- Specialists Speaking -
Timely flood is key
Dr. Nathan Buehring
Urea cost over the recent years has continued to increase. The last price I received on urea was approaching $500/ton. Every year the cost of urea continues to increase, and rice producers continue to ask, “Can I cut back on urea since it cost so much?” Even with the cost of urea close to $500/ton, the answer once again is no (unless you are above our current recommendations). Nitrogen (N) is a vital component to producing excellent rice yields. It is a necessary nutrient to get the most return on your rice crop.
As a rule of thumb for current varieties grown in Mississippi, we recommend a total of 180 lb N/A for clay soils and 165 lb N/A for silt loam soils. For semi-dwarf varieties (Cocodrie and Sabine) on clay soils, we recommend 120 to 150 lb N/A applied preflood, then followed with 30 to 60 lb N/A at midseason. For varieties that are susceptible to lodging (CL161 and Wells) on clay soils, decrease the nitrogen rate to 90 to 120 lb N/A at preflood, followed by the remaining N at midseason to help reduce the potential for lodging. On silt loam soils, we recommend 120 lb N/A at preflood and 45 lb N/A at midseason for varieties such as Cocodrie, Sabine and Wells. For CL 161 and Francis, we recommend 90 lb N/A at preflood and 60 lb N/A at midseason.
The key to getting the most out of your nitrogen is a timely flood. Ideally, we would like to have a flood established within five days after the nitrogen has been applied. Getting a flood established outside that five-day window can lead to nitrogen loss due to volatilization. If you find yourself outside that window, there are a couple of things to help prevent losing valuable nitrogen. First, consider multiple-inlet irrigation. This will help get the flood established quicker and allow for more flexibility in your irrigation program. The second thing to consider is using Agrotain-treated urea. Agrotain protects urea from volatilization up to 10 days after application and is the most beneficial on areas of the fields that are not flooded within five days.
Phosphorus is another essential element to consider in a fertility program. However, with the price of diammonium phosphate (DAP) exceeding $700/ton, rice producers are trying to figure out if they really need to include phosphorus in their fertility program. That is a question I cannot answer without having a soils test report in front of me. In years past we have often found ourselves shooting from the hip on whether or not a phosphorus application is necessary. But, with 100 lb DAP application approaching $35/A, everyone is rethinking their strategy. Now, more than ever, having a soil-testing program on your farm makes dollars, not cents, because one $6 soil sample can possibly save you over $35/A.
This spring, before planting season begins, I would spend a day riding around and collecting some soil samples. From this, you will certainly have a better idea of your phosphorus levels and whether or not you need to make a phosphorus application.
Where phosphorus deficiency problems are highly likely, the best time
to make an application is from the 1- to 5-leaf stage. DAP (18-46-0)
at 100 lb/A could supply enough phosphorus as well as supply early season
nitrogen for improved vegetative growth.
the N rate to the crop
Dr. John Saichuk
It is not news to anyone involved in production agriculture that input costs have risen dramatically in the past year. Despite the increase in rice prices, the question remains, “Can we afford to grow rice?” As I mentioned at some of the producer meetings, lenders may go into shock when they look at the amount of money needed to put in a rice crop this year. Certainly rice has to be among the most expensive agronomic crops to grow.
According to Dr. Dustin Harrell, agronomist at the Rice Research Station in Crowley, urea and triple super phosphate (0-46-0) were quoted to him at $525 per ton, up $162 and $189 per ton respectively from 2006 to 2007. Potassium is just as shocking at $425 per ton or up nearly $180 per ton over the last two years. By the time you read this, the prices may be even higher.
Nitrogen is the most expensive fertilizer component in rice production. In our publication, Rice Varieties and Management Tips 2008, we provide nitrogen recommendations by variety. In each case there is a range of nitrogen rates. This is because there is a great deal of variation in nitrogen response by variety, by year and by soil type. The more you know about the response of a particular variety on your farm, the more accurate you will be in determining the amount within the prescribed range to optimize nitrogen use.
Dr. Harrell examined some of his data experimentally to answer the question, “Can we cut back on nitrogen rates and still produce a good crop?” He set up two situations. In the first scenario, urea cost $525 per ton, and rice sells for $14 per hundredweight. The optimum nitrogen rate for the variety in question calculates to 160 pounds of urea per acre. When he changed the price of urea to $600 per ton and dropped the rice price to $10 per hundredweight, the optimum nitrogen rate dropped to 154 pounds per acre. So his answer to the question of cutting back is, “Not really.”
In our experience in the Rice Research Verification Program over the past 10 years, we seldom cut nitrogen rates. We use the published recommendations; take into account the yield history of the farm or even the area and the variety. Then we set an amount. We recommend applying about 2/3 to 3/4 of the total just ahead of permanent flood establishment. At internode elongation (green ring) we either apply the remaining amount or adjust the rate to compensate for any changes that may have occurred since the first application was made. If plants start showing nitrogen deficiency before green ring and growing conditions look good, we usually add a few pounds to the original target amount. If it is raining every day with an outlook for lower yields, we may back off of the initial intentions. We do not try to “cut costs;” we simply try to adjust the nitrogen rate to the crop.
Phosphorus and potassium needs should be determined by a soil test. Most of the Mississippi River alluvial soils require little or none of either. Farmers in those areas are lucky. Often the Red River alluvial soils will test very high in phosphorus and potassium, but because of high soil pH, we have encountered phosphorus deficiencies regularly in recent years. The loess and old alluvial soils of the southwest Louisiana rice-growing areas almost always require both phosphorus and potassium, but the only way to know with certainty is to use a soil test.
Last year, we encountered a couple of cases of what appeared to be either potassium deficiency or a late-season sulfur deficiency. We took tissue samples from affected and “normal” areas of the fields and analyzed them. We also recommended an application of additional potassium to the field. Tissue analyses showed both nutrients to be below normal with potassium more deficient than sulfur. In each case, special circumstances had more to do with the problem than lack of fertilizer. Most of the time nutrient deficiencies go unnoticed because they are not severe enough for symptoms to be manifested. In many cases, the only symptom is lower yield, which without other corroborating symptoms is never detected.
I remember an old joke about a guy who tried to teach his mule to live without eating. He tied the poor mule to a post and gave him water, but no feed. About the time it appeared the mule was learning to live without eating, the mule died. We just can’t grow rice without feeding the plants. And we do not intend to cut back on fertilizer in our verification program.
Chlorophyll meter fits PD/later applications
DR. M.O. “Mo” WAY
As you well know, your fertility program is crucial to the success of your rice crop, which responds dramatically to N, P and K. However, fertilizer costs are skyrocketing. Randy Waligura, who provides inputs to Texas rice farmers west of Houston, informed me recently that a typical Texas rice fertility program of 180N-60P-40K will cost approximately $155/acre in 2008. For comparison, the 2007 cost for this same program was $120/acre. Dr. Larry Falconer, Texas AgriLife Extension Service Ag Economist, noted that urea will cost more than $500/ton in 2008. Although these fertilizer costs are alarming, don’t short change your fertility program to save a buck. Your goal should be to optimize your fertility program to maximize yields.
The 2008 Texas Rice Production Guidelines contain the latest information on recommended fertility programs specific for soil type, cultivar and region in the Texas Rice Belt. This publication can be accessed via http://beaumont.tamu.edu.
In general, soil testing is recommended before planting to determine P and K needs. Make sure you follow instructions for sampling and, as a precaution, prepare duplicate samples as a check on the reliability of the testing procedure. In Texas, research consistently shows that early plantings of conventional cultivars (non-hybrid) in March require a three-way split of N with 20, 50 and 30 percent applied at planting, preflood and panicle differentiation (PD), respectively. For hybrids, most of the N is applied preflood, regardless of planting date. Consult the above guidelines for more specific recommendations.
Use of a chlorophyll meter is recommended for PD and later applications. Again, refer to the 2008 Texas Rice Production Guidelines for cultivar-specific, threshold chlorophyll readings. The general color of your rice crop is highly dependent on cultivar, physical foliage characteristics, time of day, cloud cover, wind, etc. Relying only on visual observations to determine if and when your rice needs N is not recommended. I have observed in my own research plots that sometimes a PD N application is a little late. By the time rice is at PD, the crop clearly needs N (color and height of rice is not uniform). Once this occurs, the crop struggles to “catch up” due to a stress situation. To achieve maximum yields, any stress (caused by abiotic or biotic factors) must be minimized. Check your rice carefully and often for midseason N needs prior to and at PD.
Speaking of PD, I know some of you farmers may have difficulty identifying PD. A good method to learn how to identify PD is to select a typical area in one of your rice fields. Make sure the area contains uniform rice (stand, color, etc.). Carry an exacto knife or sharp pocketknife and a 16x hand lens. Soon after flood and about twice a week until heading, pull two or three rice plants from the flooded soil. Select the middle culm of each plant, and cut it at the base. Then slice the culm lengthwise from bottom to top. Inspect the inside of the culm for the developmental status of the plant. You will be able over time to see all the stages – green ring, internode elongation, PD and panicle development in the boot – using this method by tracking rice development in your field.
Also, you can access the Rice Development Advisory via the Beaumont Center Web site. Plug in the required information concerning your crop, and this program will predict when various developmental stages will occur. However, don’t rely solely on this program; you must “ground truth” the predicted information. So, “let’s get ready to rumble” for another rice season. Wishing you the best rice crop ever. Thanks to Mike Jund, research associate at the Beaumont Center, for providing some of the fertility information in this article.
Weigh the benefits against the high cost of starter fertilizers
Dr. Jim Hill
The concept behind starter fertilizers is to improve early season vigor by placing crop nutrients in the upper soil zone where the roots of germinating seedlings can get to them early. Phosphorus (P) is a relatively immobile nutrient, thus under cool conditions when root growth is slow, plants may show a deficiency even in soils with adequate P. However, early access to P may prevent this temporary deficiency. Generally, though, if soil tests show adequate P, the plant will eventually be able to take up sufficient P for good growth.
One of the biggest issues for starter P is proper soil incorporation. A recent survey shows P is not properly incorporated, if at all, in more than half of California rice fields. Research on algae, particularly on Nostoc spp, (popularly referred to as “black algae”) show that P levels in the water are well above the threshold for stimulating this weed. It is no wonder that growers are increasingly complaining about algae problems.
Phosphorus on or near the surface also stimulates the growth of many other small-seeded weeds germinating in the top half-inch of soil. It is also common to apply starter nitrogen (N) with P. In the case of starter N, fertilizer skips or side-by-side research plots often appear as though seedling vigor is visually improved by the starter. This may be particularly true where preplant banded ammoniated fertilizers are incorporated too deep. In these cases, seedlings between the bands appear N deficient until their roots spread enough to take up adequate N. Starter N, which is purposefully placed near the surface, is also much more subject to loss during field drains, so the risk of losing starter N is much greater than losses incurred by preplant N.
Despite the visual improvement of seedling vigor with the use of “starters,” there is little hard evidence to show that this early apparent vigor translates into yield improvement compared to an equal amount of N added to and all applied as a one-shot preplant incorporated program. Growers should carefully weigh the benefits of early seedling vigor against the high cost of starter fertilizers and their potential for stimulating weed and algae problems and, in the case of N, the lower efficiency that can result from N losses.
Check out updated DD50 rice program
It seems you can’t win. Higher crop prices are matched by higher input costs. Obviously, you can win, or we would have no rice farmers still in business. Here are some details to increase net income by minimizing expenses while maintaining optimum yields.
Periodic soil testing is essential. The goal is to apply enough fertilizer for optimum yields, while avoiding over fertilization and wasting of money. Though it takes effort, proper sampling is key. Take 10-plus subsamples per 20 acres. Avoid areas below levee gates.
The Missouri DD50 Rice Growth Prediction Program is another invaluable tool. Dr. Gene Stevens and a team of specialists at the Delta Research Center in Portageville have recently updated and improved the program.
An important detail in the DD50 report is the recommended nitrogen rate for each variety. The time of application is as important as the rate recommendation. The advance notice provided by the DD50 helps schedule nitrogen applications.
Herbicide options are given for early postemergence and post- flood weed control. The cutoff date for late propanil application is given as well. Insecticide choices, rates and timings are given for armyworms, stem borers, rice water weevils and stink bugs. Fungicide options are also given for sheath blight and blast control.
The farmer (or the scout) is responsible for providing an accurate date of emergence, then later in the season to verify the actual (1) beginning of tillering, (2) beginning internode elongation and (3) 50 percent heading. Field scouting is essential to identify weeds, insects, diseases and treatment thresholds. Either the farmer or a hired scout must be committed to field verification.