Crop sulfur fertilizer choices

Written by Dr. Paul Tracy on .

Last month, I discussed why we are seeing increased demand for crop sulfur fertilization. The four main reasons are 1) higher crop yields; 2) depleted soil organic matter; 3) lower amounts in atmospheric deposition; 4) less sulfur contained as impurities within modern fertilizers and crop protection products.
The increased demand for sulfur is undeniable. This demand has stimulated numerous new products, new marketing campaigns and new “expertise” on how to address crop sulfur fertilization programs.

{gallery}Nov10/chart:210:270:1:2{/gallery}MFA’s sulfur message has been consistent for many years. Our soil test recommendations for sulfur are aggressive and based upon a combination of targeted crop yield, soil organic matter and soil texture. We know that sulfur pathways through the soil/plant/air/water environment are extremely dynamic. I often compare sulfur’s dynamics to those associated with nitrogen. In fact, since both nutrients are basic building blocks of amino acids and proteins, they are closely related in terms of biological pathways and fertilization requirements. In general, the nitrogen-to-sulfur ratio in soils, plants, animals and organic residues is relatively constant at approximately 10:1. A rule of thumb concerning sulfur fertilization is to apply one pound of sulfur for every 10 pounds of nitrogen. How many crop producers in our region adhere to this ratio rule?
Sulfur fertilizers generally come in two major chemical forms, sulfate (or sulfate derivatives) and elemental sulfur. Organic waste products can also contain a fair amount of sulfur, but their consistency, analysis and nutrient availability is extremely variable. The nearby table lists the major sulfur fertilizer compounds used in our region.

Plant roots can only adsorb sulfur when it occurs in the sulfate form. This leads to a dilemma when choosing the appropriate fertilizer material.

Elemental and organic sources of sulfur must go through microbial-driven processes that convert them into sulfate. This conversion is moisture, time and temperature dependent, and can take from a few weeks to several months.

Sulfate-containing materials provide an immediate plant available form. However, since sulfate is water soluble and soil mobile, it can leach below the root zone with rainfall and irrigation events, and thus become unavailable to the growing crop.

We recommend sulfate-containing materials be applied near planting, as starter fertilizers or even post-emergent. These timings give us the best opportunity for crop uptake before leaching losses can occur.
The time delay for elemental sulfur to convert to plant available sulfate makes it an optimal product for fall or winter applications in front of a summer crop like corn or soybeans. It works extremely well when applied off-season with phosphorus and potassium fertilizers. If elemental sulfur must be applied near planting, a slightly higher rate is recommended.

Conversely, when sulfur response needs are immediate (at spring green-up for fescue and wheat, near planting, as a planting starter or post emergent with corn, soybeans or alfalfa), then the sulfate sulfur form is preferred.

Most sulfur products that contain micronutrients are applied in rates sufficient to satisfy crop micronutrient needs. Since these rates generally account for an extremely small amount of the crop sulfur needs and are relatively expensive.

An example of a new type of sulfur product that attempts to eliminate timing as a major factor is the MicroEssential line from The Mosaic Company. These materials contain half the sulfur as elemental, and half the sulfur as sulfate. They also conveniently place sulfur within phosphorus fertilizer granules to help obtain a more unified material spread pattern.

I expect that we’ll see many more attempts to create sulfur products that reduce the timing risk of the current materials used. As these products enter the market, please evaluate them for consistency, efficiency and compatibility.

Dr. Paul Tracy is director of agronomy for MFA Incorporated.

A better way to fertilize

Written by Dale Guss on .

Recently, I compiled soil test data that came through MFA's West Central AGRIServices office in Adrian from 2000 to present. The first set of tests were from 2000 through 2006. The second were from 2007 through 2009. When I looked at soil tests in the "low" to "very low" range, the results in the older data group showed 52 percent were low on phosphorous and 18 percent were low on potassium.

The later group showed that 51 percent were low on phosphorous and 27 were low on potassium. As for soil pH, the older set of samples showed 29 below a pH level 6. In the more recent collection, some 38 percent of samples were below a pH level of 6. Our MFA home-office agronomy staff agrees that this is not just a local trend in our area, they are seeing this all across the MFA trade territory.

I'm sure that by now you are thinking that this is a fertilizer sales pitch, but that is not my goal. My goal is to develop a fertilizer recommendation based on all information available to us. The only true way to do this is based on current sampling, taken in an unbiased and random pattern and combined with yield data from each field.

{gallery}Nov10/maps:210:270:1:2{/gallery}The majority of combines running now have yield monitors in them, and I would like you to think about what that monitor is showing while you move through the field. In my limited time spent in a combine, I have yet to see a yield monitor display a constant number. It is always moving around, and sometimes by a pretty good percentage. As this is going on, you are looking at the crop in front of you searching for the cause.

Sometimes you see the thin stand, or an area that is always wet. Or, you may be on the thin ground from which you borrowed to fill a ditch or build terraces. Often times, though, you are in the good dirt—maybe where the beans used to be 5 or 10 bushel better, or the corn is the same as it was years ago. You think about the cause, and consider insects or a disease. You know you are fertilizing the same as always, and you are using the best genetics. Still your yields just barely improve.

We all know that most fields have inconsistent soil types and yield capabilities. So could it be that most areas of the field have shown a slight yield increase as you bring a better genetic package with your seed purchase. Meanwhile, it could be that the very best soil yields the same because the fertility has fallen off. In an attempt to increase yields we put on more fertilizer, and as we would expect, slowly the yields increase. But, if you identify the low-soil-test areas, especially the ones that happen to be the best ground and fertilize it to its highest potential, you'll be giving those seed genetics the means to perform as expected.

Now, just like the effect of a few drowned-out spots that drag your average yield, you can see it the other way around with your best soil boosting yield to its potential. I illustrate this to point out that as we continue to plant better genetics and expect more yield from every acre, the fact is our soil fertility is not keeping up with demand. All of the new technology you put in a tractor cab (yield monitors, auto steer and even Internet on your smartphone) may or may not make you money, but my read on the data is that we are neglecting the proven technology available to put each fertilizer dollar in the most needed spot.

We don't always need to crank up the fertilizer rate to get the best return; we just need to apply it wisely. I would like to suggest that you soil test your fields in a grid-sample method and use variable-rate application to apply your fertilizer and lime.

Doing this will place the right amount of fertilizer where it is needed most and not waste fertilizer in places that don't need it.

Dale Guss is the branch manager of MFA-owned West Central AGRIServices in Adrian, Mo.


Crop needs for secondary and micro nutrients are increasing

Written by Dr. Paul Tracy on .

Over the past few years, we have seen an increase in crop deficiencies for the big three (macro) nutrients-nitrogen, phosphorus and potassium. Reasons for those deficiencies have been a combination of high replacement costs and excellent crop yields that have increased nutrient removal. We have been pulling nutrients from the soil fertility bank account that took decades to build. That account is now depleted to the point that crop yields are suffering. Now that prices have stabilized, we are poised to reinvest in the temporarily stressed soil bank account.

As we shore-up traditional fertilizer programs, it is time to pay attention to the full spectrum of crop nutritional needs.

We generally refer to magnesium, calcium and sulfur as the secondary nutrients. They are described as secondary because they are needed in similar amounts as the macro nutrients, but their supplementation has been required less often because of adequate amounts supplied via the soil, atmosphere, other fertilizers, manures and agriculture limestone.

Ten steps to top forage production

Written by Dr. Paul Tracy on .

You can plan your way to better pasture and hay

Step 1: Natural resource inventory

Anyone who reads this column on a regular basis knows the importance that I place on building forage systems around the natural resources present on your farm/ranch. This should be the starting point for all forage production decisions.

A good place to start is soil type information that can be obtained from the Natural Resources Conservation Service. In fact, they have a “Pasture and Hayland Suitability Group” rating and an estimated yield production potential designation for each soil type.

Other natural resources to consider are hydrologic information, topography, non-forage vegetation and wildlife. There are numerous print and electronic resources available to obtain most of this information including the Natural Resources Conservation Service, Missouri CARES, and MFA’s Precision Agronomy Services.

Step 2: Current livestock inventory

Obviously, you should always know your current livestock inventory. Is it enough to meet your financial needs? Are you tracking, sourcing and verifying animals in a way helpful for planning future forage production needs? What are your current animal and forage levels? Do you need increased forage production to maintain the current animal numbers present? Generally speaking, improving forage production efficiency will decrease other inputs, stabilize winter feeding requirements and provide options for increasing animal numbers.

Step 3: Current forage species inventory

Each and every field needs a complete inventory of the forage species, weeds, brush, sprouts and trees present. This should be used as the starting point for maintenance, renovation or re-establishment of any species. Species inventory should be used in developing yield goals, total forage supplying capacity, grazing and harvest strategies and field modification prioritization.

Step 4: Future livestock goals

Before renovation or pasture improvement activities are initiated, future livestock goals need to be determined. In many cases, perennial forage establishment can take a few years to reach optimum production. A flexible five-year plan is usually about as far out as can be maintained. Not only do future livestock needs affect today’s renovation decisions, but they can also affect crop rotation sequences, especially if a kill-smother-kill renovation program using annual smother crops is required. I always emphasize targeting slightly higher goals compared to estimated on-farm forage needs. Extra forage can always be stored for future needs or sold. The 2009/10 year offers a prime example of the need to overestimate winter forage requirements. We went into last winter thinking we had more than adequate hay/silage supplies only to come up short long before spring greenup.

Step 5: Develop an accurate set of equipment needs

It is important to monitor the forage production capital needs of your operation. Careful planning of the vehicle, haying equipment, tractors, planters, storage, fencing, and watering requirements of your operation is very valuable. With the exception of a few rotational grazing purest programs, I am a firm believer in hay/silage production being a key component of any operation that utilizes on-farm forages.

One helpful hint is to try to estimate all farm supply, equipment and maintenance costs on a per acre basis. This is a real eye-opening exercise that will help prioritize forage production decisions.

Step 6: Forage species selection

This can be one of the toughest, yet most important components of a quality forage program. You have choices of perennials vs. annuals, grasses vs. legumes, warm season vs. cool season species, mixed stands vs. monocultures. My advice to growers is to use any and all of the above combinations based upon your needs, experiences and personal preferences. I firmly believe that planned diversity (either within field or between fields) is what separates the great forage producers from the good forage producers. To make the most out of your land resource base, try to diversify forage type or forage uses to stretch the grazing season to as many months as possible. An example of this is to pull animals off of tall fescue in the summer and put them on a warm season grass until as late in the fall as possible. The “rested” fescue fields can then be conditioned and fertilized properly in August to provide an excellent stockpiled forage resource base.

Step 7: Forage crop nutrition management

Crop nutrition is a critical component of any forage system. Hay removes much more nutrients than does pasture. Cool season crops require a different fertilizer application timing than do warm season crops. Soil pH adjustments vary appreciably among forage crops.

All forage nutrition programs should start with soil testing. Soil test recommendations are uniquely designed to address specific forage species needs. For multiple use fields, it is a very good idea to annually rotate hay fields and pasture fields. This will allow the animals to naturally redistribute nutrients across your farm/ranch.

Step 8: Forage integrated pest management

Many folks don’t feel forages require the pest control intensity compared to their row crop counterparts. In reality, weeds, insects and diseases cause millions of dollars in lost forage production across our region annually. Eliminating weed, brush and sprout competition in pastures alone can increase forage and beef production by over 50 percent. Insect control in high value hay crops like alfalfa saves millions of dollars in lost revenue annually. Disease control in forages is more preventative (variety selection) than reactionary (fungicide treatments). For example, WL Alfalfas offer a tremendous disease resistance package compared most other alfalfa varieties. In our environment, a good disease package often provides at least two years extended stand life.

Step 9: Forage harvest management

Harvest management plays a critical role in forage production, quality and persistence. With almost all forages, quality declines as the crop matures. For instance, tall fescue harvested in April/May will contain several percent higher protein content and 25 to 50 percent higher relative feed value compared to fescue harvested in June, July or August. Weather plays an important role in when crops can be harvested, but planned options like bagging the first cutting and species/harvest diversity limiting the total number of acres needed to be harvested at any one time goes a long way toward efficient harvest management.

Step 10: Farm record keeping

Keeping accurate records of all livestock activities is extremely important. Forage production is no exception. All inputs should be carefully recorded and tracked. I am not an economist, but estimating the cost per unit yield produced (hay, silage, beef, milt, etc.) should be recorded as accurate as possible. Keeping a record and budget can help tremendously when evaluating inputs to be made concerning all phases of future forage production management decisions.

I have provided a brief overview of a ten-step forage systems program. Each step contains hundreds of options, and only you can decide which are best for your location. The steps are not necessarily chronological and are certainly not mutually exclusive. In reality, they are completely intertwined and inseparable from each other. As always, best wishes in developing the best forage system possible, and don’t hesitate to contact us with questions, concerns or comment

Dr. Paul Tracy is director of agronomy for MFA Incorporated.

The 4 Rs of crop nutrition—the Right place

Written by Dr. Paul Tracy on .

The final installment in the 4 Rs series

Fertilizer placement can be discussed at two levels. The macro level involves placement based on in-field geographical locations. The micro level is based upon placement within the soil profile and in proximity to the growing crop.

There is no doubt that placing plant nutrients in the Right place on the landscape is one of the most cost effective management strategies. We have been variably applying nutrients across fields for over 15 years. The success of these programs has been tremendous, and I highly recommend the technology across most farming operations.

In terms of micro placement, there is no universal most efficient location. Agronomically, there are multiple factors when considering where to place crop nutrients.

The crop grown has a tremendous effect on plant food placement. With perennial crops like alfalfa and tall fescue, it is impractical to incorporate plant foods, so surface broadcast is appropriate. The one exception is immediately before crop establishment. Whenever possible, lime and fertilizer applications designed to raise soils to optimum levels should be followed by an incorporating tillage immediately prior to planting.

In row crops, there is tremendous diversity in terms of the most effective nutrient placement. We generally recommend completely different fertilizer nutrient placement strategies between corn and soybeans.

Corn has a fibrous root system that extracts nutrients differently than soybeans, which have a taproot system. Corn also tends to be planted earlier than soybeans, a time when cool/wet conditions slow soil nutrient release via mineralization or dissolution, and also slow root growth and subsequent interception of soil derived nutrients. For these reasons, corn responds more consistently to banded fertilizer than do soybeans.

Fertilizer bands tend to be more efficient than broadcast applications in no-till situations. Surface bands concentrate nutrients, thus leading to less potential tie-up on crop residues. Subsurface bands place nutrients deeper in the soil profile where it may be more accessible to plant roots, especially when dry conditions lead to restricted root activity near the surface.

Another practical reason for banding in corn compared to soybeans is the row widths involved. A general rule is that the bands can be spaced no more than two row widths apart. Corn is generally planted in wider rows than soybeans, thus making the equipment set-up, cost and application efficiencies for banding more economical.

Banded fertilizer is generally more efficient in low-testing compared to high-testing soils. This is because the higher concentration of fertilizer in the banded area slows the rate of fixation (tie-up) the soil has for the applied nutrients. Whereas, when soils already contain optimum nutrient levels, our fertilizer recommendations are based upon current crop removal replacement rates and the current season nutrient use efficiencies are not as crucial. It should be noted that banding fertilizer to improve efficiencies in low testing soils is almost always less effective and less economical than maintaining optimum soil nutrient test levels throughout the root zone.

Starter fertilizers are usually placed near the planted seed. This is because under cool-wet early growing season conditions, root growth to intercept banded nutrients and availability of soil nutrients is inhibited.

There are limits to the amount of fertilizer that can be placed near newly planted seed. Fertilizer salts and ammonia injury can occur in pop-up or in-furrow starter fertilizer systems. Therefore, the rule of thumb is no more than ten pounds of combined nitrogen, sulfur and potassium can be applied in-furrow.

I prefer that starter fertilizers be placed at least 2 inches beside and 2 inches below the planted seed. This safely allows much higher rates of nutrients and a more dependable rate for stimulating early season crop growth.

One placement system that is gaining attention is to apply anhydrous ammonia, phosphorus, potassium and desired micronutrients in a band sometime between the fall and early spring. Using RTK guidance, the planted row can be placed directly over the band, therefore obtaining a “starter effect.” These systems have worked well in reduced tillage, strip-tillage or intensive tillage systems.

This ends the series on the 4Rs of crop nutrient management. For more information on the 4Rs, visit the International Plant Nutrient Institute website at

Dr. Paul Tracy is director of agronomy for MFA Incorporated.


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