Fertilizer timing is critical for economic returns on your farming. I’ll never forget a study conducted by Dr. Dale Blevins at the University of Missouri back in the late 1980s. Dale was able to obtain tremendous yield increases by delivering nutrients directly into soybean plants via medical intravenous setups. Obviously, using an IV to deliver nutrients is not practical, but it does demonstrate the value of a constant nutrient flow throughout the growing season.
Nitrogen receives the most application timing attention. This is because of its soil mobility. In almost all cropping situations, it is agronomically efficient to split nitrogen applications. In many situations, that translates into improved economic efficiencies.
Although many producers do quite well with all of their corn nitrogen applied preplant, I am a supporter of splitting corn nitrogen applications as a key management practice for producing consistently high yields.
Unless your environment allows for fall/winter anhydrous application, I usually recommend some nitrogen (a quarter to a third of the total crop needs) at or near planting, followed by the remaining nitrogen applied sidedress at the three- to six-leaf stage. This strategy provides the seedling adequate nitrogen. It also provides the growing crop with a dependable nitrogen supply immediately prior to the rapid growth that occurs between the six-leaf stage and tasseling. It also allows for mid-season rate adjustments based upon within-season environmental factors.
In wheat, I recommend two or three-way nitrogen splits. Some nitrogen (about a third) is needed at or near planting to stimulate fall tiller production.
The remaining nitrogen should be applied just prior to spring green-up. In planned high yielding programs (greater than 100 bushels per acre), the non-fall nitrogen can be split into two spring applications, with half near green-up and the other half near the boot stage.
Nitrogen use and timing for soybeans is often debated. Some preplant (10 to 20 pounds per acre), usually applied through nitrogen-containing phosphorus materials, can aid the seedling’s development prior to nodulation. Recent work has also shown that, under high yielding conditions (greater than 60 bushels per acre), 10 to 20 pounds of nitrogen per acre applied near pod set can help “finish off” a crop.
Tall fescue benefits from split nitrogen applications. In grazing situations, I prefer the majority of tall fescue’s nitrogen applied in late August to stimulate winter stockpile production. In hay situations, I prefer the majority of the nitrogen applied near spring green-up. In combination situations (hay + stockpile) a 60/40, spring/fall split application works well. When moisture conditions are appropriate, an additional nitrogen application in the early summer after haying or aggressive spring grazing pays great dividends.
Proper fertilizer timings do not only apply to mobile nutrients like nitrogen. Relatively non-mobile nutrients like phosphorus and potassium are commonly applied based upon convenience, and often applied once every other year. Although this timing philosophy works well in many situations, sometimes more frequent applications are beneficial.
High or low pH soils have the ability to fix or tie-up phosphorus. Some types of soil clays have the ability to fix potassium. In most cases, moving from a biennial to an annual fertilization system will help eliminate tie-up issues.
Certain crops (especially forages) have the ability to take up and remove via harvest more phosphorus and potassium than they require—a term referred to as luxury consumption. For this reason, in alfalfa, we generally recommend half of the annual fertilizer after the first cutting and the other half after the third cutting.
Environmental inconsistencies with the timing, release and availability of crop nutrients, along with higher commodity values have increased interest in slow-release materials, fertilizer enhancers, fertilizer protection products and bio-stimulants.
Some of these materials, like Super U, ESN, Agrotain, N-Serve and NFusion for nitrogen, and Avail for phosphorus, have been tested and can reduce the need for multiple applications in some situations. Other lesser-known and less researched materials may or may not help. Some have very little merit and should be avoided. Sorting through all the claims concerning untested products is a difficult task. My advice is to always stick with products that have been evaluated by unbiased, trusted parties.
Dr. Paul Tracy is director of agronomy for MFA Incorporated.
When asked if urea is superior to ammonium nitrate, I usually respond with one of three words—yes, no or maybe. Last issue, I mentioned the 4 Rs of crop nutrition currently being promoted by the plant food industry. The Right source at the Right rate, Right time and Right place. Although the four are completely interconnected, let’s discuss the right source. I’ll use common nitrogen sources as a brief example. Other nutrients have similar but unique discussions of their own. All major nitrogen materials can be effective, if used in a wise and material-specific manner.
Anhydrous ammonia contains the highest nitrogen analysis available (82 percent). It is consistently the lowest cost nitrogen fertilizer in our system. Anhydrous turns gaseous at atmospheric pressure and must be incorporated into the soil to avoid volatile losses. Application on rocky, cloddy, or excessively dry/wet soils may induce volatility. The obvious rule of thumb is that if you can see it or smell it, adjust your equipment or wait until better application conditions exist.
When applied properly, anhydrous is extremely efficient. It converts to plant-available ammonium rapidly upon contact with the soil. Its incorporation requirement advantageously places it in the root zone near crop roots. For a few weeks post application, anhydrous reduces soil bacterial populations responsible for nitrification. It therefore provides some “stabilization” properties which can lower potential nitrate losses.
Depending upon crop and weather conditions, anhydrous ammonia can be applied in the fall, spring or at sidedress during the growing season. The nitrification inhibitor N-Serve (Nitrapyrin) is a wise choice to delay fall and early spring applied anhydrous ammonia from nitrifying.
At 46 percent nitrogen, urea is the highest analysis dry nitrogen fertilizer available. This generally lowers its cost compared to other dry nitrogen fertilizers. Urea must be converted to ammonium before becoming available to plants. Some urea naysayers feel that a delay in ammonification makes urea an inferior fertilizer product. In reality, urease, the enzyme responsible
for converting urea to ammonium is one of the most common enzymes present throughout nature. Our soils and crop residues easily supply enough urease to rapidly convert urea to ammonium within a few days of application.
Urea’s biggest negative is that during the urease hydrolysis process, gaseous ammonia forms, making volatility losses possible. In cool weather (reduced urease activity) or when rainfall/irrigation moves urea below the soil surface, volatility becomes minimal. Under high urea volatility conditions (70+ degree temperatures, wet-drying soils and heavy surface residue), urea can be protected using the urease inhibitor Agrotain.
Unlike urea, ammonium nitrate contains nitrogen in the two forms that are immediately plant-available. It is also not subject to volatility losses. Since it is only 34 percent nitrogen, it is generally higher priced than urea. Under high rainfall/soil saturation conditions, the nitrate component of ammonium nitrate can be lost immediately via leaching or denitrification. I generally use this as a counter balance to the negatives associated with urea. Like most cropping decisions, the environment dictates which nitrogen material will perform best.
Urea ammonium nitrate (UAN)
UAN generally contains 28 or 32 percent nitrogen. It is a liquid material made from mixing urea, ammonium nitrate and water. Therefore, it possesses the strengths and weaknesses of both materials. Being a liquid, it fits weed-and-feed programs. Liquids also work well with knife delivery, especially during sidedress application. Some producers believe rate calibration and delivery accuracy are superior with liquid materials.
However, liquid materials do have a few negatives. You are transporting a lot of water, which often increases the cost per unit of nitrogen. In no-till or heavy surface residue situations, broadcast liquid
nitrogen materials can get captured and “tied-up” by residue before reaching the soil.
Ammonium sulfates/ ammonium phosphates
Ammonium sulfate, diammonium phosphate (DAP), mono ammonium phosphate (MAP), and the ammonium polyphosphates all provide plant-available nitrogen. Since they contain relatively low nitrogen contents (11 to 21 percent), their cost per pound of nitrogen can be limiting. Therefore, we recommend using them to meet crop phosphorus or sulfur needs. In most cases we credit the nitrogen in these materials toward the total crop need and supply the majority of the nitrogen through one of the higher analysis fertilizers.
When selecting a fertilizer material, consider their physical and chemical properties, combined with environmental
conditions present and the other 3 Rs. Visit your MFA Certified Crop Adviser to help evaluate which nitrogen material fits each field, each year, within your farming operation.
Paul Tracy is Director of Agronomy for MFA Incorporated.
This year’s wet weather and delays will affect 2010 on your farm
Once again it’s December, and I’ll discuss a few observations from the past year. It provides an opportunity to point out some “learning experiences” and prognosticate how these issues will affect our lives over next 12 months.
Obviously, this field season was dominated by WET weather. As I write this in late October, Columbia, Mo., has received close to 50 inches of rainfall this year. Delayed harvest, grain quality and delayed fall fertilization are primary concerns. Hopefully by press time, things have gotten better, the crop is out and we are already preparing for next season.
Over the next few years, you’ll be hearing a lot about the four Rs of crop nutrient management. The International Plant Nutrition Institute developed the program based upon promoting the Right source, Right rate, Right time, Right-place strategy of managing crop nutrient inputs. Realistically, agronomists have always practiced the 4Rs. In 2009, many of our fields lost applied nitrogen because of excessive rainfall. The 4R philosophy helped prevent some of that loss.
After several years of international marketing, transportation logistics, commodity brokering and other non-production components of crop nutrition, it is nice to see the industry concentrate on agronomics. We at MFA have never strayed from that core mission. In February, I’ll start a series on the 4Rs.
Once again, the power of modern crop genetics amazed this year. Both soybeans and corn were planted into poor conditions last spring. They responded quite nicely, with good growth and yield.
However, this does not mean that one size fits all. New traits and technologies need to be evaluated based upon local environments. Many poor choices are made when local decisions are directed by national programs or trends.
MFA Incorporated spends appreciable time, effort and resources evaluating genetics at the local level. We do this to ensure that our growers have the best opportunity for success. If you have not already done so, get with your MFA seed specialist and/or Certified Crop Adviser to make the right choices for 2010.
The 2009 season reminded us not to put all of our genetics in one basket. Some high yielding lines did poorly under extremely wet conditions. Some genetics designed to hold up well under drought stress conditions did not yield as well as their high-yielding counterparts. No one can predict next season’s conditions. Therefore, please consider a strategic minimum-risk approach to seed selection. This includes selecting genetics based upon local history, soil conditions, crop nutrition, field drainage and other related factors.
The wet fall and relatively low wheat grain price has left us with a tremendously small amount of winter wheat acreage. This should stimulate more full-season soybeans next year. When planting soybeans early, consider residual herbicides, seed treatment, proper fertilization and appropriate maturity groups.
For the second straight season, heavy forage production and large amounts of hay removal have further depleted our forage-crop soil fertility levels. A large majority of soil samples coming from forage fields this fall are showing low phosphorus and potassium levels. Fertilizer prices have stabilized, making now a very good time to replenish those nutrients.
The past two years have provided excellent germination, growth and tonnage of forage legumes. One thing made very clear this year was that when soils were deficient in nutrients and/or low in pH, they produced only a fraction of the legumes present in neighboring well maintained fields.
MFA’s Agronomy Services division has continued to help producers write and maintain nutrient management plans. As we get nearer to the 2011 deadline for plan development, this activity is expected to increase. I recommend that all row crop and livestock producers develop plans (regardless of mandated requirements or state/federal subsidies)..
Similar to nutrient management plans, you’ll see us increase integrated crop management activities like crop scouting and crop consulting. MFA is positioned to offer these services.
The 2009 season marked the fifth straight year of increased precision agriculture programs (sales and services) for MFA Incorporated. During that time we have clearly demonstrated ourselves to be the leader in bringing this technology to the region. Our comprehensive programs offer the most complete package in the marketplace. We offer service for equipment, grid sampling, zone sampling, variable rate seed and fertilizer technology, RTK accuracy. And we couple those services with co-dependent input selections like seed, fertilizer and crop protection products.
Overall, the 2009 field season was turbulent, but resulted in good agronomic production.
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