Archive for the 'George Rehm' Category



Looking ahead to the 2015 growing season, there has not been a dramatic improvement in commodity prices.  And, at this time, I’m hearing grain market analysts that offer any hope of major improvement.  Likewise, the three major expenses in crop production (fertilizer, seed, land rent) have not changed much when compared to the last two or three years.  Crop producers are concerned and are asking if they can reduce rates of broadcast applications of phosphate and potash without having a negative effect on soil test values for phosphorus (P).  There has been some research conducted at the regional Experiment Stations that help in addressing this concern.  These data become more meaningful because the studies were conducted over a period of years starting in 1986 and terminating in 1993.

For this study, phosphate fertilizer, supplied as 0-46-0, was applied annually in a corn – soybean rotation at the Southern Research and Outreach Center (Waseca) as well as the West – Central Research and Outreach Center (Morris).  The 0-46-0 was to supply 50 and 100 lb. phosphate per acre.  There was also a control where phosphate was no applied.  Other nutrients were applied as needed to provide for optimum crop production.  Corn and soybean yields were measured and annual soil samples ( 0 to 6 inches) were analyzed for P.

This blog is written to describe changes in soil test P each year when phosphate application was terminated after the 1985 growing season.  Crop yield, of course, varied with location and weather during the growing season.  At the  Waseca location, corn yields were usually in the range of 180 bu./acre while soybean yield was in the range of 50 to 55 bu./acre.  At the Morris location, corn yield was about 160 bu./acre and soybean yield was about 50 bu./acre.

Soil test values for the Waseca and Morris locations are shown in Figures 1 and 2 respectively.  Some interpretation of the results is probably appropriate.  At Waseca, the soil test value for P (Bray test) was initially about 7 ppm.  With no phosphate applied, this value decreased by about 0.6 ppm per year.  This decline was about 2.25 ppm per year when the annual broadcast was 50 lb./acre prior to 1986.  When the phosphate rate at this site was increased to 100 lb./acre, the decline was 3.1 ppm per year.  These declines are shown in Figure 1.




Soil properties were at the Morris location.  There  was a higher  soil pH with elevated levels of calcium carbonate.   With no phosphate applied, the rate of decline in soil test P was .26 ppm per year.  Annual application of 50 lb./acre prior to 1986 had increased the soil test P value to 17 ppm.  Without additional phosphate, the decline was 1.5 ppm P per year.  Over the years, soil test P (Bray test) the use of 100 lb. phosphate annually had increased to 36 ppm.  The decline from this value was 2.7 ppm P per year when the phosphate application ceased.

Results from these two locations illustrate several points.  First and most importantly, if no phosphate fertilizer is applied, there is no steep drop-off in soil test P.  Decline is gradual and can be corrected with added phosphate when profit return to crop production.  If phosphate rates are reduced instead of eliminated, the reduction  in soil test values for P will be more gradual.  For those growers who have high or very high soil test values for P, the decline in soil test values will not be noticed in measured yields.  It is also doubtful if small declines in soil test P will affect yields unless soil test values are in the very low range.

Phosphate rates applied in the study are identified by the symbols on the respective lines.  For both locations, the solid diamonds are associated with the control treatment ( no phosphate applied ).  The white triangles ( both sites ) represent the treatment of 100 lb. phosphate applied per acre from 1974 through 1985.  The dark  squares represent the annual application of 50 lb. phosphate per acre during the same time period.

Again, the declines in soil test P shown in Figures 1 and 2 show what might be anticipated if application of phosphate fertilizer was stopped completely.  Dramatic declines in soil test P would not be a consequence of reduced rates.  A reduction in rate of phosphate would be a good practice in a plan to get profit from crop production in 2015.  A switch  to a banded application of phosphate is another management practice that is encouraged.  When switching to a band,   instead of a broadcast application, the phosphate rate can be cut in half without reducing yield.




Various products and/or concepts that pertain to crop production seem to cycle with time.  I’m never surprised.  There are foo-foo juice products that have disappeared only to appear sometime later under a different name.  Likewise, there are concepts that have been proven by research to be bogus.  Yet, they don’t die.  There appear again.  It seems that there are always some who attempt to make money from Minnesota farmers by selling revived foo-foo juice products or bogus concepts.  To paraphrase a line from a once-popular song: “everything old is new again”.

Recently, there has been a revived promotion of CATION EXCHANGE CAPACITY (CEC) and CATION RATIOS.  The CATION RATIO concept has sometimes been referred to as “BALANCED SOIL FERTILITY”.  So, some review of what we know about CEC and balanced cations is probably appropriate at this time.

The concept of CEC and it’s relationship to crop production was first researched in New Jersey in the mid-1940′s.  At that time, researchers measured the CEC of soils as well as the exchangeable cations (Ca++, Mg++, K+).    The CEC is a nearly constant property of soils that is directly related to soil texture.  Sandy soils have relatively low CEC values.  BY contrast, fine textured soils have high CEC values.  The exchangeable cation values (Ca++, Mg++, K+) vary with other soil properties — mainly soil pH.

In the New Jersey soils, the researchers measured the exchangeable cations in a “productive soil” and a “non-productive” soil.  They calculated the ratios of one cation to another.  For example, the ratio of Ca++ to Mg++ was 6.5 to 1.  Alfalfa was the test crop.  So, it was thought that a “productive” soil should have a Ca to Mg ratio of this value.  These researchers neglected one important piece of information.  This was that lime had been used on the “productive” soil but not on the “non-productive” soil and the sandy soil had an acid pH.  The lime supplied Ca++.  Do you suspect that productivity of the alfalfa crop was a consequence of the use of lime rather the magic ratios?  In the years that followed, numerous research projects were conducted through the Midwest for the purpose of investigating the effect of cation ratios on crop production.

There were the comparisons of fertilizer recommendations provided by various Soil Testing Laboratories.  Some followed the cation ratio concept.  Others Used the sufficiency approach based on the response of crops to measured levels of available nutrients by standardized, routine analytical procedures.  Although costs of fertilizer recommended by these approaches varied considerably each year for extended periods of time (14 years in Nebraska), crop yield was not affected.  Fertilizer recommendations based on the cation ratio concept were much higher than those that were based on the sufficiency approach.

The results of the Midwest research led to the conclusion that the ratio of one cation to another in soils had no effect on crop production.  Crop response to fertilizer was the result of the nutrient supply in the soil — not ratios.  Nutrient supply is measured by the standard analytical procedures.  The crop has no interest in ratios.  Given the uniformity of the conclusions of these research projects, it appeared that the “ideal ratio” or “balanced nutrient” concept was dead and had disappeared from our knowledge base that pertained to soil fertility and fertilizer use.

Land Grant universities in the northern and western Corn Belt have published reports that document the bogus nature of the ideal cation ratio concept.  Staff at Agvise Laboratories have worked hard and listed the links to these reports on the Laboratory web site.  The web address is: if anyone is interested in the detailed reports.

The concept of IDEAL CATION RATIOS has been thoroughly research for several crops.  There is consistency in the results of this research.  This concept is not in any way related to effective and economical fertilizer recommendations.  In fact, use of this concept has a high probability of producing less than optimum recommendations for use of potash fertilizers on sandy soils.

The concept of IDEAL CATION RATIOS as a basis for fertilizer recommendations is truly bogus and has no place in Minnesota agriculture.  Please use this ratio concept if you want to waste money on fertilizer purchases in 2015.  Those who advocate the use of this concept are not up to date in their understanding of modern principles of soil fertility.  They’re still working in the 1940′s.  It was WRONG THEN and it’s WRONG NOW.



In Minnesota, soil water has a major impact on crop production.  We affect soil water by irrigating the sandy soils and using tile drainage to eliminate excess water for situations where internal drainage is poor to very poor.  Soil water is also linked to concerns with environmental quality.  In fact, there are some misguided individuals who believe that tile drainage is the cause of all sediment reaching Lake Pepin.  So, it’s appropriate to take a detailed look at soil water and the relationship to crop production in this state.

We begin by recognizing that there is a  substantial amount of pore space in any volume of soil that is occupied by both air and water.  In general, any volume of soil is about 50% mineral and organic matter and 50% pore space.  After a heavy  rain, most of the pore space is filled with water  At this point, soils are pictured as being SATURATED.  At this point, soil pores are filled with water.  Depending on soil texture, some of the water drains through the soil profile.  This water is defined as GRAVITATIONAL water.  This is the water removed via tile lines when soil drainage is such that tile lines are needed for optimum crop production.  When all gravitational water is removed, the soil is defined as being at FIELD CAPACITY.

At field capacity, plants continue to use soil water.  Without added rainfall or irrigation, water use by plants continues and plants begin to wilt when the water supply in the soil cannot keep up with evapotranspiration.  There is a soil moisture content at which plant begin to wilt.  There is also a soil moisture content where wilted plants do not recover when water is added.  This moisture content is defined as the PERMANENT WILTING POINT (PWP).  Soil moisture percentage is not zero at PWP.  A film of water attached to soil particles is not available to plants and is not used by plants. Even in the driest conditions, there is still a small amount of water in the soil.  The moisture between field capacity and PWP is known as AVAILABLE WATER reported as inches per foot of soil.  Amounts of available water are affected by soil texture and are listed in the following table.  This table also lists the water present at PWP for the various soil textures.  Note that the silt loam texture — not the clay texture — holds the highest amount of available water.

Soil Texture and Soil Water

Nearly everyone recognizes that tile drainage removes excess soil water thereby stimulating the movement of oxygen (air) into the soil pores.  When water flow through tile lines stops, the “available water” remains.  This water, of course, is used by crops until the permanent wilting point is reached.  TILE DRAINAGE DOES NOT REMOVE  AVAILABLE WATER.   If we understand this fact, we cannot accept the nonsense argument that tile drainage causes excess removal of “available water”.  Therefore, tile drainage cannot be blamed for accelerated erosion of the banks of the tributaries that reach the Minnesota River, and, then, into Lake Pepin.

As plants grow, water is absorbed through the root hairs.  Oxygen is required for this absorption process.  With saturated soils, oxygen is either present in small amounts or not present.  Although there is plenty of water in these situations, it’s not easily used by plants.

If plants use more water than amounts supplied by  rainfall and/ or irrigation , roots must explore larger volumes of soil.  When the entire rooting zone contains moisture, the majority of the water used comes from the soil close to the soil surface.  If this is not adequate, roots grow deeper and absorb water from lower depths.

This pattern of water use has a relationship to tile drainage.  If tile drainage stimulates early root growth, early plant growth is enhanced with subsequent increases  in the use of soil water.  If more soil water is used by crops, less is available for loss through tile lines.  Thus, more water is used across the landscape and does not move into rivers and streams.



In October, I received a request from the Land Stewardship Project soliciting contributions.  Normally, I don’t pay much attention to letters of that nature.  However, there were some words and/or phrases that caught my eye.

To begin the letter writer stated: “I am writing  to you about the nearly silent, devastating destruction of our land that is happening every day.”  Sounds ominous doesn’t it?  The world as we know it may come to an end very soon.   The writer continues by describing “ bare, black fields  shedding huge amounts of life-sustaining topsoil to wind and rain” on a drive to western Minnesota.  “Huge amounts”—really?  Of course, the writer blames all of this degradation and destruction on the widespread use of modern practices.

These statements are obviously based on perception and emotion.  So, what are the facts?  To get some real world edge-of-field data , we turn to information gathered in the Discovery Farms-Minnesota initiative.  In this effort, fields of 11 cooperating farmers from across the state are being monitored.  The farms are representative of farm enterprises throughout Minnesota.  In this blog, I will discuss soil loss information collected from three of these farms.  Loss of nitrogen and phosphorus will be discussed in future blogs.

A farm in the rolling hills of southwestern Minnesota is the most recent Discovery Farm.  A flume was built at the edge of the field having about 25 acres.  Water flowing the flume was sampled and sediment concentration was measured.  From flow and concentration information it is possible to calculate soil loss in terms of pounds per acre.  In 2014, that loss was 73 lb./acre.  Of this total, approximately one-third was in the snow melt.  The remainder was measured in runoff following heavy rains falling between June, 14 and June 16 (about 8 inches).  This low amount of sediment soil loss is attributed to residue remaining on the soil surface as a consequence of the use of a no-till planting system.  Even though the silt loam texture in the field crusts easily and the crust reduces rain infiltration, the surface residue was effective was reducing soil lost due to erosion.  This can hardly be described as “devastating destruction”.

Now, let’s move from the rolling hills to the nearly level prairie of Blue Earth County.  There are 26 acres in this monitored field having a slope of 1.9%.  To date, information has been collected for three years.  This field is representative of many, many acres in southern Minnesota.  Sediment loss was 74 lb./acre, 76 lb./acre and 480 lb./acre for 2012, 2013, and 2014 respectively.  A substantial amount of this sediment loss was in the snow melt (40%) in 2014.  This cooperating farmer finishes hogs in confinement and all manure is injected followed by a chisel plow tillage operation.

In Goodhue County, we monitor a field from a livestock enterprise.  The soil has a silt loam texture and the field has a slope of 6.7%.  Hog manure is injected in an alfalfa/corn rotation.  The manure is used to supply nutrients needed for corn harvested for silage.  When in corn, the field is seeded to winter rye to minimize soil loss.  Sediment loss was 47 lb./acre, 21 lb./acre, 205 lb./acre and 307 lb./acre in 2011, 2012, 2013, and 2014 respectively.  The field was planted to corn in 2013 and 2014 .  This explains the jump in sediment loss for 2013 and 2014.  This loss was measured even though the field was planted to winter rye.  Again, a substantial amount of soil lost was measured in soil melt.

The Discovery Farm-Minnesota project measuring soil loss at the edge of the field has not found that bare fields are shedding huge amounts of life-sustaining topsoil.  On the contrary, the information collected has shown is minimal across this state.  This provides evidence that crop producers today, are using excellent management practices that keep soil on the landscape.

The information collected in the Discovery Farm-Minnesota initiative is real.  There is no perception and emotion to distort what is measured.



From time to time, critics of modern agriculture argue that modern production agriculture have severely reduced or destroyed soil organic matter thereby causing harm that cannot be repaired.  This important component of soils has been measured in numerous studies and observations.  The conclusions do not support this argument.  But, before changes in soil organic matter can be discussed, it would be good to go back and look at some of the basics.

Most of the organic matter in soils (on average, about 5% by weight)  exists as humus.  This is the dark material formed when microbes decompose plant residues added to the soil.  This material becomes attached to the mineral particles of the soil and, therefore, decays slowly over time.  In our soils derived from prairie vegetation, there was a fairly rapid decline when these soils were first put into production.  This decline , however, has slowed dramatically and, in many production systems, there has been a slow and gradual increase in the organic matter content of soils.

The benefits of soil organic matter (SOM) have been recognized for many years and can be briefly listed as:

1. SOM is a slow release form of nitrogen, phosphorus, and sulfur for both plant nutrition and microbial growth.

2. SOM increases the capacity of soil to hold water

3. SOM is a buffer against rapid changes in soil pH.

4. SOM acts as a cement holding silt and clay sized particles together thereby contributing to the granular structure of soils.  The granular structure increases pore space thereby increasing resistance to erosion, especially erosion by wind.

5.  SOM plays a major role in the soil’s ability to tie up or absorb potential pollutants.  It provides a safe storage place where microorganisms can degrade often toxic materials over time.

Usually, there are not too many opportunities to measure soil organic matter content in situations where data are collected over time.  We have that opportunity in the Discovery Farms-Minnesota project.  In the fields of cooperating farmers, soil samples are collected annually to determine if there are any changes in soil properties as affected by the crop management practices used by the cooperating farmers.

A Discovery Farm was started in Goodhue County in the fall of 2010 and, except for 2012, soil samples from a depth of 0 to 6 inches have been collected each year.  The crop rotation was alfalfa in 2010,2011 and 2012 with corn harvested for silage in 2013 and 2014.  Injected hog manure is used as the source of nutrients.  The organic matter was 3.1% in the spring of 2010.  This percentage was 3.9%, 2.9%, and 3.4% in 2011, 2013 and 2014 respectively.  This amount of variability  is frequently observed when soil properties are measured over time.  There was, however, no substantial drop in organic matter content over time.  This certainly does not match with the argument of some who believe that modern farming practices are destroying the organic matter content of our soils.

In fact, the amount of organic matter contained in the residue of today’s high yielding crops is largely returned to the soil with a potential to increase the soil organic matter content.  This is another plus for modern agriculture.






In Minnesota, manure has proven to be a valuable source of nutrients for crop production.  As commodity prices fall, efficient and economical application of nutrients becomes more and more important.  We don’t want to reduce nutrient applications to the point of having a negative effect on yield.  At the same time, there is no logical reason for applying more than is needed.  A renewed emphasis on manure use is one tool that can be used to provide for the most efficient use of nutrients.  Since manure will be applied to a considerable number of acres this fall, it seems appropriate to review some of the fundamental principles of manure use.

Any plan to apply manure should begin with a laboratory analysis of the material.  It’s easy to get in a hurry and skip this step.  However, the nutrient concentration in manures does change with animal species and diet.  An analysis of manure is not expensive; but, the information obtained can have a substantial impact on the rates applied.  There are several laboratories that will provide a rapid analysis of manures.  A representative sample is all that is needed.

“Book values” for nutrients in manure can be used as a substitute for actual analysis.  However, these values are averages of the analysis of many samples and accuracy is sacrificed if these values are used.

Method of application is a serious consideration in manure use.  The application method used has a substantial impact on nitrogen loss.  The amount of nitrogen lost is affected by depth of application , soil temperature, soil moisture and animal species.  This loss has been the focus of many research projects and loss percentages have varied with the research project.  A summary of some measured losses is provided in the tables that follow.  I’ve used various methods of handling poultry and swine manure to illustrate the effect of management.  Others may have different percentages.  The percentages listed, however, provide a good indication of how management affects nitrogen loss.  It should be pointed out that these losses are for nitrogen only.

Nitrogen from poultry manure

Nitrogen from poultry manure


For turkey manure, the amount of time between application and incorporation in the year of application has a substantial effect on nitrogen availability (see Table 1).   If there is no incorporation, only about 30% of the total amount of nitrogen is available to the crop following application.  The remainder is lost.  The availability increases to about 75% of the total N if the manure is incorporated within 4 hours after application.  This time interval between application and incorporation is not important in  the second and third years after application.  The residual effects of manure in these years can be detected with a soil test.   It’s obvious that poultry manure should be incorporated as soon as possible after application.  There is no logical reason to leave this manure on the soil surface.  This practice simply reduces the effectiveness of the manure while increasing the risk of having a negative impact on environmental quality.

Nitrogen from swine manure

Nitrogen from swine manure


With swine manure, nitrogen loss as affected by time between broadcast application and incorporation is similar.  Nitrogen availability is more than doubled if the manure is incorporated within 12 hours of application (see Table 2).

The injection of liquid hog manure is a popular practice and various equipment is available that will allow for some type of injection.  It’s interesting to note that nitrogen availability is higher if sweep rather than knife injection is used.  This might be a consequence of a higher concentration of manure in a band when the knife injection is used.

The results summarized in Tables 1 and 2 show the impact  of rapid incorporation.  While the impact of rapid incorporation is important, a speedy incorporation does not substitute for the importance of waiting until soil temperature drops below 50 degrees before any manure is applied.  The nitrate-nitrogen in manures cannot be forced to convert to ammonium-nitrogen regardless of soil temperature.  If soil temperatures are above 50 degrees, ammonium-nitrogen and urea-nitrogen can convert to nitrate-nitrogen thereby increasing the probability of increasing nitrogen loss and reduced efficiency.

In mid-September, while driving through west-central Minnesota, I watched as poultry manure was being applied to several fields.  The soil temperature was certainly higher than 50 degrees.  There was going to be conversion from ammonium-nitrogen to nitrate-nitrogen.  It was also obvious that the manure would be incorporated.  The fields had been planted to sweet corn in 2014.  This kind of manure management will, in my opinion, stimulate the onset of strict regulations.  None of us want that.  The best management practices that are appropriate for the application of fertilizer nitrogen are also appropriate for the application of manure.



With current and projected commodity prices, many crop producers are exploring ways to cut fertilizer costs for the 2015 crop year and beyond.  In the previous blog, I briefly discussed some of the fertilizer management practices that could be used to keep fertilizer costs at a minimum.  This blog will focus on phosphate fertilizer management and the impact of the intended crop on phosphate fertilizer recommendations.

The table that follows lists phosphate fertilizer suggestion for three crops in Minnesota.  They are different.  Two soil test categories ( low, medium ) are used to illustrate these differences.  For each crop, two expected yields ( yield goals ) are used.  There are other soil test categories for phosphorus.  I’m assuming that there are very few fields where soil test values for phosphorus fall into the very low category.  Then, as soil test values move into the high and very high categories, relatively low rates of phosphate fertilizer are suggested.  Both Bray (B) and Olsen (O) soil test values for phosphorus are listed.

Selected phosphate fertilizer suggestions for three agronomic crops

Selected phosphate fertilizer suggestions for three agronomic crops










For  expected alfalfa yields of 6 or 7 ton per acre, there is a relatively small difference in the rate of phosphate fertilizer suggested.  This is true for both the low and medium soil test values for phosphorus.  Placement, of course, is not a consideration with the alfalfa crop.  A broadcast application combined with incorporation before seeding or a broadcast application to an existing stand is the only choice for placement.

The approach to phosphate application to corn is not the same as the approach used for alfalfa.  Placement has a substantial impact on the rate of phosphate suggested.  This is the case for both soil test categories for phosphorus that are shown.  The banded (starter) placement becomes more efficient as the soil test for phosphorus decreases.  For those few fields where the soil test for phosphorus is very low, a combination of broadcast and banded application is suggested.  These soils usually have a very high soil pH combined with a low organic matter content as well as other soil properties that restrict yield.  Thus, yield potential of these soils is limited.

The management practice of using a banded application as a substitute for a broadcast application can produce a considerable reduction in the money spent for fertilizer without a reduction in yield.  Therefore, a placement of phosphate in a band should be a serious consideration for 2015 as well as the near future.

There is no ideal location for the band It is not necessary to place it 2 inches to the side of and 2 inches below the seed.  Phosphorus is not mobile in soils.  So, placement on the soil surface above the seed after planting is not a good idea.  Placement of the band at seed level or below the seed is preferred.

Rates suggested for banded application will maintain, but not increase, soil test values for phosphorus.  But, that’s not a problem.  When fertilizer prices are high and commodity prices are low, it’s neither logical nor economical to apply phosphate fertilizer for the purpose of increasing or building soil test levels.

When considering the soybean crop, there are two points to consider.  First, there are no suggestions for a banded application of phosphate.  Substantial research conducted at the University of Minnesota has shown that for any given rate of phosphate, slightly higher yields will be achieved if a broadcast application is used.  This yield difference is usually in the range of 1 to 3 bushels per acre.  Secondly, there are no suggestions for phosphate use when the soil test phosphorus is in the medium range or higher.  With soil test values in these ranges, there has been no increase in yield when phosphate fertilizer is applied.  So, if soil test values for phosphorus are in the medium range, phosphate fertilizer is appropriate for corn–not soybean production.  From another viewpoint, if there is a good phosphate management program for corn, soil test values for phosphorus should be in the medium and range and there will be no need to apply phosphate for the soybean crop.

So, in looking ahead to 2015 and the near future, it’s important to consider the intended crop.  This could increase fertilizer use efficiency and save dollars.  All crops do not have the same phosphate requirements.  But, all planning for fertilizer management begins with a soil test.



The sharp drop in commodity prices has certainly been a major topic of conversation throughout farm country during this past summer.  The unanswered question is: ” How long will these extremely low prices last?”  Of course, I doubt if anyone knows the exact answer to this question.  However, there are some who predict that the low prices will persist for some time.  I certainly hope not.

Nevertheless, some forward planning is necessary if there is any anticipation of a profit for the years ahead.  I’ve asked several who are knowledgeable about input costs for projections as to what will change in the near future.  Most agree that there will have to be reductions in money spent for cash rent, seed, and fertilizer.  I readily admit that I’m no expert in cash rent and seed.  so, I’ll not comment on these two inputs.  But, I can provide some ideas for controlling and possibly reducing fertilizer costs.  These thoughts follow.

Any efficient and cost conscious fertilizer program, of course, begins with an accurate and comprehensive SOIL TESTING program.  This time tested management practice has been used before when times were tough.  There is no other logical way to get an inventory of the status of essential nutrients in soils.  There are several soil testing laboratories in the region that are in business for the purpose of providing an accurate analysis of soil samples.  It’s understood that there’s no universal agreement about the amount of fertilizer that should be applied when various ag-professionals interpret the results of analyses of soil samples.  Therefore, a SECOND OPINION is a good idea before any fertilizer is purchased this coming year and years in the near future.

Rain fall patterns during the 2014 growing season produced a loss of some of the applied nitrogen.  Exact amounts are impossible to predict.  This unknown places the emphasis on the SOIL NITRATE TEST.  This test is designed for an intended crop of corn follows any crop ( even fallow) that is not a legume.  This measure of carryover is very important.  An adjustment of rates of fertilizer N for the amounts of carryover nitrate-nitrogen in soils improves the efficiency of use of N fertilizer for corn.   Several factors affect carryover of nitrate-nitrogen.  Rather than speculate, have the necessary samples collected and analyzed.  The information gained could have a substantial effect on the bottom line.

We’ve known for many years that we should take NUTRIENT CREDITS when grain crops follow legumes and when MANURE is used in various cropping systems.  Nitrogen supplied by a previous legume crop can be substantial.  These credits are fairly consistent across the region.  They should not be ignored.

The quantity of nutrients supplied by manure is affected by several factors — most importantly the manure itself.  So, analysis of any manure used in cropping systems is a tool that can be used in developing cost-effective fertilizer programs.  Seek professional assisting in interpreting the results of manure analysis.

Take a close look at PLACEMENT of phosphate and potash fertilizers.  A substantial amount of field research conducted with Minnesota soils shows that banded application of P and/or K can produce substantial savings in fertilizer costs without reducing corn yields.  When soil test levels for P and/or K are in the LOW range the suggested broadcast rate can be cut in half if phosphate and/or potash fertilizers are applied in a band at planting instead of broadcast and incorporated before planting.  However, if soil test levels are VERY LOW, a combination of banded and broadcast applications may be needed.  Fortunately, there are few fields where soil test levels for these nutrients fall into the very low category.  For potassium, this is less than 40 ppm.  For phosphorus this is less than 3 ppm if the Olsen analytical procedure is used and less that 5 ppm if the Bray procedure is used.

A broadcast application of phosphate and potash will not be needed if soil test are in the MEDIUM,  HIGH, or VERY HIGH categories.  Banded applications will be adequate for these soils.

The previous statements apply when conventional tillage systems are used.  More emphasis is placed on banding when no-till, strip-till, and ridge-till planting systems are used.  These statements also apply to soil test categories defined by University of Minnesota standards.  Various private soil testing laboratories may use other standards.  There can be a substantial savings in money spent for fertilizer by using UNIVERSITY OF MINNESOTA standards which are based on considerable field research.  Others do not have this research base.

Don’t base fertilizer application rates on CROP REMOVAL.  Following the crop removal concept will produce the most expensive fertilizer recommendations.  The use of the crop removal concept ignores the importance of soil testing as a management tool and that’s just plain wrong.  Let’s give the soil itself some credit for supplying some of the total amount of a given nutrient needed for crop production.

In recent years, there seems to have been a major marketing effort for sale of MICRONUTRIENTS.  Of all the essential micronutrients,  there has been only one  which has been proven to be necessary for corn production.  Use of zinc in a band has increased yields on some, but not all, soils.  There has been no documented response to any of the other essential micronutrients.  Some marketing programs would like us to believe that the application of micronutrients can be beneficial if a foliar application is used.  Research in Minnesota  has not supported any beneficial effect from a foliar application of micronutrients.  Absorption of micronutrients through leaf tissue is very minimal.  The application of zinc, for example, has proven to be most effective if applied in a band at planting.

We’ve had to give close attention to fertilizer costs in years in the past.  In these years, the number of FOO-FOO JUICE products that were marketed increased dramatically.  Most have either changed their name or disappeared from the crop production scene.  Yet, some remain supported by testimonials without data and slick advertising.  Slick advertising does not equate to an effective product that will improve crop yields or increase efficiency of nutrient use.  Evaluation of any product in a well designed research program will document the benefits or lack of benefits.

Yes, it’s time to take a closer look at fertilizer costs in the near future.  It’s a near certainty that there will be attempts to convince us to spend money on fertilizer or fertilizer products that are not needed.  Don’t be confused.  If you’re not sure about something, don’t be afraid to ask questions.  Get a second opinion from another trusted ag-professional.  The savings in money spent could be substantial in 2015 as well as in the immediate future.




For the past few years, some have suggested that the use of glyphosate was harmful for crop production.  There were even suggestions that continued use of this beneficial herbicide would seriously impact our food production in the United States.  Sounds serious doesn’t it?  These statements were probably intended to grab headlines.  There were claims that this herbicide will interfere with nutrient uptake and increase diseases in the corn and soybean crops.  These claims seemed to  be backed by what might be considered to be a very weak research base.

Based on what is known about the mode of action of glyphosate, many scientists were skeptical about the negative claims.  To follow up, several studies were initiated by physiologists and chemists to document the impact of glyphosate use on nutrient uptake by the corn and soybean crops as well as the susceptibility of these crops to diseases.  The results of these scientific studies were published in many scientific journals to be read by interested members of the scientific community.

From time to time, research publications having a similar theme are summarized and published in a review article.  That’s the process that was used to summarize the research that focused on the effect of glyphosate on nutrient uptake and plant diseases.

This review article was published on pages 10375 to 10397 in volume 42 of the Journal of Agriculture and Food Chemistry having a publishing date of October 24, 2012.  The review article is entitled: “Glyphosate Effects on Plant Mineral Nutrition, Crop Rhizosphere Biota and Disease in Glyphosate Resistant Crops”.  Authors are: Stephen O. Duke,   John Lyndon, William Koskinen, Thomas Moorman, Rufus Cheney, and Raymond Hammerschmitt.  All are highly respected scientists in a variety of disciplines.  To prepare the review article, the scientists summarized information which appeared in 232 peer reviewed scientific articles.

I do no intend in this blog to provide a detailed description of the review.  The summary provided by the authors is appropriate.  They state: “Claims have been made recently that glyphosate resistant (GR) crops sometimes have increased mineral deficiencies and plant disease.  Our conclusions are: 1) although there is conflicting literature on  the effects of glyphosate on mineral nutrition of GR crops, most of the literature indicates that mineral nutrition of GR crops is not affected by either the GR trait or the application of glyphosate; 2) most of the available data support the view that neither the GR transgene nor glyphosate use in GR crops increases crop disease; and 3) yield data on GR crops do not support the hypothesis that there are substantive mineral nutrition or plant disease problems that are specific to GR crops.”

The message delivered in this summary is clear.  A large amount of scientific research has shown that use of GR resistant corn and soybeans has not had any negative effect on nutrient uptake and plant diseases.  Those who take the opposite view are basing comments on emotion and perception– not science.  It’s time to ignore this minor distraction and move forward to more efficient and profitable crop production.



Discovery  Farms-Minnesota is a farmer led initiative organized to gather water quality information from a variety of farm enterprises and landscapes across Minnesota.  One of the major objectives of the farmer supported program is to collect water quality information under real world conditions and provide practical, credible, and farm specific information to support better farm management decisions.  For most farms, water quality measurements are taken at the edge of the field.  Farms selected for the initiative are thought to be representative of the diversity of farm enterprises and soils in Minnesota.

In Minnesota, the alfalfa crop  is a major component of many livestock enterprises across the state.  This blog provides a progress report of measurements of sediment, nitrogen, and phosphorus movement from an alfalfa field in Goodhue County the southeast part of the state.  The alfalfa is grown for a cow/calf enterprise.  The topography is rolling and the silt loam soils have good internal drainage.  It’s important to point out that information gathered from this field is not representative of all alfalfa fields in Minnesota.  Likewise, the management practices used on this Goodhue County farm are not necessarily identical to those used by other alfalfa producers.  This is one example of farm specific information.

The information is summarized on a water year (October 1 through September 31) basis.  Measurements are made when soils are frozen as well as when soils are not frozen.  The monitored field was established alfalfa in both WY 2011 and WR 2012.  Fertilizer was not applied to the alfalfa.  Four cuttings were harvested each year.

Measured precipitation is summarized in Table 1.  For the two water years (WY2011 and WR 2012), total precipitation was nearly the same; but, there was considerable snow melt in WY2011 producing runoff.  Runoff in WY 2012 was relatively low.  There was very little snow melt and there were no major rainfall events that caused runoff.  The higher runoff in WY 2011 produced more sediment movement.  Smaller amounts of runoff in WR 2012 were associated with lower amounts of sediment.

TABLE 1 – Measured precipitation and associated sediment movement from an alfalfa field in Goodhue County.

14.7.22 Table 1

Sediment loss from the frozen soil (83%) contributed substantially to the higher movement measured in WY 2011.  By Contrast, 31% of the sediment movement in WR 2012 was measured when the soil was frozen.  In both water years, soil loss was exceptionally low.  The values are much lower than “allowable” losses that are part of conservation plans for soils with a silt loam texture, moderate slopes , and good internal drainage.  The data collected from the two water years confirm the general concept that alfalfa reduces sediment movement from the landscape.

For the Discovery Farms project, water samples are analyzed for total phosphorus (P) and soluble phosphorus (P).  Soil test values for P at this site (Bray Test) for 0 to 6 inches were very high (80 ppm).  The amount of P attached to the sediment is determined by subtracting soluble P from total P.  Relatively small amounts of P movement were measured in each water year (Table 2).  Sediment P accounted for 66% of P movement when soils were frozen in WY2011.  In contrast,, 25% of the sediment P was measured when soils were frozen in WY 2012.  In these two water years, movement of sediment bound P was directly related to sediment movement.

TABLE 2 – Phosphorus movement in two water years.

14.07.22 Table 2

Nitrogen is a major consideration when water moves from a field.  For this alfalfa field, water moving over the surface was analyzed for total nitrogen, organic nitrogen, ammonia-nitrogen and nitrite+nitrate nitrogen.  The results are summarized in Table 3.

Because of differences in precipitation each year, nitrogen movement was not consistent.  The higher amount of total nitrogen measured in WY 2011 is attributed to the nitrogen in snow melt on frozen soil.  There was very little snow melt WY 2012 and runoff in rainfall was not a major factor.  Therefore, measurements of total nitrogen in WY 2012 were lower.

The numbers reported in this blog are intended to be a progress report only.  They are measurements from an alfalfa field over a period of two years.  There should be no expectation that the same numbers would apply to all alfalfa fields.  It’s obvious that several factors such as soil texture , precipitation, density of the stand, etc. will affect sediment and nutrient movement in any production environment.

Table 3 – Nitrogen movement from an alfalfa field in Goodhue County

14.07.22 Table 3

However, movement from this alfalfa field could be considered to be low.  It was certainly less than perceived by many.  Further, these values are not intended to be used as standards or goals.

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