ammonium nitrate. The nitrate portion of UAN is approximately 25% while urea and ammonium-N make up the other 75%. Therefore, we would expect 25% of the N that is in the nitrate form to be lost very quickly after flooding.
Now let’s consider the amount of time that the fertilizer N was applied prior to flooding. Ammonium can be converted to nitrate under aerobic (oxygen present) conditions by a process called nitrification. The longer ammonium fertilizer was applied prior to flooding, the more of the ammonium will be converted to nitrate through a process called nitrification. The rate of nitrification depends on several factors including soil type, presence of nitrifying bacteria, and the temperature of the soil. Research has shown a wide range of nitrification rates based on the aforementioned soil properties, so for our purposes let’s assume that the average nitrification rate under cooler soil temperatures (<65oF) would be about 2.5% per day and under warmer soil temperatures the average rate would be at least 4.5% per day.
Another thing we have to consider is whether or not a urease inhibitor or a nitrification inhibitor was applied on the granular fertilizer or mixed in with the liquid N fertilizer. A urease inhibitor (active ingredient NBPT or NPPT) will temporarily delay the conversion of urea to ammonium form (urea hydrolysis) and will therefore temporarily delay volatilization losses (conversion of ammonium-N to ammonia, a gas) and subsequent nitrification reactions (conversion of ammonium to nitrate). Nitrification inhibitors (active ingredients nitrapyrin or DCD) will temporarily delay only the nitrification process. Urease inhibitors and nitrification inhibitors will not last forever. Research at the H. Rouse Caffey Rice Research Station has shown that urease inhibitors will typically give you protection for approximately 10 days when applied on a dry soil, approximately five days when applied on a moist soil, and will provide no protection when applied into standing water. Recent research out of northeast Louisiana indicated that nitrification inhibitors can give you protection 10-30 days, depending on the environmental and soil factors involved.
Using the N source, nitrification rate, and the addition of a urease or nitrification inhibitor, we can begin to estimate how much N will be lost under various scenarios.
Scenario 1. A corn farmer on the Macon Ridge knifed-in UAN at a rate of 200 pounds of N just after planting. The UAN was not treated with a urease or nitrification inhibitor. Saturated soil conditions occurred 12 days after planting and lasted for 2 days. The soil temperature was <65oF. How much N was lost?
Well, we know right away that 25% of the UAN is in the nitrate form and will be lost under saturated, anaerobic conditions. We also know that we have had 12 days for nitrification (conversion of ammonium to nitrate) to occur in a cool soil and that a nitrification or urease inhibitor was not used, so the nitrification rate will be about 2.5% per day.
Therefore, the N loses from denitrification = (0.25 * 200 lb N/A) + (12 days * 0.025 * 200 lb N/A) = 80 pounds of N per acre lost.
Scenario 2: Granular urea (46-0-0) was treated with a urease inhibitor and was applied on moist ground 3 days after planting at a rate of 50 pounds N per acre. A one-half inch rain occurred 2-days later that incorporated the urea into the soil, minimizing volatilization (ammonia gas) losses from the urea. Flooding conditions occurred 15 days later and the field stayed under water for four days. The soil temperature was <65oF. How much N was lost?
This time all of the N is in the urea form to begin with and was protected from volatilization losses prior to the small incorporating rain. However, the urease inhibitor probably only kept the fertilizer in the urea form for approximately 5 days before it was converted into the ammonium form. Nitrification (conversion of ammonium to nitrate) could then occur for about 10 days.
Therefore, the loss of N from denitrification = 10 days * 0.025 * 50 lb N/A = 12.5 pounds of N per acre lost. In addition, I would expect that the corn would not be able to survive this situation and would have to be replanted.
Remember, these N loss estimates are not perfect. There are a lot of factors involved in estimating N loses that were not covered and it could be argued that the rates of nitrification or the time that a urease or nitrification inhibitor could differ depending on the research you use as your source. However, it is a good starting point and should help growers in northeast Louisiana determine how much N will be available in the soil once saturated soils dry and flood waters recede.
Dr. Michael Deliberto made a presentation at the Louisiana Agriculture Technology & Management Conference last month which was excellent! When rice prices are down, producers tend to try to reduce expenditures on seed and fertilizer. One of the major points that he made was that, because fertilizer and fuel costs are down, the overall cost of production for rice is down. See Dr. Deliberto’s slide below.
As an agronomist, I am going to encourage you not to cut back on fertilizer and sacrifice yield when fertilizer costs are the lowest we have seen in years! Dr. Deliberto explains the economics of this in more detail below.
As commodity prices remain lower than levels witnessed the prior year, producers will be faced with making critical farm management decisions to improve profitability. Such decisions may be determining way(s) to increase crop yields to offset a slumping market price and/or reducing the cost of production. The latter will likely have the most apparent effect. For CLEARFIELD® rice, the projected variable cost per acre in 2016 is estimated at $551.72. This is a reduction of $31.54 from the estimated $583.26 cost of a year prior, and a continuation of a four-year decreasing trend in overall rice production costs.
The fertilizer recommendation, as contained in the projected costs for CLEARFIELD® rice that is drill planted in southwestern Louisiana, is 130 pounds of nitrogen (N), 40 pounds of phosphate (P), and 60 pounds of potash (K). Over the past decade, fertilizer costs in rice represent approximately 19% of the total variable cost per acre. This dollar amount can vary from $76.30 to $149.10 per acre, with the maximum amount being imposed during the 2009 crop year. This was a year in which the price per pound of P and K were at record levels.
Figure 1 illustrated the price per pound of active ingredient for N, P, and K fertilizers as contained in the Louisiana rice enterprise budgets. For 2016, the fertilizer expenditure is $98.50 per acre, consistent with a 130-40-60 fertilizer prescription.
Nationally, fertilizer prices have declined by as much as 20% from a year earlier. The cost of urea during the week of February 9, 2015 was $473 per ton. During the week of February 8, 2016, the DTN retail survey reported the price was $369 per ton. This represents a $104 (21.9%) reduction in unit cost. Di-ammonium phosphate, referred to as DAP, decreased from $569 to $479 per ton over that same time period. This is a $90 (15.8%) reduction in cost. Potash also witnessed a price decline, from $488 to $378 per ton. Potash decreased by $110 per ton (22.5%) over the past calendar year.
Figure 2 present the national retail price per ton for urea, DAP, and potash.
The 2015/16 average farm price for long and medium-grain price received downward revisions in both the January and February USDA World Agriculture Supply and Demand (WASDE) estimates. Midpoint price estimates are $11.30 and $12.00 per hundredweight for long- and southern medium-grain rice, respectively.
I sent out a poll question on Tuesday (March 8) to get an idea about how much rice was planted in the state. Two questions were asked.
The response from the text message group was very good. I had a total of 54 responses from farmers and crop consultants. Some responses contained answers to only one of the questions, either the acres planted or the percent of acres planted. So, there will obviously be some error in the reporting of the results. Nonetheless, here is what we found out…
The poll reported approximately 39,000 acres planted by those responding to the text. That alone is 9% of the total planted acres in 2015. Remember, this is all rice that was planted before the March 10 recommended planting window and only from a small subset of responding rice farmers!
The largest amount of acres planted by one farming operation was 3,000. Of the 54 responses, 19 farming operations (35%) have not started. One producer told me that they wanted to use all of their resources to work and level ground during the dry period before the rains and then worry about planting when it dries again.
Several producers mentioned that all of the planted acres were drill-seeded and that they planned to water-seed some rice after the rains. Therefore, we may even see a significant increase in acres in southwest Louisiana next week, even if the soils do not dry out completely.
The average number of acres planted by all those reporting was 743 acres, while the average number of acres planted by only those who had some rice in the ground was 1,175 acres. The average number of rice acres per farming operation planned for 2016 (only by those that reported percentage of acres planted) was 1,592 acres.
The weather this winter was really quite mild overall. In addition, warm spring temperatures arrived early this year. Due to this warm weather, rice planting in southwest Louisiana began in earnest the last week of February with several hundred acres being drill planted (where the soil was dry) before the first day of March.
The recommended planting window for rice in Southwest Louisiana is March 10 – April 15, while Northeast Louisiana is April 1 – May 5. However, it is hard to wait on a recommended planting date on a calendar when the weather is favorable for planting now and cooler temperatures are not in the foreseeable future forecast. This year is quite a contrast from last year, where rice planting did not really start until the third week of March due to the continuous rainfall and wet soils.
This year, by the first weekend in March (5th and 6th), many rice farmers were planting at full speed. The only problem with this was the looming rain storms that were moving into the area and the potential for several inches of rain and the possibility for flooding over the next several days. As of Friday morning (arch 11), the Southwest Louisiana rice production area has received some rain, but it has really not been that excessive.
However, the rice production areas in Northeast Louisiana, Arkansas and Mississippi, have received excessive rainfall totals this week. One producer in Northeast Louisiana reported rainfall totals on his farm were in excess of 23 inches between Tuesday and Friday morning!
While no rice planting has been reported to me in Northeast Louisiana, there has been a lot of corn planted. While seedling rice can survive up to 10 days in submerged conditions, corn seedlings up to the 6-leaf stage of development can generally only survive 2 days under these conditions. Dr.
Dan Fromme, the LSU AgCenter’s corn, cotton, and grain sorghum specialist wrote a great article about flooded conditions on corn which can be accessed here:
If corn stands are lost and additional seed is unavailable, or if the soils remain wet for and extended amount of time, some of this corn acreage could possibly go into soybeans or rice. This will possibly have an effect on our overall rice acres in the state.