SnapPlus is Wisconsin’s nutrient management planning software!

The program helps farmers make the best use of their on-farm nutrients, as well as make informed and justified commercial fertilizer purchases.

By calculating potential soil and phosphorus runoff losses on a field-by-field basis while assisting in the economic planning of manure and fertilizer applications, SnapPlus provides Wisconsin farmers with a tool for protecting soil and water quality.

To watch the video What is SnapPlus?, click on the quick summary and download the PDF for the link!

A qualified nutrient management planner can prepare and sign off on a nutrient management plan.

Qualified planners include:

• Certified Crop Advisors (CCA)
• Certified professional agronomists (CPAg)
• Certified professional soil scientists (CPSS)
• Farmers who successfully complete a DATCP-approved training course (like this one!)

Yes!

Incentives include funding for practices such as soil sampling, planting a cover crop, or purchasing equipment to improve nutrient stewardship.

Check with your local Wisconsin County Land and Water office or NRCS office annually to see what incentives are available.

A Concentrated Animal Feeding Operation (CAFO) is defined as:

Any animal feeding operation with 1,000 animal units or more.

See the Quick Summary for a link to a worksheet where you can calculate animal units (AUs).

SnapPlus is a powerful tool that allows you to use soil test data from your fields to calculate the fertilizer amounts needed based on crop needs and your management decisions using University of Wisconsin data.

Additionally, users can keep track of manure and nutrient applications to make their farms more efficient.

To see all of the how-to videos, click on the quick summary and download the PDF for the link!

Most soils should be sampled every 3-4 years with the exception of sandy soils which should be sampled every 2 years.

Details on how and when to soil sample will be discussed in module S6 Soil Sampling and Procedures.

Nutrient credits are the fertilizer replacement value of non-commercial nutrient resources like manure, biosolids, or legumes. Nutrients from these sources become available over time as the organic materials decompose.

For manure, nutrient amounts can be estimated by referencing the “book” values with the type and amount of manure applied or by having manure tested to determine the actual value. Manure testing is often recommended for liquid manure and manure that is stored for a long period of time or if manure is concentrated.

For biosolids or other soil amendments, the nutrient amounts must be pre-determined by the source or the nutrient content of the material must be assessed by a lab.

For legumes (grown during the previous season), nutrient credits are determined by the legume type, stand density, and previous harvest management.

Using conservation-focused cropping strategies like reducing or eliminating tillage, growing cover crops, planting diverse crop rotations, and/or utilizing rotational grazing can potentially reduce soil erosion, leaching, runoff losses of nutrients, and/or increase soil organic matter.

It is estimated that 1 ton of eroded soil may contain 2 pounds of nitrogen, 9 pounds of phosphorus, 31 pounds of potassium, along with varying amounts of calcium, magnesium, sulfur, micronutrients, and soil organic matter.

Keeping soil in place not only reduces nutrient loss and potential fertilizer needs, but also protects the future productivity of the soil while reducing the risk of nutrients entering surface and groundwater bodies.

Soil organic matter is important to nutrient cycling and retention. Soil organic matter contains nutrients that can become available to plants. It also has a negative charge (CEC) that helps protect certain nutrients from loss from the soil system by leaching or runoff. Using conservation-focused cropping strategies may build soil organic matter content over time, thereby improving nutrient use efficiency and/or reducing supplemental nutrient needs.

For legumes (grown during the previous season), nutrient credits are determined by the legume type, stand density, and previous harvest management.

A nutrient management plan must be made for a pasture if:

• Mechanical applications of nutrients are used
• The average stocking rate is greater than or equal to 1 animal unit/acre
• There is a herd present in the winter (not a feedlot)

DATCP has developed a checklist to let you review your plan and ensure it follow the guidelines for your operation!

This acronym stands for Surface Water Quality Management Area

From line (66) of WI NR243:  

“Surface water quality management areas” or “SWQMA” means all of the following:

(a) The area within 1,000 feet from the ordinary high water mark of navigable waters that consist of a lake, pond or flowage.

(b) The area within 1,000 feet from the high water mark of navigable waters that consist of a glacial pothole lake.

(c) The area within 300 feet from the ordinary high water mark of navigable waters that consist of a river or stream or other non-lake navigable waters.

(d) The area within 300 feet of conduits to navigable waters.

Soil loss tolerance (T) is the maximum amount of soil loss in tons per acre per year, that can be tolerated and still permit a high level of crop productivity to be sustained economically and indefinitely. T values range from 1 to 5 tons per acre per year.

The USDA (1956) defined the following top ten influencing factors of tolerable soil loss for a particular soil:

1. The rate of soil formation from parent material
2. The rate of topsoil formation from subsoil
3. Reduction of crop yield by erosion
4. Soil depth
5. Changes in soil properties favorable for plant growth caused by erosion
6. Loss of plant nutrients by erosion
7. The likelihood of rill and gully formation
8. Sediment deposition problems within a field
9. Sediment delivery from the erosion site
10. The availability of feasible, economic, culturally and socially acceptable, as well as sustainable soil conservation practices.

Soil maps are created for each field using Snap Maps. These maps contain field-specific soil information, including dominate and critical soil series, based on USDA-NRCS information.

Web Soil Survey is a free website hosted by the USDA-Natural Resources Conservation Service where the public can access soils information for almost all locations in the United States. Users can determine the soils mapped within identified field, as well as the associated soil descriptions, soil property, and soil interpretation data for each soil map unit (A link to the Web Soil Survey is listed in the Quick Summary).

Soil texture can be estimated by wetting and ribboning a soil sample. Soil texturing by feel takes practice! A video link on the process can be found in the Quick Summary.

Photo source: https://www.agric.wa.gov.au/soil-constraints/soil-texture-estimating-hand

There are more than 730 (734 as of Nov. 2012) named soils in Wisconsin.

Each one is unique based upon the presence of various horizons, colors, structures, and textures.

The Wisconsin State Soil is Antigo Silt Loam!

A soil’s drainage class indicates the frequency and duration of saturation (soil pores completely filled with water) during soil formation.

Tile drainage or irrigation do not typically influence a soil’s mapped drainage class.

Better drained soils have a greater depth to saturation and therefore, plant roots will typically grow deeper into the soil as compared to more poorly drained soils.

SnapPlus primarily manages nitrogen, phosphorus, and potassium applications, however, other nutrients such as sulfur,
magnesium,
calcium,
boron,
manganese, and zinc
can also be added!

There are 18 essential nutrients for plant growth. These nutrients are divided into two general groups - macronutrients and micronutrients. Macronutrients are needed in greater amounts, as compared to micronutrients, but all are essential for proper plant growth and reproduction.

Plants take up specific inorganic forms of each nutrient. If a nutrient is not found in these specific forms, the plants are unable to take up these nutrients and may become deficient.

Nutrients play specific roles in plant growth and metabolism. The major roles of select nutrients are outlined in the following table.

Plant essential nutrients can be divided into two groups – mobile and immobile – based upon their ability to be translocated within the plant.

Mobile nutrients can be moved to where they are needed within the growing plant. Therefore, deficiencies of mobile nutrients often first appear in the older leaves, as nutrients are translocated to the active growing point.

Generalized diagram showing the portion of the plant where nutrient deficiency symptoms are first observed. Courtesy of the 4R Plant Nutrition Manual, IPNI 2012.

Plant essential nutrients can be divided into two groups – mobile and immobile – based upon their ability to be translocated within the plant.

Immobile nutrients are “locked” in place within plant tissues and cannot be moved to growing plant parts. Therefore, deficiencies of immobile nutrients often first appear in the younger, newly forming leaves.

Generalized diagram showing the portion of the plant where nutrient deficiency symptoms are first observed. Courtesy of the 4R Plant Nutrition Manual, IPNI 2012.

All commercial, manure and by-product nutrient sources should be added into the Nutrients tab.

Nitrogen crediting from legumes is automatically calculated if the legume crop is entered into your crop rotation.

SnapPlus will also calculate how much manure will be available on your farm based on your animal units and your collection methods.

To learn more, download the Quick Summary for links to the following videos:

Nutrient Screen Basics

Entering Manure and Biosolids in the Nutrient Sources Tab on the Nutrient Screen

Entering Fertilizers in the Nutrient Sources Tab on the Nutrient Screen

Estimating Manure Annual Volumes

The nutrient content of soil organic matter varies by its source, as well as stage of decomposition.

In general, 1% soil organic matter contains approximately

1,000 lbs of nitrogen

100 lbs of phosphorus

100 lbs of potassium

plus

secondary macronutrients & micronutrients

It is important to note these nutrients don’t all become available at once. The release of nutrients from soil organic matter in a plant usable form (the process is called mineralization) is controlled by microbial activity and weather, soil and soil organic matter conditions.

Agronomic practices that may lead to increases in soil organic matter include eliminating tillage, reducing soil erosion by wind and water, maintaining living plant cover, growing high residue producing crops, and adding organics, such as manure or compost.

With changes in management, total soil organic matter concentrations may increase slowly over years to decades.

Legumes are plants that produce seeds within pods. Many legume species live in a mutually beneficial (symbiotic) relationship with nitrogen-fixing bacteria, such as Rhizobium.

The nitrogen-fixing bacteria live inside nodules on the legume’s roots, convert atmospheric nitrogen into a plant-available form, and provide some of this nitrogen to the plant.

Forage legumes, such as alfalfa and clover, are often added to livestock diets due to their higher crude protein contents.

Additionally, legumes are commonly grown as cover crops or green manure crops, as the residues may provide nitrogen to other plant species grown in a multi-species mix or to a subsequent crop (known as an N-credit).

Cation exchange capacity (CEC) is an estimate of the soil’s ability to hold onto positively charged elements, such as ammonium, potassium, calcium, and magnesium, dissolved in the soil water. Soils with a high CEC are potentially better able to supply nutrients to a growing crop, as compared to those with a lower CEC. A soil’s CEC is most significantly impacted by the percentage and type of clay within the soil. Soil organic matter also contributes to a soil’s CEC, but its contribution is secondary to the soil’s clay content.

The Nutrient Application planner is a great tool for entering spreading methods for each nutrient source in SnapPlus.

You are allowed to choose unincorporated, incorporated, and subsurface as application type. Banded, starter, and pop-up fertilizer applications should be entered in as a subsurface application.

You are also able to enter lime applications into SnapPlus.

To learn more about how to use the Nutrient Application Planner, download the Quick Summary for a link to the video: Planning Manure and Fertilizer Applications Using the Nutrient Application Planner

Arguably, the easiest way to assess soil compaction throughout a field is to use a soil penetrometer. This tool measures the amount of pressure required to insert a metal rod with a conical tip into the soil profile, also known as penetration resistance. Compact soils require more pressure to insert the penetrometer into the soil profile.

Soil penetrometers often include a color coded, graduated gauge that helps the user assess whether the measured penetration resistance may negatively impact root growth.

In certain field, soil, and weather conditions, placing applied nutrients closer to a plant’s root system may enhance nutrient uptake.

Nutrient placement may beneficially impact root growth when soil pH is outside the ideal range for plant growth, in low and very low testing soils, and in no-till soils, for those nutrients taken up primarily by diffusion (such as P and K), and/or in late-plant conditions.

If fields need lime, SnapPlus will let you know. It will also create a report for spreading lime!

Then all you need to do is call your coop!

Wisconsin, generally soils forming on top of carbonate bedrock.

Soils in the east and south will have higher soil pHs than those forming over the top of igneous rocks (soils in the central and western portions of the state).

Agricultural management practices can have a dramatic impact on soil pH.

Therefore, soil testing is the only way to know the pH of your soil.

Purchased soil testing kits are not sensitive enough to accurately measure soil pH for agronomic situations.

Calculating a soil’s lime need requires the use of a chemical buffer to determine the amount of exchangeable acidity within the soil. A simple soil testing kit cannot be used to determine lime need.

The best and most accurate method is to send properly collected soil samples to a DATCP-approved soil testing laboratory for analysis.

In general, nitrogen fertilizers containing ammonium (e.g. urea, ammonium sulfate, etc) are more acidifying than those containing nitrate (e.g. potassium nitrate, ammonium nitrate, etc).

Phosphorus fertilizers, in general, are less acidifying than nitrogen fertilizers.

Potassium fertilizers typically have little to no impact on soil pH.

See table 4.2 of University of Wisconsin Extension publication A2809, Nutrient Application Guidelines for Field, Vegetable, and Fruit Crops in Wisconsin. Use the link in the Quick Summary to view the publication and the full table.

SnapPlus has a web application called SnapMaps, which uses GIS and let’s you locate and draw your fields’ boundaries.

It is really important that you name your fields on your maps and then be consistent when you submit your soil samples for testing. That way, your results will match-up when you import them back into SnapPlus!

You can also print out your maps and mark them up while you are sampling. That way you have a record of where the samples were taken!

For more information about SnapMaps, click on the quick summary for links to some great how-to videos!

Grid-point sampling is the process that uses global positioning system (GPS) to develop equal size grids and sampling points for a field. To accurately capture nutrient variability throughout the field, the grids are as small as one acre or as large as 2 to 2-1/2 acres. The sample point is identified with geographical coordinates, and 10 cores in a 10-foot area are taken around this point to make a sample.

It is recommended to stagger the sampling points throughout the field to reduce bias in sampling similar areas in the field. Instead of using the soil test results to make a blanket fertilizer application recommendation, grid-point soil test results are used to make variable rate recommendations allowing the nutrients to be applied where they are needed.

Zone sampling is another process that uses technology to determine sampling areas. Zone sampling uses information from yield maps, aerial photographs, or other precision agriculture maps to develop sampling areas that appear similar. Sampling can be done through the traditional soil sampling process or using a grid-point sampling. If grid-point sampling is done and the results show no or little difference between areas, take the average of the sample results to create a general fertilizer recommendation for the field.

Contour strips should be sampled separate if the strip is five acres or more using the traditional soil sampling techniques. If the strips are less than five acres, then the strips can be combined if the cropping and management histories are the same. Grid-point sampling contours may cause unusable soil test results if the grid covers more than one strip and all the cores come from one strip or if cores are taken from the edge of a strip.

Below are guidelines to sampling soil in various tillage practices regardless of if using the traditional, grid-point or zone sampling methods:

Moldboard plow: Sample to the depth of tillage

Chisel plow or offset disk: Sample to ¾ of depth of tillage

Strip till or ridge till: Sample equal number of soil cores from ridges and furrows or the area between the rows. If fertilizer was not banded in the strips or ridges, collect cores at the six inch depth on the ridges. In the furrow, take samples at four inches. Combine the cores to make a composite sample.

No-till: No-tilled fields of over five years may develop an acidic layer at the surface from nitrogen fertilizer applications. This acidic layer may cause triazine herbicides to lose effectiveness. To test the pH, sample at a two inch depth. It is important to note the sample depth on the soil submission form to be tested for pH. A phosphorus and potassium test can be requested to determine if these nutrients are also building up on the soil surface. A six inch sample is still required to determine fertilizer recommendations.

It is important to request your soil test reports from the laboratory in the SnapPlus import format (.csv).

Additionally, you should verify that the field names in your soil test reports match the field names in SnapPlus exactly or you will have errors when importing results. If you had additional soil tests run outside of those considered routine, be sure to review the soil test reports, as you may miss some guidance comments that will not import into SnapPlus.

For more information about SnapMaps, click on the quick summary for links to some great how-to videos!

Micronutrients are required in very small amounts by the crops. In fact, high levels of some micronutrients may become toxic to plants.

Deficiencies of boron, zinc, and manganese are often the most common micronutrient deficiencies experienced by Wisconsin farms.

Farms that apply manure may not experience micronutrient deficiencies, as the manure contains several to all of the micronutrients.

Soil testing:

Currently, Wisconsin has reliable soil tests for boron, manganese, and zinc. Wisconsin also has tests for copper, iron, and molybdenum, but these tests do not provide nutrient recommendations.

Plant analysis:

If the crop is showing deficiency symptoms, a plant analysis is often the best way to determine which micronutrient may be deficient. At times it may be necessary to do a plant analysis to confirm a soil test result of a deficient nutrient.

Pastures need to be included in a nutrient management plan if one or more of the following applies to the farm:

• The pasture receives nutrients such as fertilizer or manure applied by tractor and spreader.
• The pasture has an average of more than one animal unit (1,000 pounds of animal) per acre throughout the grazing season.
• The pasture has a herd present during winter for feeding activities such as bale grazing and the pasture is not considered a feedlot.

Pastures do not have to be included in a nutrient management plan if the pasture does not receive applications of nutrients and one of the below applies:

• The pasture is a feedlot or an area that is considered a barnyard, exercise area, or other area where livestock are concentrated, and vegetation is not maintained for forage.
• The pasture has an average of less than one animal unit per acre throughout the grazing season.

SnapPlus can provide recommendations for various liming materials based on the neutralizing index.

This function is located in the Cropping tab. Click on the “Lime Rec” box where you can add the lime source, the crop year, season, the neutralizing index, and the rate. SnapPlus will calculate whether the lime application has met the lime need or if an additional application will need to be made.

For more information on how SnapPlus can help manage lime applications, click on the quick summary for the link to the Planning and Recording Lime Applications in SnapPlus video!

Lime should be applied and incorporated at least 6 to 12 months prior to planting an acid sensitive crop such as alfalfa.

Application rates for lime should never exceed 12 ton/acre (8 ton/acre for potato).

The minimum application rate is:

• 1 ton/acre on sandy soils with <1% OM
• all other soils 2 ton/acre

Lime recommendations are made using the target pH for the most acid-sensitive crop in a 4-year rotation.

No additional lime should be applied until the most recent application has had 2-3 years to equilibrate with the soil.

While the optimal pH levels vary for each crop, and growers should review pH needs for their specific rotations, on average, most horticultural and agronomic crops grow best in soil pH between 6.0 and 6.8.

SnapPlus can calculate the amount of nutrients applied if you are using liquid fertilizers.

In the Nutrient tab you can add a new liquid fertilizer by clicking on the green plus icon. A new window will pop up, click on “OK.”

This will bring up another window where you can enter the new fertilizer details.

Select “Liquid” and enter the fertilizer name in the text box. Then enter the percent nitrogen (% N), phosphorus (% P2O5), and potassium (% K2O). You can also enter in sulfur (% S), magnesium (%Mg), and/or calcium (% Ca). You will also need to enter the weight of the gallon in the “Density” text box.

You can also choose if there was a nitrate inhibitor (NO3- Inh.) added to the fertilizer.

Once you have this set up you can use the fertilizer when adding nutrients in the “Cropping” tab.

For more information on how SnapPlus can help with nutrient management planning, click on the quick summary to get a link to the SnapPlus How-To Videos channel on YouTube!

Nitrogen is readily available in the ammonium (NH4+) and nitrate (NO3-) forms.

Phosphorus binds quickly to soil particles and only becomes available through the weathering of the soil material or through diffusion.

Potassium is readily available to the plant in the ion form of K+.

There is a wide array of products being sold that claim to be organic.

You must work with your organic certification agency to determine which products are approved to apply to your farm.

To calculate the fertilizer rate, you will need the soil test recommendation and the analysis of the fertilizer you want to apply.

For example, a soil test recommends that an alfalfa field needs 155 pounds of potassium (K20) applied and you would like to use potash (0-0-60).

To determine the amount of potash to apply to the field divide the amount of potassium needed by the fertilizer percent as a decimal. Remember the 60 in the analysis of potash is a percent, so when calculating the amount, you will need to use .6 in the equation.

In this case we would divide 155 by .6 and get 258 pounds of potash to spread. It may be necessary to round to the nearest round number depending on the capabilities of the fertilizer spreader.

If you are planning on using more than one fertilizer to apply one particular nutrient, such as a starter fertilizer followed by a sidedress nitrogen application then there are a couple extra steps. Using the starter and side dress example, A2809 recommends a rate of 105 pounds of nitrogen to be applied to a corn crop. You are planning on using 200 pounds of a 20-10-20 starter fertilizer followed by a side dress application of urea (46-0-0). To determine how much nitrogen you are applying in the starter you will need to multiply 200 by .2, remember fertilizer analysis are percentages and need to be changed to a decimal when doing this math. When you multiply these numbers, you get 40 pounds of nitrogen applied in the starter fertilizer. Take the original recommended amount, 105 pounds, and subtract the 40 pounds being applied with the starter. This will be 65 pounds remaining that the crop needs. Now divide the 65 pounds needed by .46 (the analysis of the urea) and you will get 141 pounds of urea to be spread. Again, you may need to round to nearest round number depending on the spreader capabilities.

Soil organic matter is measured in many soil testing labs by heating the soil well above 1000 degrees F and burning all the organic matter off.

The change in soil weight from pre-burn to post-burn is then used to calculate the percent soil organic matter.

For corn and wheat, SnapPlus uses the Maximum Return to Nitrogen (MRTN) ratios to determine the appropriate nitrogen application rates. For all other crops, nitrogen rates are based on University of Wisconsin recommendations, which are listed in UWEX A2809 Nutrient Application Guidelines for Field, Vegetable, and Fruit Crops in Wisconsin.

Research on nitrogen rates and recommendations is an ongoing process!

The nitrogen cycle displays the process for nitrogen movement and use within the ecosystem.

Microbes help convert nitrogen into usable forms for plant update.

Specifically, nitrogen-fixing bacteria are species which can convert atmospheric nitrogen to nitrate which is then able to be taken up and used by the crop.

Soybean root with healthy Rhizobium bacteria nodules.

Nitrate is NO3-

Ammonium is NH4+

Many nitrogen fixing bacteria can convert other forms of nitrogen into ammonium and nitrate.

The numbers found on a fertilizer label or bag is the percent of product in that material.

For example, urea fertilizer has a fertilizer grade of 46-0-0, which means that it contains 46% nitrogen, 0% phosphorus and 0% potassium.

If you to apply 160 lbs of N per acre, then you need to calculate the amount of urea you would need to apply to get that rate.

Just divide160 (your needed N rate) by 0.46 (46%) and you get the result of 348 lbs urea per acre.

Nitrogen fertilizer guidelines for corn and wheat use a flexible system designed to provide Maximum Return to N (MRTN) based on the cost of N and the anticipated corn price.

SnapPlus planners can enter a N:Corn Price Ratio or keep the default setting. The default setting for both corn and wheat crops is 0.05/MRTN.

The MRTN rate for each field and crop year can be reset from either the Cropping screen or the Rotation Wizard (for multiple fields and years).

For more information about how to change MRTN setting in SnapPlus, click on the quick summary for a link to the how-to video!

Yes, although there are book values that can be used, it is recommended that you submit a sample to determine actual nutrient content of manure.

Samples should be sent to a certified program sampling lab such as the UW-Soils Lab.

See the quick summary for a link to the website.

The Nutrient and Pest Management Program or your local Extension educator can help!

The basic method is to use portable scales to weigh the spreader both empty and with a typical load size. Then calculate a tons per acre spreading rate using field records on how many loads were put on a particular field of known acreage. This rate can be considered the “standard” for a farm, keeping in mind that typical ground speed, PTO speed and spreader settings stay the same.

When using MRTN, the nitrogen fertilizer adjustment for a preceding soybean crop is already reflected in the recommended rates for corn and wheat, so no nitrogen credit is needed.

Changes to nitrogen rates based on soil nitrate tests can quickly be made using the rotation wizard and applying nutrient systems.

For more information about how to use the rotation wizard or nutrient systems in SnapPlus, click on the quick summary for a link to the how-to videos!

Preplant Nitrate Test, (PPNT), assesses nitrate carry-over from the previous growing season and is used to adjust preplant or sidedress N application rates.

A PPNT is most effective when corn follows corn in rotation.

Preplant Nitrate Test (PPNT) assesses nitrate carry-over from the previous growing season and is used to adjust preplant or sidedress N application rates.

A PPNT is most effective when corn follows corn in rotation. A PPNT is used to assess N carry-over in the top three feet of soil if the previous season’s N applications were:

• In excess of crop need,
• Previous growing season and overwinter precipitation was below normal,
• N fertilizer was applied and the crop was
  not planted due to weather conditions (prevent plant), or
• When manure or legumes were not fully credited for the previous growing season.

Due to sample collection in early spring (post-frost, but before planting and any N application), a PPNT does not measure N released from previous fall, winter or spring applications of manures or N released from the mineralization of forage legume residue. If a PPNT is used to adjust a N fertilizer rate, manure should be properly credited using established book values or manure analysis results. Likewise, legume nitrogen credits should be properly credited where appropriate. (See Chapter 9, A2809, Nutrient Application Guidelines for Field, Vegetable, and Fruit Crops in Wisconsin)

When corn follows corn, the PPNT is the preferred soil nitrate test to evaluate potential N carryover into the second growing season
after a manure application or alfalfa crop termination. However, the PPNT does not measure N released during the second growing season after application/termination.Therefore, total N application rates should be adjusted using second-year manure or legume N credits, as well as PPNT results.

The pre-sidedress soil nitrate test measures the amount of nitrate-N in the crop root zone that “carried over” from the previous growing season or has been released from a previous legume crop or manure application.

Residual nitrate that is present in the spring is available to crops for the growing season.

For example using the chart below, if the PSNT result in 13 ppm, that would translate into a 35 lb N/acre credit.

Samples should be taken 1 to 3 weeks after black layer formation.

The end-of-season stalk nitrate test is intended to be a tool to help growers determine if their N management practices were adequate or if adjustments could be made to improve profitability and/or reduce N losses to the environment.

When using MRTN, the nitrogen fertilizer adjustment for a preceding soybean crop is already reflected in the recommended rates for corn and wheat, so no nitrogen credit is needed.

When entering starter fertilizer in SnapPlus, use the subsurface application option. In some crops, an extra 20 lb N and 20 lb P above the recommended rate may be allowed (as in A2809).

For more information about how to change enter starter fertilizers in in SnapPlus, click on the quick summary for links to the how-to videos!

Yes, when applied at the right time. A nitrification inhibitor temporarily delays the conversion of ammonium to nitrate.

Inhibitors are most useful in moderately or well-drained soils that are in areas prone to heavy rainfall or frequent flooding.

If fall nitrogen applications with inhibitors are planned, wait until the soil temperature has dropped below 50 degrees Fahrenheit and the soil is likely to be frozen for most of the winter.

Polymer-coated urea (PCU) is a slow-release nitrogen (N) fertilizer product in which each urea prill is individually coated with polymer (plastic).

PCU benefits are realized when environmental conditions cause substantial N loss, however, damage to the polymer coating can change the release pattern of N during the growing season, decreasing the effectiveness of PCU.

New research and many advances are in progress to advance nitrogen management with new approaches for materials, placements and timings.

Other research includes expanding nutrient use efficiency, new varieties which need less nitrogen, and also looking at new ideas such as hyper-spectral imaging.

Once these approaches are finalized, then growers can continue to adopt these strategies!

In addition to assisting farms manage on-farm and purchased nutrients, SnapPlus also helps farms identify potential management practices leading to impaired surface water quality.

By assessing the calculated P-Index for each field, farms can determine if soil test levels, nutrient additions, and agronomic practices in that field are potentially increasing the risk of phosphorus being transported to local rivers, streams, lakes, or ponds.

Fields with lower P-Indexes are less likely to lose phosphorus to surface water bodies.

For more information about SnapPlus, click on the quick summary for the link to the SnapPlus YourTube channel!

The basic process of eutrophication of Wisconsin freshwaters is

1) Phosphorus leaches or runs off the land surface into water bodies,

2) Phosphorus stimulates algae growth,

3) Algae dies, sinks to the bottom, and is decomposed, and

4) The decomposition process strips oxygen from the water resulting in habitat impairment and death of aquatic life.

While the estimates vary, it is often assumed 300 to 500 lbs of wet algae can be produced for every one pound of phosphorus that reaches a fresh water body (lake, pond, river, or stream).

Phosphorus is lost from natural lands (forests, wetlands, and prairies) to surface water bodies through the movement of dissolved phosphorus from decomposing plant materials and phosphorus attached to eroded soil materials.

While natural lands do lose phosphorus to surface water bodies, the magnitude of loss is often significantly less than from managed agricultural and urban systems.

Phosphorus fixation is a chemical reaction that occurs when dissolved phosphorus (commonly phosphorus applied via fertilizers or manure) reacts with other ions in the soil water to become a solid. Once a solid, the phosphorus is no longer plant available. Solid phosphorus will not become plant available again until the mineral dissolves (which is a slow weathering reaction).

Maintaining a soil pH near 6.5 will help to keep applied phosphorus available for plant uptake.

Penn, Chad, Camberato, James, 2019/06/08. A Critical Review on Soil Chemical Processes that Control How Soil pH Affects Phosphorus Availability to Plants