Nutrient Tracking Tool (NTT)

General

What is NTT?

The Nutrient Tracking Tool (NTT) is a free, online, user-friendly tool that quantitatively estimates the nitrogen, phosphorus and sediment losses from crop and pasture lands. It has been developed by the Texas Institute for Applied Environmental Research (TIAER) at Tarleton State University in cooperation with USDA’s Office of Environmental Markets (OCE), Natural Resource Conservation Service (NRCS), and Agricultural Research Service (ARS). While NTT has been around for several years (e.g., a version of NTT is used in the Chesapeake Bay, and another version is used in Arkansas), this version represents the first national version of the tool. NTT was developed by using the Agricultural Policy Environmental eXtender (APEX; Williams et al., 2000). Inclusion of APEX allows users to evaluate other farm level conservation practices such as filter strips, terraces, buffer strips, etc., that could not be evaluated using the Nitrogen Trading Tool. As a result of this effort, users also have access to various other relevant indicators (e.g., water quantity, sediment losses and crop yield changes) to help them make informed decisions about conservation practice implementation.

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Is this tool national in scope?

Yes, this tool can be used anywhere in the continental United States. NTT has been validated using the regional information for majority of the U.S. States (Please refer to “validation” tap in NTT program). However, in most cases model parameters are generalized. TIAER is currently working with local collaborators to create region-specific parameters for areas of the country where measured data exist that can help refine estimates generated by NTT. The NTT tool currently includes region-specific parameters for the Great Lakes region as well as State of Ohio and Delta region off the Upper Mississippi. Revised parameters will be available in future releases of the tool as they become available.

Will my data be protected?

Yes, each entity using NTT is provided with a password, which is protected so no one else sees your data but you.

What crops are included?

Pastureland, as well as most major cultivated crops for each State, are included in the tool.

What conservation practices are included?

The tool simulates a variety of management and conservation practices including irrigation, tile drains, nutrient management (type, timing, placement, and rate), no till, conservation till, cover crops, ponds/water and sediment control basins, wetlands, buffers (forest and grass), grass waterways, contour buffer strips, terracing, manure treatment, and rotational grazing. Users can also simulate land conversion to perennial crops or forest.

What is the plan to improve/maintain NTT over time?

NTT is housed and maintained at Tarleton State University. USDA’s Office of Environmental Markets is committed to contributing to the update and maintenance of NTT as long as it is useful to stakeholders. NTT versions will be updated regularly with regional parameters provided by ARS, as well as with improved functionality and features as needed.

What is the engine behind NTT?

NTT uses the APEX model to simulate edge-of-field losses, as well as to simulate routing between fields. The Agricultural Policy Environmental eXtender (APEX; Williams et al., 2000). Inclusion of APEX allows users to evaluate other farm level conservation practices such as filter strips, terraces, buffer strips, etc., that could not be evaluated using the Nitrogen Trading Tool.

What type of environmental data and sources are used to simulate NTT?

NTT collects soil, slope, and weather information from national databases, based on the location of your field. Soil data come from the National Soil Survey database (SSRUGO). NTT simulates your field using only the three predominant soils in your field (by percent coverage). Weather is pulled from the national PRISM database. NTT simulates the crop management rotation using 35-years of recent historic weather. Finally, slope information is calculated based on the 30m resolution digital elevation model (DEM) map layer.

What do the nutrient and sediment losses estimated by NTT represent?

Because your rotation is simulated over 35 years of historic weather, the nitrogen (N), phosphorous (P), and sediment losses represent the average annual losses at the edge of the field for a given management scenario. Users can also view the results graphically by year in order to view inter-annual variability, or by month, to view average monthly variability.

Why did USDA support the development of NTT?

USDA’s interest in developing NTT was for water quality markets, which require methods and tools for quantitatively estimating nutrient and sediment losses from a variety of agricultural and best management practices. However, the tool can be used for a variety of applications, including farmer education and outreach, corporate sustainability, and academic or analytical applications.

Projects

How can I download a project file off NTT?

To download a NTT project, you need to navigate to the project dashboard (this is the initial page where you can see the list of projects you have created). Next to the name of each project, there is a group of icons under the column named "Actions". Clicking on the

icon will allow you to download your project.

Fields

Soils

Are the estimated water quality outcomes (i.e., N, P, sediment loading) in the model are a function of soil properties?

Yes. APEX in NTT is a physical-based model. That means water quality and soil properties are directly related.

When I submit my map, I get an error that no soils were selected. Why?

The are two possible reasons for this:: 1) The USDA-NRCS soil survey map is not completed for that specific location; or 2) the soil data are incomplete. For example, the soil data returned from SSURGO might be missing the soil bulk density. We are continuously evaluating and resolving soils issues when they arise. If you encounter any issue, please contact us and let us fix the problem.

Does the NTT model reflect/estimate changes in soil properties that may occur due to adoption of soil health practices (e.g., no-till/reduced till, cover crops, nutrient management, & conservation crop rotation, etc.)? If so, which soil properties?

The answer is “yes”. We define soil properties as both the physical (e.g., soil texture or bulk density, etc.) and chemical (e.g., pH or cation exchange capacity, etc.) characteristics.

The following list of soil properties are among the majority of soil properties that change with adoption of soils health practices calculated by NTT program. However, most of these parameters are not presented in the result page at this time. We are working on a report to display some of these properties. In the meantime, please contact us if you are interested in these variables and we can help summarize them from your NTT project.

       Soil pH

       Soil Electrical Conductivity (EC)

       Cation Exchange Capacity (CEC)

       Soil Nitrogen ()

       Soil Phosphorous (organic and soluble)

       Soil Organic Carbon (SOC)

       Soil Texture

       Available Water Holding Capacity

       Bulk Density (BD)

       Saturated Hydraulic Conductivity

       Crop Yield

How is the slope for each soil determined?

NTT uses the 30m resolution Digital Elevation Model (DEM) data to calculate slope for each soil selected for your field. Note that the estimated slope used by NTT will likely vary from the slope as estimated by the SSURGO soils database.

Operations

Can I plant multiple crops at the same time?

Yes. APEX, the model that underlies NTT, can simulate up to 10 crops at once. The most common application for this is early planted cover crops that are seeded into the main crop before harvest. To simulate a scenario like this, simply choose a plant date for your cover crop that is prior to the harvest of your main crop. You will want to select a seeding method such as aerial seeding of no-till drill that will result in minimal disturbance of the main crop.

How do I simulate a multi-species cover crop?

We are working on implementing a short cut for multi-species cover crops. In the meantime, to add a multi-species cover crop you will want to add a crop to your rotation (instead of using the cover crop function), select the first plant in the cover crop mix, planting date and end of season date (which is usually prior to planting date of the spring crop). Next, add a new crop to your rotation with a planting date one day after the first species in the cover crop mix (this minimizes confusion in the model), a kill date (the next day after). Another consideration is the seeding rate (an input in the planting operation). You will want to adjust the seeding rate of each species in the mix to represent its relative proportion in the mix. Please see the tips for adding a commercial cover crop/winter crop for how to properly place the end of season date within your rotation if the cover crop is planted in the last year of the rotation.

What is End of Crop Season?

The End of Crop Season operation tells the model that the crop is terminated. Without this operation, the model will assume that the crop will re-grow in the next crop season. Perennial crops such as hay, grapes, almonds, etc., will not have an end of season operation as they will re-grow after harvests. For annual crops, however, there should always be an end of crop season operation placed the day after the final harvest to indicate to the model that the crop is terminated.

How do I add a commercial cover crop/winter crop?

A commercial cover crop should be added as a normal crop, not using the “add cover crop” feature. By adding the crop manually you will be able to specify fertilizer applications, tillage, and harvest operations, whereas the cover crop feature has a limited crop selection, and assumes that crop is not fertilized, tilled, or harvested.

Please note that when manually entering a winter crop you should be careful about the “end of season date”. If planting a commercial cover crop in last year of the rotation (e.g., year 3 of a 3-year rotation), then any operations that happen after December 31, including harvest and end of season, should be placed in year 1. Similarly, if you have only a single year rotation your plant and harvest date should both be in year 1. This is because the model runs the simulation on a continuous loop.

Below is an example of a one-year rotation with a cover crop/winter crop:

Year 1, May 1, Plant -- Corn
Year 1, October 15, Harvest -- Corn
Year 1, October 16, End of Season – corn (indicates to model that corn crop is terminated)
Year 1, October 17, Plant -- cover crop
Year 1 April 15, end of season -- cover crop (indicates that cover crop is terminated)

Why do operations dates only specify “year 1”, “year 2”, etc. and not an actual year?

APEX uses year one as the start of the simulation but translate it into real years according to the parameters set up in the Apexcont.dat file. In NTT, year 1 corresponds to 1985 and it will run for 35 years (until 2019 at this moment).

What happens if I do not enter the plant population in my planting operation for the crop?

NTT provides a default plant population from its existing databases if this field is left blank.

The composition for commercial fertilizer is defined as Element-N and Element-P. Does this mean pure N and pure P?

Yes. When applying commercial fertilizer the user has the option of selecting “element-N” and/or “element-P”. These options allow the user to specify the total N and total P applied without specifying the form. However, users also have the option of specifying the type of commercial fertilizer applied. For these fertilizers, NTT shows the default fraction of N (which represents soluble N), and the fraction of P2O5 (not total P). NTT will convert P2O5 to total soluble P on the back end by multiplying it by 0.45. It is highly recommended that user select the commercial fertilizer from the provided list. This is because the specific ammonia fraction is associated with each specific fertilizer.

What is the nutrient content of manure fertilizer?

Manure fertilizer includes four major nutrients: organic N and P, soluble P and N. Also, the fraction of organic matter in manure is considered in NTT simulations. For each manure type, NTT has set defaults for the nutrient content of manure. Users have the option of editing the manure nutrient composition to more closely reflect the content of manure applied to their field.

In grazing operation, why does NTT ask for total animal units instead of total animals and what does that mean?

Animal Units are a standard unit of measurement where 1AU is equal to 1000 lbs. of animal live weight. For example, one beef cow corresponds to 1AU (1000 lbs.), one dairy cow is considered equal to 1.4AUs (1,400 lbs. each), and 1 sheep is considered equal to .2AUs (200 lbs. each). For example, sheep conversion unit is 0.2. That means 5 heads of sheep is equal to one head of beef.

Management Scenarios

Why did my nitrogen/phosphorus/sediment loads go up after I applied conservation practices?

If your nutrient losses do not seem to match your expectations, you should take a look at the following:

1) Check your management files. Make sure that your dates are correct. Often when editing dates, users make mistakes with the dates of operations. For example, a tillage operation after planting. The order of operations will affect the model simulation. Please ensure that your dates correct.

2) If your management files are correct, you may be seeing one of the following phenomena
a. I reduced nitrogen, but my nitrogen loads went up. Nitrogen reductions that cause a significant drop in yield may result in increased nitrogen losses from the field because crop uptake is reduced and more nitrogen is available to be lost to the environment.
b. I put in a cover crop but my nitrogen loads went up or stayed almost the same. When you have tile drains on your field, cover crops may have the effect of reducing surface nitrogen losses but increasing nitrogen losses to tile drains. Or it’s possible that if you put in a commercial winter crop or manually added a cover crop you inadvertently simulated a year of fallow which usually causes increases in nutrient and sediment loads. This happens if the winter crop comes at the end of the rotation and you did not specify the harvest/end of season operation to occur in year 1. Please see “how do I add a commercial cover crop” for tips on manually adding a cover crop.

What does the Start and Stop Month and Year in Autoirrigation/Autofertigation Conservation Practice mean?

This allows you to specify the months when the irrigation or fertigation is applied in the field. Otherwise, the irrigation/fertigation event will not be triggered.

On the Conservation Practices page, under the Grass Buffer/Forest Buffer section, the following question is displayed: “Is the buffer area included in your AOI (area of interest)?” What does this mean?

This answer is asking of the area which is being designated as a buffer was included in the field boundary that you drew or whether the buffer assumed to be adjacent to the field boundary. If the answer is “YES”, NTT will subtract the area of the buffer from the field and consequently reduces the total annual yield for whole field. If your answer is “NO”, NTT will simulate a buffer that is adjacent to the field and would not affect the total yield.

What is meant by "Fraction of field controlled by pond/WASCB”?

This question is asked when you select the pond/WASCB option from the list of structural conservation practices. The question is asking for the fraction of the drainage area within the field that flows into the pond. This allows the program to determine how much water, sediment, and nutrients are trapped in the pond.

Why are the number of crops available limited and different in some states?

There are 120+ crops available in NTT databases. However, we included crops available for each state using two criteria: A) crops that are most cultivated in each individual state, and B) the crop has been validated based on local crop information.

I plant my cover crop after terminating my corn and/or soybean in fall and terminate my cover crop in March of next year. However, I do not see any effect of my cover crop on sediment and nutrient losses. Why?

When the cover crop is harvested early in late winter/early spring, it likely did not have enough time to grow to be effective. Try postponing your cover crop termination date to resolve the issue.

Results

What impact does the soil P test have on my results?

When you enter the soil P test, we use the P value as the starting value for the phosphorus in your soil. If you do not have a P test you may leave it blank and we will use default values. Because phosphorus is a stock in the soil and the simulation for the model is over a period of 35 years, the phosphorus stocks are influenced more by fertilizer and manure management on the field. The simulation of Soil P has been addresses in the recent version of NTT. Soil P value is “refreshed” at the beginning of the rotation throughout the simulation. This new routine provide better evaluation of the Soil P on water quality and crop yield in particular for those who may have reduced phosphorus applications on their field due to high soil P.

How do I interpret my tabular water quality report?

The tabular report shows the average annual nutrient losses and yields over the period of simulation. Your scenarios are simulated in the APEX model over a period of 30 years using historic weather and soils data from the SSURGO database. The tabular report shows the average losses/yields. You may customize this report by specifying the years of simulation that you wish to include, or by selecting “wet years” or “dry years” options which will show the average of the top quartile of wet or dry weather years, respectively. Users may also select which scenarios they would like to view and/or compare.

Is it possible to download my project results?

Yes. Please use the PDF download function in the results page to download a PDF copy of your project results.

What does Confidence Interval represent for the results?

The confidence interval (CI) represents the variation of weather and yearly changes in soil properties within the 35-year of simulation period. However, the CI value is most affected by variation in weather.

What to dry and wet years tabular reports represent?

To calculate the dry and wet year’s reports, NTT takes the annual averages of the 25% driest years over the period of the simulation (35 years). The same calculation is applied for wet years by taking the 25% wettest years and averaging them. These reports are meant to show trends in nutrient and sediment losses over wet and dry conditions for your region.

Weather

How often is the weather file updated?

The weather used for simulations in NTT is updated (expanded every year) with the information obtained from the (updated) PRISM site. The last update was completed in Dec. 2019.

Frequently Asked Questions