Do the math. With fertilizer prices still at near record highs, farmers may look at management approaches and new products that promise to increase efficiency, especially for nitrogen. But are specialty products the answer or merely costly alternatives that do little to meet plant nutrient needs? It may depend on soil needs, crop type and tillage practices, as well as moisture and other climate conditions beyond farmers’ control.

At the very least, producers should look at research into products and practices that promote improved nutrient efficiency, says a Texas Extension specialist.

Mark McFarland, Regents Fellow, professor and a Texas A&M AgriLife Extension Service soil fertility specialist, says farmers are concerned about making the most of their increasingly expensive nitrogen investment, but he cautions them to analyze costs and benefits before buying products promoted to improve nitrogen efficiency.

He points farmers to a recent study conducted throughout the South and reported byCharles Mitchell, Extension agronomist, Auburn University; and Deanna Osmond, Extension leader and professor in soil science at North Carolina State University.

That study looked at several nitrogen products applied to various crops in Alabama, Arkansas, Florida, New Mexico, Oklahoma and Texas. The study is available in the Southern Regional Cooperative Series Bulletin (http://aurora.auburn.edu/repo/bitstream/handle/123456789/44121/scsb-416.pdf?sequence=2) .  It is the first article under “News” at: http://srwqis.tamu.edu/

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The researchers said, “Minimizing nitrogen fertilizer rates while maintaining crop yields is essential both for improving agricultural profitability and reducing environmental consequences of farming, such as leaching and runoff from agricultural crop fields, which can be major sources of nitrogen to streams, rivers, and estuaries in the Southeast.”

They added that recent significant increases in nitrogen prices have sharply increased crop production costs, motivating farmers to look for alternative nitrogen sources.

“For most farmers, the only potential nitrogen alternatives (to inorganic fertilizers) include planting legumes as winter cover crops (which can deplete soil moisture needed for the primary crop) or applying animal manures (which are not available in all production areas). Another option is applying slow release nitrogen fertilizers, which have the potential to improve nitrogen use efficiency in corn and other field crops and, thereby, enhance both production economics and environmental protection.”

Traditional nitrogen sources come with challenges, the report says. “Ammonium nitrate (34-0-0) formerly was the standard but has become difficult to find and transport. Solid urea-ammonium sulfate blend (33-0-0) is very acid-forming and subject to volatilization. Solid urea (46-0-0) has a high risk of volatilization losses during hot, dry summer months when surface applications are not incorporated. This is especially true when urea is applied on crop residue in a high pH soil.

“Reduced tillage and high-residue management in row crops often require surface application of some materials. Liquid urea-ammonium nitrate solutions (UAN) are currently the most popular nitrogen source for row crops.”

Other alternatives include nitrification inhibitors (e.g., Nitrapyrin), available for many years but used mainly in the Midwest where fall-applied anhydrous ammonia is popular.

“Recently, urease inhibitors (e.g., Agrotain) have been marketed to help manage urea-based nitrogen fertilizers. Many new polymer coated products are on the market to control the release of nitrogen from both liquid and dry urea-based materials.”

Add to fertilizer costs

Using these products, however, adds to fertilizer costs. So Mitchell and Osmond ask: “Are the benefits worth the extra cost? Do these materials work effectively and consistently under the heat and humidity of the Southern U.S. and for the major crops produced in the region?”

Results vary, according to the Southern Region Water Quality Program Special Project funded through the USDA National Institute of Food and Agriculture (NIFA). That study was designed “to evaluate the effectiveness of several slow-release nitrogen fertilizers and nitrogen fertilizer stabilizer products, compared to standard nitrogen fertilizers … for selected major row crops in the cooperating southern region states: Arkansas, Alabama, Florida, New Mexico, North Carolina, Oklahoma, and Texas.”

In each state, research included alternative and new technology nitrogen sources tested independently. Trials compared these products to “traditional” nitrogen sources, using crops and management practices common to each state. “Rates, methods and timing of application(s) depended on the objectives for each experiment. Where possible, materials were applied according to the manufacturers’ recommended rate and method. However, because of the difficulty of comparing commercial products, each state used products differently.

The traditional nitrogen sources used included: ammonium nitrate, urea-ammonium sulfate, liquid urea-ammonium nitrate (UAN solution), urea, dairy manure, and poultry litter. Alternative products evaluated included: Agrotain (urease inhibitor), Nutrisphere N (urease and nitrification inhibitor), Nitamin Nfusion (a slow release nitrogen source), Environmentally Smart Nitrogen (ESN, a polymer-coated, controlled-release urea), NDemand 30L 30-0-0 (a slowly available, liquid nitrogen), CoRoN 25-0-0 (a controlled release liquid nitrogen), UCAN 23 (YaraLiva) (includes water-soluble calcium to reduce ammonia volatilization), New Suryamin (includes organic nitrogen and bio-enzymes).

Results across all the states indicate:

• Nutrisphere, Nitamin and Agrotain did not improve yields at any location for any crop tested.

• Pre-plant incorporated ESN (as compared to urea) improved the corn yield at one site in Arkansas. When tested at two sites in Arkansas, ESN improved seed cotton yield at one site but produced yields equal to urea at the second site. However, surface applied ESN performed similarly or worse than UAN solution or urea in Alabama (corn), North Carolina (corn and wheat), Oklahoma (wheat), and Texas (grain sorghum).

• Evaluation of three organic nutrient supplements on vegetables in Florida gave mixed results, depending upon the rate and method used but generally required regular fertilizer applications to maintain optimum yields.

Individual state results include:

Alabama

Alabama tests included no-till, non-irrigated cotton and corn with evaluations of ammonium nitrate, urea, urea-AS blend, UAN solution, Agrotain, Nutrisphere, Nitamin Nfusion, ESN, poultry litter and calcium chloride.

Controlled release nitrogen and nitrogen stabilizer products did not show any yield advantage compared to more conventional nitrogen sources such as urea, ammonium nitrate, UAN solution, or the urea-ammonium sulfate blend, which is being sold as a substitute for ammonium nitrate. Agrotain did not reduce ammonia losses in general but did reduce losses when both urea and UAN solutions were applied to a high residue cover.

Poultry litter results in very high ammonia losses when applied as a sidedress to both cotton and corn. For the relatively low, non-irrigated yields represented by this study, the newer, controlled-release nitrogen products failed to produce a consistent yield advantage over traditional nitrogen materials such as urea, UAN solutions, or a urea-ammonium sulfate blend.

Arkansas

In Arkansas, researchers looked at conventional-tilled, non-irrigated corn and cotton. ESN was compared to urea at five rates of application, plus no nitrogen as a control.

The 2010 summer was drier than normal, making fertilizer nitrogen losses from denitrification less likely than in wet years. Corn yields, averaged across all nitrogen rates, were numerically greater by 10 percent when ESN was applied pre-plant compared to urea applied pre-plant. Yields of cotton treated with urea and ESN were not significantly different at one site, but were significantly different at another site.

These results indicate that ESN is a suitable, alternative nitrogen fertilizer (to urea) for both crops. Use of ESN as the pre-plant nitrogen source does not necessarily guarantee greater corn and cotton yields than urea under all conditions but likely helps reduce the risk of losing greater amounts of nitrogen in wet years. ESN should be considered a tool that can enhance nitrogen management and crop uptake. Additional research, encompassing several years and various field and weather conditions common to Arkansas, is needed to determine the frequency and magnitude of yield increases and whether other crop management benefits may be realized when ESN is used in place of urea for pre-plant nitrogen applications.

Florida

Florida studies included tomatoes and bell peppers, irrigated and under plastic mulch. Research looked at three products: New Suryamin, Megacal, and BioPotash. The products did not show any effective yield or quality advantages in 2009 as nutrient requirements of both green bell peppers and tomatoes were more than adequately met through both pre-plant soil application and supplemental nitrogen fertigation. However, in 2011, as the treatment combinations were changed appropriately to document the effects, yields and performance in both crops were significantly lower in absolute control and with product sprays alone indicating the need for regular fertilizer applications.

In tomatoes, application of the product spray resulted in significant yield increases over both absolute control and the standard recommendations, indicating that under intensive nutrient management practices foliar spray may help tide over nutrient stresses, particularly with regard to highly leachable and mobile nutrients such as nitrogen and potassium.

A 25 percent savings in fertilizers was realized without yield reductions when fertilizer was applied at standard recommendations in combination with the product spray. In green bell peppers, a 25 percent savings in fertilizer was possibly derived by the 75 percent SRP and 25 percent product spray combinations.

Also, the granular and foliar spray combination at 50 percent dosages produced significantly higher yields, suggesting that if the dosages of the product combinations of soil and foliar applications were increased to 100 percent, the potential is to increase yields or to achieve the highest yields. Foliar applications of nitrogen and potassium products at 100 percent labeled dosages could sustain the supply to meet all the crop nutrient requirements.

New Mexico

In New Mexico, tests evaluated urea, UAN, Agrotain, and dairy manure on corn and irrigated cotton.

There was no effect of nitrogen source or timing on fresh weight of corn. Dry matter yield was similar to applying 11-52-0 only, suggesting that nitrogen was not sufficiently mineralized from the manure application in time to contribute to yield. Crude protein content was lower in the corn plant from both manure application rates compared to UAN and urea treatments.

Estimated milk production on a per acre basis tended to be greatest from corn treated with one application of UAN, urea, or urea treated with Agrotain over two applications (greatest numerical yield). Applying manure at an application rate that estimates 35 percent mineralization may have contributed excessive salt to the soil and decreased plant dry matter accumulation. Fertilization of cotton had no impact on cotton yield. The nitrogen sources used had no impact on cotton yield or fiber quality.

North Carolina

Wheat and corn production tests in North Carolina included UAN solution, Nitamin (UFP), ESN, and Nutrisphere at various rates.

The wheat data suggest that UAN, NutriSphere, and UCAN produced similar grain yields for all four site years. The ESN yields were lower than the other fertilizers for one site year. The use of ESN for wheat straw production is not recommended as it produced lower yields 75 percent of the site years. The use of any of the alternative nitrogen fertilizer products over UAN for wheat grain production would be heavily influenced by fertilizer pricing.

Over the six site years of corn grain yield data, five demonstrated no agronomic advantage of the alternative fertilizer products over UAN for grain production. In the one site year, UAN produced less grain than the alternative fertilizer products; this may have been due to a change in tillage system. In three of the six site years, NutriSphere and ESN produced higher corn stover yields than UAN. Two of those years were in the mountains, suggesting that NutriSphere may offer an agronomic advantage over UAN in the production of corn stover in the mountains under the field conditions in this study.

A separate incubation study demonstrated that UCAN and NutriSphere released nitrogen on a time scale similar to UAN under the laboratory conditions. The release time for ESN in the five soils was approximately 7 to 42 days and was slower than UAN, NutriSphere, or UCAN.

Overall, the use of these alternative nitrogen fertilizers in North Carolina provides little agronomic benefit to corn or wheat grain production. Producers who use the products for stover or straw production should be aware of cost differences between products.

Oklahoma

A two-year study in Oklahoma (2010 and 2011) tested urea, Nutrisphere-N, Agrotain, and ESN in winter wheat.

Across both location and years there was no significant difference in wheat grain yield, protein, or residual soil nitrate levels when a product or additive was added and compared to urea at the same nitrogen rate. Regardless of tillage practice, there was no benefit in terms of yield or nitrogen concentration of using a slow release nitrogen source or a nitrogen stabilizer product.

Texas

Studies conducted in 2010 in Texas evaluated UAN, Nutrisphere-N, Agrotain Ultra, N-Sure, NDemand, and CoRon. Crops included corn, cotton, and grain sorghum.

For corn, there wereno differences in grain yield or test weight between the control and treatments receiving UAN, UAN with urease-nitrification inhibitors, or UAN blended with any of the three slow-release nitrogen products.  Likewise, there were no differences in cotton lint yield, gin turnout or fiber quality parameters between the control and any of the treatments, including various rates of nitrogen fertilizer using UAN, UAN with urease-nitrification inhibitors, or UAN blended with any one of three slow-release nitrogen products.  

Grain sorghum yield responded to increasing rates of coulter-banded UAN fertilizer applied at the second leaf stage. However, nitrogen stabilizers and slow release products surface dribble- banded at 30 and 60 pounds of nitrogen per acre did not improve grain sorghum yields compared to conventional UAN or urea at equal rates.

“Overall, this research indicates that crop response to the nitrogen stabilizer and slow release products evaluated was variable,” McFarland said. “While some of the products did show positive benefits, the results were not consistent across the different crops, sites, or years tested..”

He said environmental conditions in a given cropping season, particularly temperature and rainfall, along with soil type, are key factors in determining whether a nitrogen stabilizer or slow release product will protect nitrogen from loss and potentially improve crop response.

“Given the high cost of nitrogen and the environmental consequences of losses into surface water and groundwater resources, nitrogen fertilizers must be managed very carefully,” he added. “In the case of nitrogen stabilizers and slow release products, more research is needed to document precisely if, when, and where a specific product can help agricultural producers do that consistently and economically.”

 

 

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