News

Soil Types and Herbicide Rates

As for many growers across the Midwest, weed control and suppression has been a struggle for 2024.  Due to warm temperatures and high winds some may think twice about relying on their post-emergence application for the following year.  One of the best options, weather willing, is investing more in the pre-emergent rather than one or more post applications.  A crucial part of residual herbicide use is soil type.  Some of the herbicide applied is bound by soil.

Soil types can be categorized by sand, silt, loam and clay etc., but how do these affect herbicide applications?  Many of these categories are a combination of several different soil types.  These are generalized into different soil textures.  For pesticide application, they are separated into four different groups: Coarse, Medium, Fine and Organic.

Coarse soils include sands, loamy sands and sandy loams.  These have a general CEC of 1-5 for light colored soils and 5-10 for dark colored.  Medium soil include sandy clay loams, sandy clays, loams, silt loams and silts.  These have a CEC range of 11-15 for light colored and 15-20 for dark colored soils.  Fine soils include silty clay loams, silty clays, clay loams and clays.  Their CEC range is 20-25+.  Organic soils are most often referred to as peat or muck soils.  The CEC range can be 50-100. 

Textures are important to identify because each texture category corresponds to a different CEC range, or Cation Exchange Capacity.  CEC is the total capacity of a soil to hold exchangeable cations, which is usually included in soil test results.  Since soil is negatively charged, primarily due to clay and organic matter content, certain soils can hold onto more cations than others.  This too means that some soils will hold more herbicide than others.  Below is a chart showing herbicide rates in correspondence to organic matter and soil textures. 

Comparing the coarse, low organic matter soil to the fine, greater than 3% organic matter soil; it requires double the amount of herbicide applied to obtain proper weed control.  If over application occurs in a coarse soil type, too much herbicide is processed in the crop and can cause damage and/or death.  This can also cause movement through leaching, or runoff, to off-target locations.  Over application in a high clay or organic matter soil can potentially cause carryover to the following rotation. 

For more information on the different CEC ranges within textures and how this successful weed control, visit: https://www.canr.msu.edu/news/determining_soil_type_important_for_successful_preemergent_weed_control

“Good” Vs. “Bad” In Season Soil Tests

When diagnosing seasonal crop issues a soil test is often a key piece of information. When using a soil test in this manner it is best to collect a sample from the affected area and then another sample from just beyond the boundary of the affected area. If the issue appears to have various levels of severity, a sample from each of these areas is advisable.

Commonly when the cause of the issue is soil fertility related, the unaffected area, or “good” sample, is also being impacted to a lesser extent. Often in season crop issues related to soil fertility are not isolated and often more than one aspect of the soil test is impacting the plants. Without sampling the unaffected area, it may not be possible to isolate which aspect is ultimately leading to the issue at hand.

If the unaffected area has a low soil test value that is not affecting the crop performance that is equal to, or even lower than to the affected area, not having the “good” sample from the unaffected area could lead to a misdiagnosis. Mismanagement of a given soil test parameter is often not isolated to a small portion of a field and needs to be identified as part of the diagnosis process.

When both affected and unaffected paired samples they are often labeled as “Good” and “Bad”, upon review of the soil test data they would be better described as “Bad” and “Worse”. Understanding of how soil fertility is causing or impacting the crop issue can be missed without paired samples. For more help evaluating the impact of soil fertility from paired diagnostic soil samples, reach out to your Regional ALGL Sales Agronomist.

Selecting the Right Plant Tissue Test Package

All the routine plant analysis packages at A&L Great Lakes Laboratories include the elements, phosphorus, potassium, magnesium, calcium, sulfur, sodium, iron, aluminum, manganese, boron, copper, and zinc. The only difference between the packages is the type of nitrogen analysis that is included.

The P1 package does not include any nitrogen analysis. All the other nutrients are included because they are all collected with the same laboratory process. This package is generally used for research and field trials where nitrogen is not a variable.

The P2 package is the standard for all row crops and most specialty crops. This package includes total nitrogen. The nitrogen sufficiency status for nearly all crops is based on total nitrogen.

The P5 package includes nitrate analysis. Nitrate is the mobile form of nitrogen in most plants. So, when analyzing entire leaves, the concentration is generally very low. The nitrate analysis is only appropriate for very few crops and plant parts, primarily potato and tomato petioles. The concept is to capture the fraction of nitrogen that is moving between the leaves and stems so that fertilizer inputs can be adjusted in highly managed specialty crops. For most crops there are no sufficiency ratings for nitrate levels. For that reason, when routine row crop samples are submitted to the lab requesting the P5 analysis, the package will usually be changed to P2.

The P6 package includes both the total nitrogen and nitrate. Again, this package is intended to be used for the same crops as the P5 package. However, any plant submitted requesting the P6 package will receive it since it contains the total nitrogen that will provide sufficiency ratings.

For routine plant tissue testing, the nitrate levels really do not provide any useful information and are often below the minimum reporting limit. The P2 package is the appropriate package 99% of the time. If you are working with a new crop or have questions regarding plant tissue sampling, contact your ALGL agronomist.

Sampling Hay for Feed Analysis

Proper feed analysis is crucial for maintaining the health and productivity of livestock.  Accurate sampling of hay and forage is the first step in obtaining reliable feed analysis results.  This article outlines the best practices for sampling hay and forage to ensure that the samples accurately represent the feed being used.

Sampling hay and forage is essential for several reasons.  Knowing the nutritional content helps formulate balanced diets.  This ensures the animals receive all the essential vitamins and minerals required.  Feed analysis can prevent overfeeding or underfeeding, and in turn will optimize feed costs.  Sampling can also identify potential deficiencies or toxicities in the forage, preventing health issues in livestock.

According to the A&L Great Lakes Laboratories Agricultural Feed Analysis Sampling Guide 

Hay may be sampled as it is stored, if it is dry enough to keep without further curing. Different cuttings should be sampled and analyzed separately unless different cuttings are being fed at the same time, in which case they may be sampled in the same proportions as they are being fed.

 Hay samples should be taken with a core sampler, if possible.

1. Ensure that tips are sharp enough to cut through the hay to prevent selective sampling.
2. Core sampler should penetrate at least 12”‐18” into the bale.
3. If using an electric drill or a hand brace, run the drill at slow speeds. High speeds heat the probe and can damage supplies.
4. At least 12 cores of hay should be taken from random bales or locations if loose or chopped hay.

When sampling hay to be fed on your farm, avoid sampling decayed or moldy hay or other portions of hay that will be discarded or would likely be refused when fed to animals’ free choice. However, include deteriorated materials if the hay will be ground, sold, or purchased in order to best describe all the hay. Place the entire sample into a plastic bag and seal tightly.

 To sample square or round bales, collect one sample from each 15-20 bales (from a single lot).  The core sample must be pulled from the end of the bale with the core puller inserted in the center.  If these are round bales, take the sample from the wrapped circumference and not the open ends.  By doing this, on both types of bales, the sample will include the most layers and provide the best results.

For additional information about sampling pastures, loose or compressed hay and forage visit the Feed Analysis page on the A&L Great Lakes Laboratories website.  There the sample guide, pricing submittal form and a sample report will be located. 

Converting ppm to Percent

In fertilizer, compost, manure, and plant tissue samples both ppm and percent (%) data values are common. But how do they compare?

1% = 1 part/100 parts = 10,000 parts per 1,000,000 parts.

Both are units of concentration, just very different in magnitude. 10,000 ppm is the same as 1%. For larger concentrations % is commonly used to keep from reporting very large ppm numbers. With lower concentrations ppm is commonly used to avoid very small fractions of %. The reporting of nutrients in large ppm values is common on environmental reports for the analysis of biosolids.

The scale of the two units can be confusing. For example, a liquid fertilizer sample came to the lab for analysis and the results from total nitrogen was 0.14%. The customer called the lab concerned with such a small number. The customer had used test strips to do a rough estimation of the plant available nitrogen in the material. The material exceeded the maximum of test strips leading to a plant available nitrogen concentration of at least 500 ppm, how could the lab result be less than 1% total nitrogen? The 0.14% lab result was equal to 1,400 ppm total nitrogen.

Moss in Lawns

There are many rumors and common beliefs about the impacts of soil fertility and the presence of moss in lawns. Many believe that the moss grows as a result of a nutrient “imbalance” or an acidic pH. In reality, soil fertility is a relatively minor factor when it comes to moss.

In a well-maintained lawn, the grass is generally able to outcompete moss. When the grass is struggling to grow, it opens the opportunity for moss and other weeds to establish. However, soil fertility is not usually the cause of a struggling lawn when moss takes over. The physical condition of the soil and the environment tend to promote moss growth. Mosses thrive in shaded, moist areas. Soils that sit wet also tend to be compacted. Grass struggles in these conditions.

If you are dealing with moss in your own lawn or are a service provider with clients with moss issues, there are options, but they are generally not simple or cheap. In the short term, mosses are very easy to kill. There are several commercial products available at home and garden stores to kill moss. There are many homemade solutions that can be found with a quick internet search, though there is no guarantee they work. Moss can even be removed by raking since it has very shallow roots. However, it will just come back if the physical soil conditions and environment are not improved to promote grass growth. The most cost-effective option is to aerate the soil. This will help loosen compacted soil and improve internal drainage. If the area is heavily shaded, consider pruning trees to increase solar exposure to the lawn. The most effective option, but also the most expensive, is to install subsurface drainage to remove excess water from the area.

Once the soil conditions have been improved, now is the time to take a soil sample and address any fertility problems that might be holding your lawn back.

Challenging Conditions and Nitrogen Timing

Depending on each farm’s source for fertilizer recommendations, and crop requirements, each crop is going to need a certain amount of nitrogen.  In this example, corn will be the crop of focus.  Once again most of the Midwest Corn States have been experiencing an unfavorable, wet spring for 2024.  This has led to many challenges, and applying a pre-nitrogen application is not an exception.

                Even though most fieldwork has been on standby, today’s modern farming technology allows growers to remain agile.  For most, the understanding of dispersing risks of applying all, or most, of their crop’s fertilizer needs throughout the growing season is self-explanatory.  What happens if one of the applications is missed due to poor weather?  Split applications greatly reduce this risk and can be made up elsewhere.

                The top priority, being good stewards of the land, are implementing the 4Rs.  These Rs stand for: right rate, right source, right placement, and right time.  Even though some will apply certain nitrogen products in the fall, or early spring, keeping the nitrogen application as close to or during the growing season is always the right choice.  This best utilizes the farmer’s inputs and can lower application rates.  There are many different approaches to obtaining full season application rates while missing, in this example, a pre-nitrogen application due to challenging weather conditions.

                The first situation would allow for fertilizer application while seeding.  For corn this is generally through an in-furrow tube, off-set incorporation (2x2), dribble tubes, or other types of liquid injection (dry fertilizer in other parts of the world).  In-furrow tube options can range from application directly on, under or between the seed.  While this is great for starter applications such as 6-24-6 or 10-34-0, they are not able to apply high enough nitrogen amounts without causing significant injury to the germinating seed.  Dribble tubes are usually placed toward the rear of the row unit on the planter.  This is because anything placed in front, or midway, can splash product on the unit causing corrosion and premature failure to any unprotected metal or electrical components.  They are the cheapest option for fertilizer applications on the planter, but dribble tubes do not obtain the right placement. 

Off-set incorporation needs to be a rather broad category.  This is utilizing a knife, coulter, or disc to open a channel at any given distance from the seed furrow and placed below the soil surface.  For planter options, this gives the ability to use higher rates since it is not located as close to the seed.  2x2 is amongst the most popular setups.  The channel is placed two inches to the side of the seed and two inches below the seed furrow.  There are many different options for distances and depths, but for the planter pass to be the first fertilizer application of the year a 2x2x2 option is growing in popularity.  These setups are placed on both sides of the furrow and can allow for 60-80 units of nitrogen in a single pass while seeding.

This is just one pass to a fertilizer management plan.  To obtain the season’s total nitrogen needed, for growing a corn crop, in-season passes will need to be conducted.  This may include nitrogen sidedress applications, and potentially multiple times, or the use of a high-clearance system.  It is important to always incorporate nitrogen applications.  If the nitrogen is left on the surface, or unprotected, it has a greater risk of volatilization before it can be made accessible to the plant’s roots. 

Applying Pelletized Lime at Planting

While pelletized lime reacts faster than standard ag lime, it does have its limitations. It takes 3-5 months for pelletized lime to reach maximum adjustment of soil pH. The key difference between pelletized lime and standard ag lime is finless of grind. Pelletized lime is standard ag lime that has been ground to a much finer and uniform particle size that solubilizes and reacts quicker. The material is then pelletized using a binding agent to make a more application flexible product.

If the goal is to make small annual applications for pelletized lime to maintain pH over time, the timing of the repeated application of not an issue. If the goal is to correct a very low soil pH to reduce impact on the next cropping season, timing of application is very important.

Pelletized lime works very well when applied in the fall resulting in a notable soil pH increase by spring planting that should carry though the growing season. The closer to planting the material is applied, the less impactful it is soil pH increase in that growing season. Very early spring applications will have a significant impact on soil pH mid growing season. Applications made at planting will have a significant impact on soil pH during reproduction and grain fill. 

Pelletized lime applied in the fall, in combination with fall application of standard ag lime, is a very effective way to increase and hold soil pH relatively quickly. The pelletized lime will react and have a significant impact on soil pH the following growing season starting sometime in the spring. The pelletized lime will maintain an elevated pH until the standard ag lime reaches peak pH adjustment 12-24 months after application.

Double Crop Soybean Management

As we are planting our full season soybeans, it is also time to start planning for double crop soybeans. Historically double crop soybeans after winter wheat were not encouraged north of I-70. In recent years reports are growing of successful double crop soybeans as far north as U.S. Hwy 30.  While many are familiar with some of the basic management suggestions for double crop beans, the fertility implications of the beans are often overlooked.

The key to double crop soybean yields is to get the crop off to a strong start as early as possible. To do this cut your wheat as early as possible. If there is the ability to dry the grain or grain moisture discounts are not prohibitive, consider cutting wheat at a higher grain moisture. Baling the straw is often a question of debate and most often is based on the ability to manage/handle residue at planting. Uniform seed depth and seed to soil contact is much more important in double crop beans due to the reduced likelihood of steady rains to overcome planting errors. In the event of heavy rain near double crop planting time, be sure to have good soil conditions for planting. A day or 2 earlier planting will not overcome the negative impacts of planting too wet.  There have been reports of increased yield by cutting the wheat low when baling, the shorter straw reduces shading of small soybeans and reduces water transpiration rates out of the soil through the standing straw.

Large acres of double crop soybeans can be challenging to harvest as you move north. Planting soybean varieties near the top end of the suitable maturity is advisable to maximize yield. This means the soybeans will be harvested late, often in the late fall when drying conditions are not conducive to soybean harvesting. Focus on those fields with better fertility. Good phosphorus levels will promote good root development to help access moisture and nutrients in the drier months of the summer. Good potassium levels will help the soybean plant better utilize water in the hot/dry summer months.

Fertility is often the most overlooked aspect of double crop beans. While often the focus is on the nutrient removal of the wheat straw, a strong double crop soybean crop will remove a significant amount of potassium. Be sure to take the straw and the double crop beans into the crop removal consideration when determining nutrient recommendations.

Figure 1. Nutrient removal amounts and associated cost when baling straw.

What is ENR?

ENR stands for Estimated Nitrogen Release. This is a calculated estimation of how much potential nitrogen may be released from soil organic matter (SOM) in one year. The actual amount and time of nitrogen release is dependent on the composition of the organic matter, soil moisture, and weather.

ENR is a calculation from the soil organic matter value on a soil test. Soil organic matter is reported as the percent of organic matter by weight. ENR is a calculation that is based on a couple of basic concepts regarding soil and the composition of soil organic matter. While these concepts are rooted in scientific research, they can vary.

The first concept explains that an acre of soil weighs approximately 2 million pounds. This is a rough estimation of the soil weight that is tilled/turned when an acre is plowed to the depth of a “standard” moldboard plow, which is assumed to be 6 2/3 inches. Using this standard value of 2,000,000 pounds per acre, we can approximate the amount of soil organic matter in an acre of soil, based on the percent of organic matter found through a soil test. For example, if a soil has an organic matter level of 3%, we can use the 2,000,000 pounds per acre value for the weight of the soil to calculate the total amount of soil organic matter per acre:

2,000,000 x (3/100) = 60,000 pounds of soil organic matter

The second concept states OM is approximately 5% nitrogen by weight. This may vary slightly based on several factors including soil type, management, and composition of the soil organic matter. From our previous example using soil with a 3% organic matter level:

2,000,000 x (3/100) = 60,000 pounds of soil organic matter (SOM)

60,000 pounds SOM x (5/100) =  3,000 pounds of N/acre

While this seems like an impressive value, unfortunately not all the nitrogen is available to the growing crop in a given year. The release of nitrogen from soil organic matter, a process referred to as mineralization, is a biological process that is facilitated by microorganisms within the soil. These microorganisms break down soil organic matter and, in the process, release nitrogen (along with other nutrients) into the soil solution where they can be utilized by the crop. However, the rate of mineralization is not particularly fast, and is governed by many factors. This makes it quite variable year to year. Therefore, it is assumed that only 2 to 4% of the nitrogen in OM will become available in any given year. From our previous example:

2,000,000 x (3/100) = 60,000 pounds of soil organic matter (SOM)

60,000 pounds SOM x (5/100) =  3,000 pounds of N/acre

3,000 pounds N/acre x (2/100) = 60 pounds available N

3,000 pounds N/acre x (4/100) = 120 pounds available N

60-120 pounds available N / acre

 Weather conditions that promote strong plant growth, such as warm temperatures and adequate soil moisture, are also beneficial in the conversion of SOM to plant available nitrogen. Therefore, in those cropping years where weather conditions favor strong yields, they also tend to favor higher mineralization rates. These factors cause greater releases of N from soil organic matter. This greater rate of N release can therefore serve as a kind of buffer, supplying more N to a crop that could essentially benefit from higher nitrogen rates.

Determining a nitrogen application rate that is economically and agronomically optimum can be challenging when the soil has a higher OM content. For example, the nitrogen release from organic matter in a field with 6% OM can range from 120 pounds/acre to 240 pounds/acre. The variation of the nitrogen released is often weather dependent during the growing season and causes challenge when determining nitrogen application rates.

Note - Organic soils, those with greater than 20% SOM, were able to develop over time due to reduced SOM decomposition. Saturated soil conditions for a portion of the year slows SOM decomposition in organic soils, thus reducing the mineralization of nitrogen. Those organic soils that have artificial drainage may experience a higher ENR than those that are not drained, but at a level less than determined by the ENR calculation.