Posts Tagged ‘small grain nutrition’

For First Split Nitrogen Applications on Wheat, Is Price per Pound of N the Right Criteria to Use?

Friday, March 2nd, 2012

Richard Taylor, Extension Agronomist;

There’s a debate going on as to what the best source of nitrogen (N) is for broadcasting over winter wheat or barley at this time of year. The question arises because it is known that urea can volatilize to ammonia (NH3), a gas, and be lost to the atmosphere because the enzyme urease, which helps break down urea, is present in all organic matter. What a lot of people overlook is the speed of this conversion which is affected by the soil pH, soil and air temperature, and moisture conditions. When temperatures are relatively low, below 70°F, and soil temperatures remain well below 50º, the activity of the enzyme is significantly reduced. Another factor involved is soil acidity or pH. When the soil surrounding the urea particle is acidic (pH<7.0), there are available hydrogen ions (H+) that can quickly react with ammonia to form an ammonium ion (NH4+). An ammonium ion is a cation that can occupy a place on the cation exchange sites in clay and soil organic matter and be held for plant absorption. The conversion of urea into ammonium bicarbonate and a hydroxyl (OH-) and then into ammonia (or an ammonium ion if an H+ is available), carbon dioxide, and water raises the localize soil pH and increases the likelihood that some of the N will volatilize off as ammonia.

In general, we found in the Deep South that you more economically apply urea to pastures or wheat fields in the early spring and often into mid-spring with only minor losses of N as ammonia. Since the soil temperature in Delaware soils seldom reaches the 50º F. level until well into April and we often have long periods of cool rainy weather in the spring, the choice of fertilizer to use on small grains is most likely best decided by economics rather than concern over just how much might be lost through volatilization. The most likely choices of fertilizer products are a urea ammonium nitrate solution (UAN) and granular urea. Since UAN does contain half urea and half ammonium nitrate, the small percentage N loss from ammonia volatilization is not likely to impact the economics between the two fertilizers very much. Growers should evaluate available fertilizers and choose the most economic fertilizer based on the cost per pound of N plus the expected application cost and the availability of the fertilizer through their usual dealer rather than arbitrarily sticking with what they’ve used in the past or what their dealer prefers to sell them.

First Split Nitrogen Application to Small Grain

Friday, March 2nd, 2012

Richard Taylor, Extension Agronomist;

Many wheat and barley fields that were not fertilized with manure or poultry litter last fall have looked poor for much of the winter. Even those fields that received some fall nitrogen (N) fertilizer but as commercial fertilizer have been yellow since mid-winter or earlier. Recently, the date when spring fertilizer can be applied was moved to earlier in February to help those with wheat that was showing signs of N stress and was trying to start spring growth. Since then, some cooler weather has settled over the region and slowed greenup in small grains.

For those who have not yet applied the first shot of N to their wheat, it is time to apply it. In fields that did receive fall manure or litter, the need is not as critical. In wheat, we have often seen about a 5 to 7 bu/acre yield increase when N applications are split into early greenup and then just before or at Feekes growth stage 5 when the first node is visible or can be felt above the soil surface. In work that Bob Uniatowski and I conducted a number of years ago, this response to splitting N applications was fairly consistent across locations and years. The largest response to a split application comes when significant rainfall occurs between the two splits causing some of the applied N to be loss either through leaching or denitrification. We also found that if all N was applied at one time, the early application date was the best choice although if the wheat had adequate tiller numbers in early spring even a Feekes growth stage 5 single application could produce excellent yield potential.

For those who may be growing barley, we did find that this crop is very sensitive to the rate of N applied because the straw strength seemed to be most affected at high rates of N. Whenever we applied much more than about 80 pounds of N per acre, we started seeding significant lodging which can not only make harvest difficult but can cause yield reductions, especially when lodging occurs early in the grain fill period.

Barley With Multiple Nutrient Deficiencies

Friday, April 22nd, 2011

Richard Taylor, Extension Agronomist; and Phillip Sylvester, Kent Co., Ag Agent;

Another field of barley with severe deficiency symptoms showed up in Kent County this past week. Although the field had received ammonium sulfate this spring, the rate used provided only about 10 to 15 lbs of S per acre, which is less than the crop requirement. If the low S fertilization rate is coupled with the heavy rainfall many areas have experienced over the past several weeks, it would not be surprising that a significant amount of the sulfate-S has leached below the rooting zone of barley. In this case, although the visual symptoms (Photo 1 and 2) suggested sulfur (S) deficiency with general chlorosis of the leaves, especially the newest leaves, and shortened plants, the soil test suggested that S was not the only deficiency likely to impact barley yield even if sulfur were added (Table 1). On the bad sample note the low soil organic matter (SOM) level (0.9%) and the impact on the cation exchange capacity (CEC) of the soil (2.1 meq/100 grams of soil in the bad area versus 3.6 meq/100 grams of soil in the good area). The CEC impact was also evident in the amount of potassium (K) and magnesium (Mg) that the soil could hold.

Photo 1. Close-up of deficient barley plants showing general chlorosis, especially in newest leaves, and stunting.

Photo 2. Field view of deficient barley plants showing general chlorosis and stunting compared with less affected plants in the background.

The short term solution to the problem is the addition of K-Mag (0-0-22-11Mg-22S) fertilizer to the field. However, the soil test results suggest that on a longer-term horizon, the critical need of the field is the addition of organic matter, either as green manure crops, compost additions, or manure additions. Trying to maximize the amount of crop residue and minimize the amount of SOM mineralization due to tillage operations is also recommended. The use of winter cover crops and green manure crops whenever the field is not being cropped will gradually raise the SOM levels, as will any additions of manures or composts. Not only with organic will additions help raise the CEC and soil nutrient holding capacity but will also help increase water holding capacity and improve yields in the long run.

Table 1. Soil test report on barley field comparing good and bad areas.

Good Barley Bad Barley
Soil pH 1:1 6 6.3
Buffer pH 6.9 7
Organic Matter % 2.4 0.9
U of D P Sat Ratio 39 59
Mehlich3 Phosphorus ppmP/FIV 193 144
K ppm 98 54
Ca ppm 442 275
Mg ppm 74 44
SO4-S ppm 20 7
Zn ppm 4.56 2.99
Mn ppm 61 15
B ppm 0.36 0.16
CEC meq/100g 3.6 2.1
H* 15 10
K* 7 7
Ca* 61 65
Mg* 17 18
Na* 0 0

*Indicated Base Saturation


Manganese Deficiency Can Worsen with Spring N Applications on Small Grains – Part 2

Thursday, April 14th, 2011

Richard Taylor, Extension Agronomist; and Phillip Sylvester, Kent Co., Ag Agent;

Last week, we discussed the possibility that either the starter fertilizer or knifed in nitrogen solution from the previous year’s corn crop might be responsible for the row-like pattern to manganese (Mn) deficiency that we had observed in barley recently fertilized with broadcast nitrogen (N). We took soil tests within the rows where barley was alive and vigorously growing (good area) and between the rows where barley plants were dead or growing very poorly (Photo 1). The soil samples have been analyzed and support our original conclusion (Table 1).



Table 1. Soil test analyses of good and bad barley areas in field showing barley surviving on 30-inch row spacing.

Barley Area Sampled

Sample Depth (inches)
0 to 4 4 to 8 8 to 12
Water pH Mn lb/A Zinc lb/A Water pH Mn lb/A Zinc lb/A Water pH Mn lb/A Zinc lb/A
Bad barley 6.1 15.1 8.5 6.6 9.0* 2.9 6.6 5.0* 1.0*
Good barley 6.2 16.3 8.7 6.3 10.8 3.2 6.5 6.3* 1.3*

*Deficient soil test level

Photo 1. Barley rows generated following renewed spring growth and nitrogen application showing effect of last year’s fertilizer (either starter band or knifed in nitrogen solution). Barley between corn rows was either severely Mn deficient or had died while barley on rows 30 inches apart grew vigorously.

Another interesting factor showed up on the soil test results. While the visual symptoms resembled traditional Mn deficiency on barley, the soil test indicated that at the deepest (8 to 12 inch) sampled layer zinc was also deficient. For any crop planted after barley (soybeans by tradition), the grower should conduct a tissue analysis mid-season before the crop begins to bloom to determine if tissue zinc levels indicate the possibility of a hidden zinc deficiency that could reduce yield potential. In addition, the grower should scout the crop for obvious zinc and Mn deficiency symptoms so that foliar zinc or Mn can be applied as early as possible.

Zinc deficiency symptoms on soybean include the following:
· Soybean yields are considerably decreased in zinc deficient soils.

  • · Deficient plants have stunted stems and leaves with chlorotic interveinal areas.
  • · Later on the entire leaves turns yellow or light green.
  • · Lower leaves may turn brown or grey and may drop early.
  • · Few flowers are formed and the pods that are formed are abnormal and slow in maturity.

Manganese deficiency symptoms on soybean include the following:
· Manganese deficiency commonly occurs in plants in well drained, neutral and alkaline soils.

  • · Interveinal areas become light green to white and the veins remain green.
  • · Necrotic brown spots develop as the deficiency becomes more severe.
  • · The leaves drop prematurely.
  • · Soybean yields can be significantly reduced by Mn deficiency.

Both micronutrient deficiencies can be reduced or eliminated by either a soil application of the sulfate or oxide compound of the micronutrient at 15 to 25 lbs per acre or by a foliar application of either the chelated form of the micronutrient or the sulfate form of the micronutrient at 1 to 2 lb of the nutrient per acre.


Manganese Deficiency Can Worsen with Spring N Applications on Small Grains

Friday, April 8th, 2011

Richard Taylor, Extension Agronomist; and Phillip Sylvester, Kent Co., Ag Agent;

Over the years, with respect to soil pH and manganese (Mn) deficiency, we have found that barley seems to be if not the most sensitive then close to the most sensitive small grain. When soil pH approaches the mid 6 range where we would expect it to be optimum for corn and beans, we often see Mn deficiency symptoms on barley, especially in certain areas of the state where the native Mn levels are low. During late fall and winter, the symptoms can often be confused with winter injury, wind burn, or other problems. However, the confusion usually clears after nitrogen (N) fertilizer is applied in the spring. Unfortunately, clearing the confusion often means that partial or entire stands of barley are lost.

The impact of spring N can vary depending on the soil acidity profile. If the Mn deficiency is severe or if the deeper soil layers are higher in pH, the N applied can cause barley plants to quickly die or, as frequently described, the barley appears to go backwards in appearance. The N stimulates rapid growth and if Mn is not available either as a result of soil pH levels or just low native Mn levels in the soil, the plants suffer significant damage.

This has been the case in several fields in southwestern Kent County over the past couple of weeks. Of particular interest is a field shown in the photographs below. The field developed striping across it on 30-inch centers (Photos 1, 2, and 3). In some areas, plants between the “rows” died and disappeared (Photo 4) and in other areas plant growth was slower other than in the “rows”. As can be seen in the photos, the rows are very straight and on 30-inch centers. We think the pattern follows where starter fertilizer was applied next to the corn rows last year since the lines are very straight. Rather than residual nutrients, the effect is very likely due to the slight acidulation of the soil that surrounded the banded starter fertilizer. The slightly lower pH in these areas has increased Mn availability just enough so that the plants were healthy enough to survive until the field received foliar Mn about a week before the photographs below were taken. Between the ‘rows” where banded starter did not affect Mn availability, the plants were so stressed for Mn that the N application caused them to die.

This week we took additional soil samples to investigate whether we can detect the small pH differences expected and we will report on the results in a future issue of Weekly Crop Update.

A concern that the grower may have is whether the Mn deficiency will show up in double-cropped soybeans if they are planted after the barley. First, the foliar treatment on the barley will not have any effect on a future crop. Second, a soybean crop is subject to Mn deficiency but whether the soil Mn levels are low enough for symptoms to appear is still in question. Barley seems to be more sensitive than soybean so visual symptoms may not been seen in the soybean plants. However, there is a strong possibility that the soybean crop will suffer from what is often referred to as “hidden hunger’. This occurs when the soil Mn availability is not quite low enough to stimulate visual symptoms but is at the critical range where yield potential is lowered without visual symptoms appearing. Our recommendation is that either the grower should consider a broadcast application of Mn (usually for a broadcast application 30 lbs actual Mn is applied per acre) so that soil Mn levels are increased above the critical range or the grower should plan on a foliar Mn application around the fifth leaf stage (V-5) when enough leaf area is present to adsorb adequate Mn from a foliar application. One to two pounds of actual Mn is the suggested rate for a single application. This rate is suggested since application costs are more than the cost of the product and so a single application will be the preferred method.

Photo 1. Barley rows generated following renewed spring growth and nitrogen application showing effect of last year’s starter fertilizer.

Photo 2. Barley between corn rows was either severely Mn deficient or had died while barley on rows 30 inches apart grew vigorously.

Photo 3. Wide view of barley field with old corn rows showing vigorous barley growth.

Photo 4. Between the “rows” barley Mn deficiency symptoms following spring N application were severe.

Wheat Nutrition – Adding an Extra Touch

Wednesday, March 26th, 2008

Richard Taylor, Extension Agronomist;

With the current wheat price, many producers may be thinking of adding extra nitrogen (N) to push yield potential to the maximum. The high cost of N actually could limit any gain from this approach since we know that in most cases what limits yield are the environmental (water-primarily-and temperature) conditions during grain fill and not N availability. Wheat yield, like corn, responds to additional N in a way that for each additional pound of N applied the incremental increase in yield becomes smaller and smaller until the point of maximum economic yield (MEY). After the MEY point, although more N may increase yields slightly, the extra N actually reduces net profit per acre. (more…)

Nitrogen Applications to Wheat in a Cover Crop Program that Restricts Fertilization Until Mid-March 2008

Wednesday, March 26th, 2008

Richard Taylor, Extension Agronomist;

A number of fields were seeded this past fall to winter wheat after being enrolled in cover crop programs that excluded fall applied nitrogen (N). Some fields were seeded quite early in the fall and tillered profusely while other fields were seeded late enough or in dry soil so fall growth, and especially tiller production, was very limited. As late-planted or untillered fields begin to emerge from winter dormancy, N availability will be critical to encourage rapid growth and tiller development in the spring of 2008 for those fields that will be allowed to be harvested for grain. Virginia Tech’s publication entitled “Intensive Soft Red Winter Wheat Production” provides some valuable information to assess the N status of wheat fields in early spring. (more…)

Wheat Nutrition – Secondary Macronutrients and Micronutrients

Wednesday, March 12th, 2008

Richard Taylor, Extension Agronomist;

Sulfur (S)
In past years, quite a few small grain fields located on sandy soils in both Delaware and Maryland have shown large areas of yellowed, stunted plants for both wheat and barley. Usually symptoms are noticed or appear shortly after spring fertilization with nitrogen (N). In many cases, deficiency of either S or Mg has been confirmed with both tissue and soil samples. Examples of fields showing classic deficiency symptoms for S are shown in photos 1 to 4. The symptoms include stunting of plants, general yellowing or chlorosis especially of the new growth (remember that S is immobile in the plant causing symptoms first to occur on new growth but when deficiencies are severe symptoms can involve the whole plant), and poor root development. In the barley shown in Photos 1 through 4, the root systems of the affected plants were limited to the upper 2 to 4 inches and the soil type was loamy sand.