20 Jun 2014

Production Pointers - Dr. T. Scott Murrell

Starter Fertilizer FAQ

Starter fertilizer is a term used to describe nutrients that are placed in a concentrated band near the seed during planting. This series focuses on answering common questions about this management practice.

June 20, 2014 Question – Will starter fertilizers contribute to phosphorus problems in surface waters?
A: Losses of phosphorus can be controlled by implementing erosion control measures as well as using practices that reduce surface runoff. Because starter fertilizers are placed more than an inch below the surface, the phosphorus in them is not readily lost to other places in the environment.

June 10, 2014 Question – Do I still need to use starter fertilizers if my soil test levels are high?
A: Depending on environmental conditions and the crops grown, starter fertilizers can provide benefits even at high soil test levels. Young plant root systems explore only a small amount of the soil early in the season, so bands of nutrients near the seed are uniquely accessible. In addition, roots of some crops, like corn, take up nutrients very quickly early in the season, increasing the importance of concentrated supplies. Cool and wet conditions early in the season limit root growth and increase the chances that crops will respond to starter fertilizer, even at higher levels of soil test phosphorus.

June 1, 2014 Question – Are in-furrow applications as effective as other placement methods?
A: In-furrow applications may be best for some crops and not others. For instance, sugar beets respond well to low rates of phosphorus placed with the seed – as well as much higher rates broadcast; however, soybeans are generally too salt sensitive to respond well to in-furrow applications. Crops differ in their root architecture, how quickly roots take in nutrients at various growth stages, and salt sensitivity. Getting to know the characteristics of each crop is key.

May 20, 2014 Question – Can starter fertilizers become my complete fertilizer program?
A: In the first year, crops can recover a large amount of the fertilizer applied as starter. When this happens, larger returns to an initial investment in nutrients can be realized. However, the low rates used may limit overall yield and revenue if the overall fertility of the soil is low. Long-term sustainability of soil fertility can be compromised if starter fertilization is the only phosphorus and/or potassium nutrient management strategy.

May 10, 2014 Question – How do starter fertilizers work?
A: Starter fertilizers work by providing a small quantity of concentrated nutrients very close to a young, developing root system. Once roots explore the band of nutrients, they will proliferate there, as long as nitrogen and/or phosphorus are present. Because root contact with the fertilizer is important, nutrients must be placed where roots can access them. The best placement may be different for different crops.

May 1, 2014 Question – What are the benefits of starter fertilizer to crops?
A: The primary benefit of starter fertilizer is hastened maturity of crops. Earlier maturity can lead to increased yield and lower grain moisture at harvest, depending on growing conditions. The economic benefits are increased revenue and savings on drying costs. Cost savings for drying are greater when fuel prices are higher. Because so much of the response to starter fertilizer depends on unforeseeable seasonal conditions, farmers adopting this practice typically make it a regular part of their nutrient management strategies.

April 20, 2014 Question – When is starter fertilization a good practice?
A: Traditionally, starter fertilizers have been shown to be most beneficial when early season growing conditions are unfavorable. Cool and wet spring conditions are the most commonly used example. Wisconsin research, however, has shown that longer-season corn hybrids planted late, are also responsive.

April 10, 2014 Question – Does the early season increase in growth translate to yield increases?
A: Many comment that starter fertilizers provide increased early season growth. This is often observed when crops grown with and without starters are compared side-by-side in the field. The increased growth does not necessarily mean that the end of season yield will be higher. Later season growing conditions will dictate the extent, if any, of the yield increase.

April 1, 2014 Question – How much fertilizer can I apply as a starter?
A: Generally, rates must decrease as placement gets closer to the seed, as soils become drier, as texture becomes more coarse, as the salt index of the fertilizer increases, and as the salt sensitivity of a crop increases. In-furrow applications, where the fertilizer is in direct contact with the seed, are the most restrictive for rates. Specific guidance should be obtained from university extension publications. A calculator for estimating safe rates of various fertilizers is available at: http://www.sdstate.edu/ps/extension/soil-fert/index.cfm.


March 20, 2014 – What can I expect when skipping a P or K application?
The need for a future investment into the soil nutrient bank. Farmers who own ground often say that their fields are their 401K plans. A similar concept applies to nutrients. When prices are more favorable, soil nutrient supplies can be built up. That way, when markets become unfavorable, the less expensive soil nutrient reserve can be drawn down. But just like a bank account, withdrawals can be made for only so long. Once nutrients get below the “minimum balance,” the crop incurs a yield penalty. Managing the soil nutrient supply should be done with the same vigilance as managing a personal bank account. It’s okay to withdraw – just make sure your nutrient “check” doesn’t bounce.

March 10, 2014 – What can I expect when skipping a P or K application?
The need for a more complete starter fertilizer package: A lot of starter fertilizer formulations contain only nitrogen (N) and P. If one or more K applications have been skipped, consider adding K to the starter fertilizer mix. If K is added, pay attention to changes in the salt index of the fertilizer blend. It may be necessary to switch from placement in direct contact with the seed to a placement farther away, such as 2 in. to the side and 2 in. below the seed, to avoid seed injury.

March 1, 2014 – What can I expect when skipping a P or K application?
Greater importance of starter applications: Applying nutrients near the seed at planting provides a more concentrated band of nutrients that is in a good position for early season access by young, limited root systems. Applying starter fertilizer is a good approach to managing nutrient variability, particularly if it is suspected that a soil test may not be capturing all lower testing areas or if it has been awhile since a soil test has been taken.

February 20, 2014 – What can I expect when skipping a P or K application?
The need to be more watchful: Foregoing a management practice like a nutrient application requires frequent reevaluation. Keep an eye out for signs of crop stresses during the season, by using visual observations for nutrient deficiency symptoms as well as tissue testing. Ensure also that soil tests are up-to-date.

February 10, 2014 – What can I expect when skipping a P or K application?
Effects on crop response to nitrogen (N): Nutrients interact, meaning that their combined effects are greater than their individual ones. If either K, P, or both become insufficient, plant responsiveness to N gets compromised, resulting in reduced yield and/or quality. If only small quantities of P and/or K can be afforded, it is best to place them near the seed at planting, such as 2 in. to the side and 2 in. below the seed, as is often recommended for corn.

February 1, 2014 – What can I expect when skipping a P or K application?
Effects on plant health: Proper nutrition is tied to decreased severity or improved resistance to a number of crop diseases. A commonly observed problem when potash applications are inadequate is lodging of corn as harvest nears. It has also been shown that aphids are more attracted to soybeans that are K deficient. Like humans, plants have the greatest chance of being healthy when they are properly fed.

January 20, 2014 – What can I expect when skipping a P or K application?
Effects on soil tests: Over time, soil tests will decline to reflect the drawn down of soil reserves. Soil tests are generally more sensitive to such changes at higher levels. Year-to-year noise in soil tests is less for P than it is for K. The K soil test is more affected by temperature and moisture conditions than is the P soil test, so don’t be alarmed if a K test comes back with a result you didn’t expect. Keep testing as often as you can afford to. Over time, the trend will become more apparent.

January 10, 2014 – What can I expect when skipping a P or K application?
Effects on nutrient budgets: Crops remove nutrients with every harvest. Failing to replenish what crops remove erodes soil nutrient supplies. When native nutrient supplies are high or if soil fertility has been built up, relying on soil supplies is a good practice but can be done for only so long. Use soil tests to monitor how quickly reserves are being drawn down and keep track of nutrient removals.

January 1, 2014 – What can I expect when skipping a P or K application?
Effects on crop yields: Crop yields may or may not see a decline. If soil tests have been built up to levels that are considered non-limiting, then there is a very small probability that yields will suffer if P or K is omitted. If P or K has been omitted in previous seasons and it has been awhile since you’ve taken a soil test, it’s time to reevaluate the nutrient status of your soils. Fields or field areas with lower soil tests run a higher risk of yield loss if P or K is omitted.

December 20, 2013 – Long-Term Study Shows Potassium Fertilization Maintains Soil Mineralogy
The Morrow Plot Experiment in Illinois has been carried out since 1876. The study examines different crop rotations and fertilizer management practices. Changes in soil mineralogy were evaluated between 1913 and 1996, a period of 85 years. In a continuous corn treatment without fertilizer, the soil lost some illite and gained some smectite. In an accompanying continuous corn treatment that had received nitrogen, phosphorus, and potassium (K) fertilizers since 1955, the mineralogy was indistinguishable from that in 1913.

Illite is a mineral that contains potassium. It is hypothesized that repeated grain harvests without K fertilization resulted in the release of K from illite, transforming it to smectite. Where K had been applied, the original illite content was preserved.
    Source: Velde, B. and T. Peck. 2002. Clay mineral changes in the Morrow Experimental Plots, University of Illinois. Clays Clay Miner. 50:364-370.

December 10, 2013 – Banding Phosphorus Fertilizers Can Release Potassium from Soil Minerals
The chemistry in fertilizer bands is much different than in the bulk soil. Higher concentrations of fertilizer can produce some interesting reactions. Our understanding of these reactions is progressing through carefully controlled laboratory studies. One such investigation has revealed that high concentrations of monoammonium phosphate (MAP), diammonium phosphate (DAP), and monocalcium phosphate in bands can release potassium (K) from some clay minerals commonly found in soils. The minerals releasing K are mica, illite, and microcline (a feldspar). The reaction appears to be driven primarily by the interaction of acid ions and the phosphate molecule. The acid ions weaken the chemical bonds in the mineral. These weakened bonds make the minerals susceptible to reactions with phosphate that break the structural bonds. Since these minerals contain K, as the mineral structure is broken down, K is released. In the case of mica and illite, this K comes from the interlayers between molecular sheets. Microcline does not have this sheet structure. Instead, it is a feldspar that has a three-dimensional order and it appears only the surface bonds are affected.

In many past studies, bands of phosphate have resulted in greater agronomic efficiency. It may be that part of the benefits of banded P actually comes from greater availability of K. Future research will help shed light on these reactions and the many others that occur in fertilizer bands.
    Sources: Zhou, J.M. and P.M. Huang. 2007. Kinetics of potassium release from illite as influenced by different phosphates. Geoderma 138:221-228.
    Zhou, J.M. and P.M. Huang. 2006. Kinetics and mechanisms of monoammonium phosphate-induced potassium release from selected potassium-bearing minerals. Can. J. Soil Sci. 86:799-811.

December 1, 2013 – Laboratory Study Investigates Anhydrous Ammonia and Potassium Interaction
Nutrient interactions are often overlooked in research. Two older laboratory studies investigated how anhydrous ammonia (AA) and potassium (K) interacted when placed together in a band. It doesn’t appear that any field studies were conducted as a follow up, so whether or not these effects last long enough to make a difference in production settings has yet to be determined. While we don’t know of a commercial applicator engineered to perform this operation, it is a nice demonstration of some key reaction mechanisms in soils.

The study examined a solution of potassium chloride (KCl) banded either alone or with anhydrous ammonia. The rate of K was 103 lb K2O/A and that of AA was 200 lb N/A, based on a 30 in. knife spacing. The soil we highlight here contained 3.2% organic matter, and the following percentages of clay minerals: 15% smectite, more than 35% illite and mica, 10% vermiculite, and less than 5% kaolinite. Both ammonium and K can move into the layers between individual molecular sheets of both smectite and vermiculite. When K moves into the interlayers, it is not as rapidly available to plants as when it is in solution or bonded to the edges and outer surfaces of the clay minerals. So limiting the amount of K that goes into the interlayers increases its short-term availability.

What the researchers observed in these studies is that when AA was co-applied with KCl in a band, ammonium preferentially entered the interlayers of the clay minerals, limiting the amount of K that entered. This left more of the K in solution and on the edge and surface sites of the clay minerals, increasing its plant availability.

There was another factor at work. When AA reacts with water in soil to form ammonium, a basic solution, typically pH 8 to 9, is produced in the band because the reaction consumes acid cations. This shift in pH increases the negative charge of the organic matter. Potassium is positively charged, so it is attracted to it; however, the nature of the negative charge on the organic matter actually results in a preference for calcium (Ca), which is also positively charged. So if both K and Ca are near a negative charge on the organic matter, Ca, rather than K, will bond. This also contributes to more K ending up in solution and on the edges and surfaces of clay minerals. The band eventually becomes acid as ammonium is converted to nitrate, limiting the time for this mechanism to impact K availability.

The combined effects of both the ammonium entering the interlayers of clay minerals and the preference for Ca to be bound to organic matter under basic soil pH levels increase K availability. These effects lasted about four weeks in the experiment. Whether or not this effect is long enough and/or occurs at a sufficient magnitude to produce yield increases to K has yet to be proven.
    Sources: Stehouwer, R.C. and J.W. Johnson. 1991. Soil adsorption interactions of band-injected anhydrous ammonia and potassium chloride fertilizers. Soil Sci. Soc. Am. J. 55:1374-1381.
    Stehouwer, R.C., S.J. Traina, and J.W. Johnson. 1993. Potassium adsorption and exchange selectivity within an anhydrous ammonia fertilizer band. Soil Sci. Soc. Am. J. 57:346-450.

November 20, 2013 – Potassium Fertilization Can Modify Soil Minerals
We often think that the mineralogy of a soil is fairly static. We of course know that over hundreds and thousands of years, weathering will change the composition of soils, but are more short-term changes possible? It turns out the answer is yes.

A study was conducted in France that examined the effects of potassium (K) fertilization as well as K depletion on soil mineralogy. Within 7 days, K fertilization had changed some of the soil mineral smectite to illite.

Smectite is a mineral composed of an aluminum hydroxide sheet sandwiched between two silicon oxide sheets. In soils, these sandwiches stack on top of one another and are separated by molecular layers of water. A portion of this added K displaces the water, and the stacks of sandwiches bond to the K between them. This bonding decreases the distance between sandwiches, forming a new mineral illite. But there’s more.

The study also examined what would happen to the newly formed illite when plants were grown and took up K from the soil. Within 14 days, some of the illite had reverted back to smectite. So it seems that not only can fertilization change soil mineralogy but plant uptake can also. Instead of looking at soil minerals as relatively unchanging, a more accurate picture is that soil minerals are dynamic, responding to K fertilization as well as to removal of K by crop uptake.
    Source: Barré, P., B. Velde, N. Catel, and L. Abbadie. 2007. Soil-plant potassium transfer: impact of plant activity on clay minerals as seen from X-ray diffraction. Plant Soil 292:137-146.

November 10, 2013 – Why Do Changes in Soil Mineralogy Matter?
Research has shown that potassium (K) fertilization can transform smectite minerals into illite minerals. The reverse has also shown to be true: lack of fertilization can transform illite minerals to smectites. This at first may seem to be of only academic interest; however these changes have profound effects on K availability to plants with wetting and drying cycles in soils.

When soils are wetted, smectites fix K in their interlayers, making it temporarily unavailable for plant uptake. Illites behave oppositely, releasing K from their interlayers. When soils dry, smectites release K while illites fix it.

For any given soil, the net impact of these opposite reactions will vary and will depend on how much of each mineral is present. But it is important to recognize that K will not behave the same in every soil under wet and dry conditions, and that its behavior will also depend on past K management.

While science continues to unravel more about how wetting and drying cycles affect soil minerals differently, the effects above should be kept in mind as we manage soil fertility and evaluate it with soil testing.
    Source: Shen, S. and J.W. Stucki. 1994. Effect of iron oxidation state on the fate and behavior of potassium in soils. p. 173-185. In J.L. Havlin and J.S. Jacobsen (eds.) Soil testing: Prospects for improving nutrient recommendations. SSSA Spec. Publ. 40. SSSA, Madison, WI.

November 1, 2013 – Bands of Potassium Applied near a Corn Row May Not Last
We often think that a band of potassium (K) fertilizer will stay around for more than one cropping season. A recent study from Pennsylvania examined the residence time of a low rate of K applied as a starter fertilizer. Potassium was applied 2 in. to the side of the corn row and 4 in. below the soil surface during seeding. Annually applied rates ranged from 11 to 23 lb K2O/A. Potassium was co-applied with 11 to 22 lb nitrogen (N)/A and 23 to 33 lb P2O5/A. Applications were made repeatedly in 23 of the 25 cropping seasons. In the other two cropping seasons corn was not grown. Soil samples were taken in transects across crop rows at three depths in order to quantify the concentrations and spatial extents of fertilizer bands. The P bands were evident in the 0 to 2 in. soil sample depth in all three of the tillage systems studied: 1) no-till, 2) chisel-disk, and 3) moldboard plow/disk; however, K did not show an enriched area where it had been banded. Instead, the enriched area was in the actual corn row, and this phenomenon occurred in all three tillage systems. What happened?

First of all, K diffuses several times faster in soils than P, contributing to the disintegration of the band. But perhaps most importantly, the plant itself seems to have redistributed the K. Because the K had been co-applied with both N and P, it is likely that roots proliferated in the band, increasing the amount of fertilizer K that was taken up from it. After the corn crop reached maturity, K began to leach out of plant tissues with each precipitation event. This leached K seems to have been deposited primarily in the crop row. So the combination of 1) greater K movement in soil and 2) redistribution of K by plant uptake and subsequent leaching may explain the shift of the concentrated zone of K from the area where it was originally banded.
    Source: Duiker, S.W. and D.B. Beegle. 2006. Soil fertility distributions in long-term no-till, chisel/disk and moldboard plot/disk systems. Soil Tillage Res. 88:30-41.

October 20, 2013 – Crops Don’t Always Respond to Potassium Fertilizer on Sandy Soils
We often associate acid, sandy soils with low nutrient supplies. We generally consider the crops grown on them to have a high probability of yield response when fertilized. But there have been some cases where crops don’t respond at all on sandy soils with marginal soil potassium (K) test levels. One theory suggests that the feldspar minerals present in some sands may be supplying the needed K. The mechanisms aren’t well known, but some evidence suggests that under acid conditions, the acid cation (H3O+) may exchange with K in the feldspar structure, since it is about the same size and has the same charge. It appears also that the amount of K accessed from feldspars varies with the types of plants grown. Another source of K in some sands is the clay mineral illite, which contains K between individual crystalline layers. This K, although traditionally considered “fixed” is actually available under certain conditions. The message science provides so far is that just because a soil is sandy doesn’t necessarily guarantee that crops grown on it will respond to K fertilization. There are a lot of variables at play.
      Doremus, R.H. 1998. Comment on “stationary and mobile hydrogen defects in potassium feldspar” by A.K. Kronenberg, R.A. Yund, and G.R. Rossman. Geochim. Cosmochim. Acta 62:377-278.
      Lewis, C.C. and W.S. Eisenmenger. 1948. Relationship of plant development to the capacity to utilize potassium in orthoclase feldspar. Soil Sci. 65:495-500.
      Rasmussen, K. Potash in feldspars. p. 57-60. In. Potassium in soil: Proc. Colloq. Int. Potash Inst., 9th. Landshut, Germany. Available online at http://www.ipipotash.org/udocs/potassium_in_soil.pdf (verified 27 Sep. 2013).
      Rehm, G.W. and R.C. Sorensen. 1985. Effects of potassium and magnesium applied for corn grown on an irrigated sandy soil. Soil Sci. Soc. Am. J. 49:1446-1450.

October 10, 2013 – Are Annual Applications of Potassium More Efficient?
Agronomic efficiency is the increase in yield per unit of potassium (K) applied. Most assessments consider only the increase in yield for the one season in which K was applied. However, K can have positive effects on yield for many seasons beyond the season in which it was applied. Higher rates have longer-lasting effects. A study conducted in a corn/soybean cropping system in Iowa demonstrated that the residual effects of higher rates of K were essentially equal to annual applications of lower rates of K. While the original study did not conduct this evaluation, all information to do so was provided. Considering the yield increases of both the corn and soybean crops, residual effects of larger K applications had an agronomic efficiency of 0.17 bu/lb K2O, while the agronomic efficiency of annual applications of lower rates was 0.18 bu/lb K2O. This comparison was made over a 10-year period and the total amount of K2O applied during that period was the same for both rates.
      Source: Mallarino, A.P., J.R. Webb, and A.M. Blackmer. 1991. Soil test values and grain yields during 14 years of potassium fertilization of corn and soybean. J. Prod. Agric. 4:560-566.

October 1, 2013 – How Much of the Applied Potassium is Taken up by Corn?
Recovery efficiency is the percentage of the applied fertilizer that actually gets taken up by the crop. It is estimated by subtracting the total nutrient uptake of an unfertilized crop from that of a fertilized crop then dividing by the fertilizer rate. Calculated this way, it considers only one season and does not account for residual effects, which can be significant for potassium (K). Scientific reviews of K recovery efficiency are hard to find; however, a review published in the Netherlands found that the K recovery efficiency of corn averaged 34% ± 19%. Recovery efficiency is expected to change with K source, rate, application timing, and placement.
      Source: van Duivenbooden, N., C.T. de Wit, and H. van Keulen. 1996. Nitrogen, phosphorus and potassium relations in five major cereals reviewed in respect to fertilizer recommendations using simulation modeling. Fert. Res. 44:37-49.

September 20, 2013 –
Should I be taking more than one soil sample from a field? Yes. Researchers and crop advisers have found that even in relatively even looking fields, there is enough variability that more than one sample is needed. Historical manure applications, consolidation of smaller fields, and old building sites are examples of human influences on soil test variability. Topography, soil type, drainage patterns, and erosion are examples of natural sources of soil test variability. There are many approaches to taking more intensive sampling. You may decide to adopt one of the many existing strategies, such as grid or zone sampling, or you may decide just to take one or two more representative samples from the field. Whichever you choose, taking more samples from a field will help you begin to refine your P and K management to put nutrients where they are needed most.

September 10, 2013 –
What are the best placement options for P and K in no-till? In fields where no-till has been in place for several years, nutrient stratification can be significant, with very high concentrations near the surface decreasing to much lower concentrations just a few inches down. In irrigated or higher rainfall areas, root proliferation is nearer the surface, closer to larger nutrient supplies. In these instances, broadcast applications can be very effective. However, in non-irrigated and drier regions, roots proliferate deeper in the soil as the season progresses, farther away from higher nutrient concentrations. In these situations, deep banding (6-8 inches deep) P and K places nutrients nearer areas of active root uptake. To get an idea of the degree of stratification as well as P and K soil supplies present in a field, soil samples should be taken at various increments (such as 0-3, 3-6, 6-12, 12-24 inches) in a few locations. In soils with lower soil P and K supplies deeper in the profile, deep banding P and K is expected to be more effective.

September 1, 2013 –
What are the best placement options for P and K in ridge-till? Banding P and K from 4 to 6 inches deep in the center of the ridge is probably best. This puts P and K below the surface, where actively growing roots can quickly find needed supplies. Such subsurface applications also reduce risks of nutrient losses through runoff and/or erosion. Also, in ridge till systems, P and K nutrient supplies tend to be lowest in the ridge and highest between ridges. Therefore, applications in the ridge place nutrients where soil supplies are most limiting.

August 20, 2013 –
What are the primary benefits of testing soils for P and K? Soil tests provide two key pieces of information: 1) an index of P and K availability in the soil, and 2) a probability that crops will respond to P and K additions. Soil tests do not indicate how much P and K are actually in the soil, nor are they good for quantifying yield responses to nutrient additions in a particular year. Lower soil tests indicate soil P and K supplies are less available to plants and that there is a good chance crops will respond favorably to broadcast P and K additions. Without soil test information, P and K nutrient management becomes a guess.

August 10, 2013 –
If I’m growing soybeans next year, should I fertilize this fall? Many farmers let their soybeans “ride” on current soil P and K supplies and do not think about fertilizing for them specifically. Because of the nature of soybean root systems, broadcast applications of P and K are often superior to other placement methods, and in deficient soils, soybeans can be very responsive to fertilizer applications. Soybeans are an economically important crop and should receive as much attention to nutrient management as other crops in the rotation.

August 1, 2013 –
Should I apply P this fall? Fall is a good time to apply P. The drier soils typical of the fall reduce risks of soil compaction when application and tillage equipment cross the field. Phosphorus stimulates the proliferation of roots, so to get the most benefit from a P application, it’s important that root growth not be restricted by poor soil structure arising from compaction. Fall applications of P are appropriate for soils where runoff and erosion are not likely.

July 20, 2013 –
Should I apply K this fall? Fall is a good time to apply K. Soils are typically drier, facilitating fertilizer applications and tillage operations. Soils with a very low cation exchange capacity (CEC), such as sandy soils, as well as organic soils should not receive fall applications of K, since they can’t hold K very effectively over the winter. Fall applications of K are appropriate for most other mineral soils where runoff and erosion are not likely.

July 10, 2013 –
What risks are reduced with fall applications of P and K? Spring is often crammed full with fertilization, tillage, planting, and pest management. Fall extends the time to complete needed tasks for next year’s crops. Applying immobile nutrients like P and K in the fall to areas with low risks of nutrient losses is an agronomically sound practice that shifts some of the management load from the spring to the fall. This provides added flexibility in the spring when there are fewer days appropriate for field work. Drier conditions in the fall also reduce risks of soil compaction as equipment is run across the field.

July 1, 2013 –
Do I need to apply K and P after a poor crop? In drought affected areas, crop yields have been greatly reduced. This means that crop harvest may remove fewer nutrients than expected earlier in the year. When such unexpected events occur it is important to gather some information to re-assess the situation. Taking soil samples is a must. Remember that soil test levels reflect not only this year’s nutrient changes but also historical management practices. The P and K left over from last year’s application may pale in comparison to several years’ history of mining soils to reduce costs during low crop prices. Soil test results provide the information necessary to plan fertilization practices for the next season.

June 20, 2013 – The April through June series of Quick Tips for the North Central Region focuses on zinc nutrition.
When soybean is harvested, zinc (Zn) is removed from the field. The amounts of Zn removed by soybean under different harvest scenarios are estimated in the table below. Values in columns reflect the different Zn removal estimates by different state university Extension publications.

June 10, 2013 – The April through June series of Quick Tips for the North Central Region focuses on zinc nutrition.
When corn is harvested, zinc (Zn) is removed from the field. The amounts of Zn removed by corn under different harvest scenarios are estimated in the table below. Values in columns reflect the different Zn removal estimates by different state university Extension publications.

June 1, 2013 – The April through June series of Quick Tips for the North Central Region focuses on zinc nutrition.
For assessments of zinc (Zn) nutrition of soybean, samples of the uppermost trifoliate leaves at early bloom have traditionally been recommended. The sufficiency ranges for Zn concentrations in trifoliate leaves are given in the map below for several states with Extension publications providing guidance. All values are in parts per million (ppm).

May 20, 2013 – The April through June series of Quick Tips for the North Central Region focuses on zinc nutrition.
For late-season assessments of zinc (Zn) nutrition of corn, ear leaf samples have traditionally been recommended at silking. The sufficiency ranges for Zn concentrations in ear leaves are given in the map below for several states with Extension publications providing guidance. All values are in parts per million (ppm).

May, 10, 2013 – The April through June series of Quick Tips for the North Central Region focuses on zinc nutrition.
Zinc (Zn) is a micronutrient. Plants take up much less of it than they do macronutrients like N, P, and K. Average quantities of Zn taken up by corn, soybean, wheat, and alfalfa are shown below. Values in columns reflect the different Zn uptake estimates by different state university Extension publications.

May 1, 2013 - The April through June series of Quick Tips for the North Central Region focuses on zinc nutrition.
Soil applications of zinc (Zn) can be broadcast or banded. Maximum recommended rates of banded Zn are provided in the map below. Rates are calibrated for annual applications of zinc sulfate. Values include those for calcareous soils, P levels below 150 ppm, and soil pH levels less than or equal to 7.5.

April 20, 2013 – The April through June series of Quick Tips for the North Central Region focuses on zinc nutrition.
Soil applications of zinc (Zn) can be broadcast or banded. Maximum recommended rates of broadcast Zn are provided in the map below. Rates are calibrated for zinc sulfate. The recommended frequency of Zn applications ranges from every three to five years across states. Values include those for calcareous soils, P levels below 150 ppm, and soil pH levels less than or equal to 7.5. The lower value for Virginia is for Coastal Plain soils and the higher value is for Piedmont or Appalachian Region soils.

April 10, 2013 – The April through June series of Quick Tips for the North Central Region focuses on zinc nutrition.
Soil testing is the tool most commonly used to evaluate zinc (Zn) soil fertility. Critical levels are the levels below which soil is considered deficient. Deficient soils require Zn additions. The map below shows the critical levels for soil tests in various states. All levels are in parts per million (ppm). The different colors denote university Extension interpretations for different chemical extractants used in soil testing. Illinois has interpretations for two extractants. Values include those for calcareous soils, P levels below 150 ppm, and soil pH levels less than or equal to 7.5.

April 1, 2013 – The April through June series of Quick Tips for the North Central Region focuses on zinc nutrition.
Zinc (Zn) moves to plant roots primarily by diffusion. Diffusion is movement from a zone of higher concentration to one of lower concentration. The majority of Zn taken up by plant roots moves by this pathway. Lower temperatures slow diffusion rates, so under cooler conditions, such as early spring, Zn applied near the seed at planting can be an advantageous placement.

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