- Specialists Speaking -
Dr. Nathan Buehring
The high cost of fuel and fertilizer in 2008 led producers to being more efficient with water and fertilizer. Mississippi producers purchased and laid more polypipe than ever in rice last year. As always, economics was the driving factor for being more efficient. Producers who used multiple-inlet irrigation finally realized there are other benefits than just reducing their fuel bill, such as better nitrogen efficiency, reduction in cold water areas and better overall water management.
The cost of urea has recently come down, but it is still expensive. Being very efficient with nitrogen is going to be a key for maximizing the highest return on high-priced urea. Multiple-inlet irrigation helps establish the flood quickly, which is essential for getting the most nitrogen available to the plant. A long period between the nitrogen application and flooding will lead to nitrogen loss, especially without Agrotain-treated urea.
Using Agrotain-treated urea will help minimize nitrogen loss up to 10 days after application.
Mississippi’s nitrogen recommendations have not changed from previous years. We still recommend a total of 180 lb N/A for clay soils and 165 lb N/A for silt loam soils. For semi-dwarf varieties (CL 131, CL 151, CL 171-AR, Cocodrie and Sabine) grown on clay soils, we recommend 120 to 150 lb N/A applied preflood and then followed with 30 to 60 lb N/A at mid-season. For varieties that are susceptible to lodging (CL 161 and Wells) on clay soils, decrease the nitrogen rate to 90 to 120 lb N/A at preflood, followed by the remaining at mid-season 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 mid-season for semi-dwarf varieties and 90 lb N/A at preflood and 60 lb N/A at mid-season for CL 161 and Wells.
We have also seen issues with phosphorus in the Mississippi Delta. The price of diammonium phosphate (DAP) has subsided from its high in 2008 and is currently being sold for about $500/ton. While that amount is still rather high, phosphorus will be needed on some soils that are deficient.
Soil sampling will be the best asset in determining whether or not phosphorus or any other nutrient is needed in a fertility program. If the soil test results for phosphorus fall into the medium category, I would suggest starting to add phosphorus into a fertility program. A blend of 50 lb/A of ammonium sulfate and 50 lb/A of DAP applied at the one- to two-leaf stage is a good option to start adding some phosphorus back into the soil as well as supply early season nitrogen for improved vegetative growth.
Where phosphorus deficiency is a serious problem, DAP at 100 lb/A will be needed to correct the deficiency. If you still haven’t soil sampled, I would recommend soil sampling this spring before planting season begins. This practice is the most valuable tool in making sound agronomic and economical fertilizer recommendations.
Don’t decrease rates
Dr. John Saichuk
At one of our winter meetings in a conversation with a grower we both agreed, “Farming is never boring.” Certainly, we can always expect an unplanned challenge and must be prepared to adjust. Once in my career I would like to experience a year with no major challenges. I guess I am just getting lazy.
It would seem we have addressed all of the topics we could about rice fertilization. Last year Dr. Harrell was frequently asked if growers could decrease fertilization rates (especially nitrogen) because of the exorbitant increases in their prices. Following is one example that is representative of all varieties he evaluated.
Using a price of $.52 per pound of nitrogen (about $475 per ton of urea) and a selling price of rice of $14 per hundredweight, the optimum nitrogen fertilization rate was 172 pounds of nitrogen (374 pounds of urea) per acre. When he changed the price of nitrogen to $.87 per pound of N (about $800 per ton of urea) and the selling price of rice to $10 per cwt, the optimum fertilization rate changed to 162 pounds of nitrogen (about 350 pounds of urea) per acre. The answer to the initial question is, “Not really.”
Over the years, the farmers I have seen get into trouble were those who tried to “put in a cheap crop.” In most cases, their yields slowly eroded and along with them their profitability. In one of our veri-fication trials several years ago, the grower thought we were asking him to spend too much money. We decided to split the field. In the end, we did spend more money, but we also produced more rice and more gross returns.
The net returns did not appear to be significant until we looked at them on a whole-farm basis. If his farm had been 1,000 acres, the difference would have been another $20,000 in his pocket.
From our verification program experiences, we have consistently gotten the best use of nitrogen when we can apply about 2/3 of the total at or just prior to establishing a permanent flood. The remainder, we apply at mid-season.
Theoretically, we could apply all of the nitrogen at once, but by splitting the application we are able to adjust the rate at mid-season. If we have reason to believe we may have lost nitrogen and have good yield potential, we may add more nitrogen than we had initially planned for in the second application. More than two applications are seldom of use unless nitrogen has been lost.
In some dry planted fields we apply a small amount of nitrogen fertilizer ahead of a flush. In this case, we seldom see a yield benefit, but we benefit by getting the crop up and going and are able to apply herbicides early and establish a permanent flood sooner. Last year we saw many fields that were not flooded until internode elongation (green ring) or nearly so. This often penalized the crop by sacrificing weed control, delaying maturity, increasing disease and reducing yield.
After 11 years and 4,500 acres in over 100 rice research verification fields throughout the state, it is abundantly clear the highest rice yields occur where we establish permanent flood as early as possible and keep it in place as long as we can. Our varieties perform better that way.
Consider P & K
Dr. M.O. “MO” WAY
As you well know, proper rice plant nutrition is absolutely essential to producing a successful crop. In light of booming prices for fertilizer, nutrient management takes on increasing importance in your production program. At the time of writing this article, urea in southeast Texas was selling for about $440/ton while 18-46-0 was going for about $600/ton and 0-0-60 was selling for a whopping $875/ton.
For instance, 20 units of K costs about $14/acre, so if you don’t need K, why apply it? This shows you the importance of taking soil samples NOW to determine the need for P and K. In many cases, you may not need P and K, but by all means, if your samples indicate a deficiency, apply the proper amounts of P and/or K. And, as always, consult your state Extension service/experiment station folks for specific recommendations.
We know N is expensive, but don’t cut back on your N if your crop is deficient. Follow the general recommended guidelines and modify according to the specific needs of your crop. For early planting of non-hybrid rice varieties in Texas, a three-way split (at planting, preflood and PD) is recommended, but if your crop is beginning to lose uniformity in height and color before PD, apply N at this time. This means checking your crop often and carefully for N deficiency. At the same time, you can spot other problems, such as diseases, insects and weeds. So, scout, scout and scout some more!
Recent research conducted by Lee Tarpley at Beaumont and Tim Walker in Mississippi has shown nice hybrid yield responses to increased N applied to heavy clay soils. As you know, increased N can lead to lodging in hybrids, but these yield responses are dramatic. Follow the basic recommendations outlined by RiceTec, but I also encourage you to discuss this issue with your RiceTec representative and experiment station/Extension service colleagues.
Make efficient use of the N you apply. This will help your crop and pocketbook. The best possible scenario is to apply a flush or flood as soon as possible after your N application. Under aerobic conditions, your applied N will be lost to the atmosphere or leached away from your crop’s roots. For your ratoon crop, a single application of N on dry soil just prior to flood has been shown to be most efficient. The standard recommended application rate is 100 lb N/acre, but adjust upwards if you have a good ratoon crop yield potential. You may want to apply 120-130 lb N/acre, especially if growing a hybrid variety.
I recently attended the Cotton and Rice Conservation Tillage Conference in Marksville, La. A lot of really good plant nutrition information was passed along at this conference. I encourage you to attend this annual meeting. If you want more info, please contact me at (409) 658-7394 or firstname.lastname@example.org.
Researchers and farmers team up and discuss rice production issues related to conservation tillage. I was teamed up with a young rice farmer, Ross Hebert, from Abbeville, La. Ross applies chicken litter preplant to his entire field, but more in areas where he has cut the ground for leveling. So, chicken litter is another nutrient source especially useful in reclaiming cut ground. If you want more info on this topic, contact me, and again I can give you contact info for experts and farmers knowledgeable about chicken litter as a nutrient source.
Finally, many rice farmers in southeast Texas suffered from the storm surge associated with Hurricane Ike. Some rice fields in southern Chambers and Jefferson Counties were under salt water for days. The salt concentration in the soil of many of these fields is very high.
Unfortunately, southeast Texas has received minimal rainfall since Ike, and plentiful precipitation is the best way to reclaim these soils. For farmers in this area who have not checked their soils and water sources for salt concentration, please do so asap. Contact your county Extension agent for info on taking these soil and water samples.
I thank Lee Tarpley and Mike Jund from the Texas AgriLife Research and Extension Center and Toni Spencer from M&J Ferti-lizer for help in preparing this article.
Control ‘Black Algae’
DR. JIM HILL
Over the past few years, so-called “Black Algae” has often been a nightmare for rice growers in California. It is known more properly as Nostoc spongiaeforme. Unlike the green algae, Nostoc is poorly controlled by copper sulfate because of its gelatinous coat that won’t allow the copper to penetrate.
Dr. David Spencer of USDA has been looking at causes and potential new control methods. While he has not yet found a substitute for copper sulfate, his findings are extremely interesting because they show a strong effect of phosphate (P) fertilization practices on Nostoc. In a survey of over 60 fields, nearly half had P levels well above the threshold needed to stimulate algae growth.
These results also indicated that if P levels were at or below 0.043 mg L-1, Nostoc was unlikely to be a problem. But in cases where P was not properly incorporated, levels of P were as much as four times higher than needed to stimulate Nostoc growth. Dr. Spencer and his colleagues have recently evaluated four application methods: 1) P applied 30 days after flooding; 2) surface applied liquid P followed by a roller; 3) spring incorporated P; and 4) P applied in the fall.
Delaying P fertilizer for 30 days after flooding had much lower levels of P in the field water and reduced algal biomass by about 80 percent with no difference in rice yield. Although more work needs to be done, it is clear at least that good P incorporation or delayed P application is essential to limiting “Black Algae.”
The standard recommendation in Missouri has been to lime acid soils before soybeans but never right before rice. Zinc and boron become less available as soil pH increases. If too much lime is applied, zinc deficiency can cause rice seedlings to become sick or die when the flood is applied at first tiller.
In a rice/soybean rotation, we generally focus on the lime benefits to soybeans rather than the rice crop.
New field research is showing that liming can help rice as well as soybeans.
In field tests at Qulin, Mo., lime boosted rice yields nine bushels per acre the first year and 14 bushels per acre the second year without adding any P or K fertilizer. Some plots had lime applied right before rice (first year). Other plots had lime before soybeans and rice planted the second year.
Rice yields climbed even higher with P and K, but the economics actually favored lime alone using the high fertilizer costs in 2008. Surprisingly, Bootheel farmers have had fairly stable lime prices throughout the commodity fluctuations. Lime is about $25 per ton spread.
For rice production, do not exceed the lime rate listed in the soil test recommendation. As a safeguard for rice, apply zinc and boron. A single 10-pound application should be good for three years. Zinc seed treatments are good for supplying the crop this year but do little to build up soil levels.
Foliar zinc fertilizers are expensive and should only be used as rescue treatments. Boron deficiencies are rarely seen in rice, but Missouri studies have shown that adding boron could increase rice yields. Given the low cost of boron fertilizers and the high per-bushel value of rice, it is a good practice to mix 1/2 pound actual boron per acre in your pre-flood nitrogen.