- New, updated versions of the NRCS-ARS N Index are available this winter for download to desktop computers or as smartphone apps.
- The free program gives quick guidance for N-management decisions.
- Through a simple set of screens, it incorporates information on soil layers, manure, fertilizers, irrigation, crops, hydrology and other factors that can affect N loss.
- NRCS is incorporating the index as another tool for growers’ conservation efforts.
This sample recommendation screen helps users adjust their fertilizer and/or manure application rate to supply a crop's N requirements. This user reduced the manure rate from 15 to 10 tons, and still has 362 pounds N per acre, for an expected crop N uptake of 180 pounds per acre. (The previous crop was alfalfa.) Users can quickly assess different N inputs and/or select what percentage to assign for each N source.
A new 4.5 version of the Nitrogen Index, available this winter from NRCS-ARS, makes the program quicker and easier to use as a tool for nutrient-application decision tool.
“This tool puts details together so you can see the interaction of slope, rainfall, and the application of different nutrients,” says David Klee, a Kentucky service provider working with dairy and beef producers using the index.
The index has value especially for row-crop farmers who apply significant amounts of manure, he believes.
“The index highlights places with higher potential to leach nitrogen,” explains Marty Adkins, state resource conservationist with USDA’s Natural Resources Conservation Service in Des Moines.
“The index can be a new tool to evaluate nitrogen and phosphorus management.” It can lead to using nutrients more efficiently, says Adkins. “The aim is for the nutrients you apply to translate into yield rather than running off or leaching out of the root zone.”
It is also relatively easy to work with, according to Klee. “I do a lot of consulting at kitchen table meetings, where you can take aspects of the index and understand that you can’t treat all fields alike.”
Similar to various state P indices, the N Index uses a series of input screens that cover soil layers, manure, fertilizers, irrigation, crops, off-site factors, water management and hydrology, and qualitative factors to rank the risk of N leaching, atmospheric and surface loss.
It has been calibrated for a wide variety of cropping systems in the U.S., China, Mexico, Argentina, parts of Spain, and the Caribbean. The new 4.5 version can also assess direct and indirect emissions of nitrous oxide gas (N2O), an additional N-loss avenue.
And, you can assess a given farm or field without inputting large amounts of data, according to Jorge Delgado, ARS research soil scientist.
The new index version has performed well in tests, Delgado adds, comparing how different management practices affect N losses and distinguishing medium, low, and very low-risk practices from high- and very-high-risk alternatives.
An N index smartphone application was published in 2013, and an improved (4.5) app for Android debuts this winter.
Download the most current N Index (4.4.2) for free. You must have the most recent version of Java to run the index.