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SNAP - Soil Nutrient Assessment Program

SNAP (Soil Nutrient Assessment Program), a component of the USDA/ARS Soil and Water Hub, is a web-based tool that provides an estimate of plant-available nutrients that the soil naturally provides.

Soil test fertilizer recommendations have long been predicated upon response curves generated from fertility trials across the country. These response curves have been compared to relative yield which provide probability ranges for a response to varying fertilizer inputs. Category responses include very low, low, adequate, high or very high inversely related to probability of a response to various inputs of nitrogen, phosphate, and potassium (N, P, and K).

New soil test methods, increases in computing power and access to the internet have enabled development of an interactive tool that is based on plant available NPK from both the inorganic fraction and organic pool of the soil. The new methods provide an estimate of plant available nutrients that the soil naturally provides, which has largely been ignored for decades.

Since we have access to large datasets we can calculate the amounts of NPK required growing crops in lbs NPK per bu of the desired crop. For example, it requires 100 lbs of N, 50 lbs P2O5, 50 lbs K2O to grow 100 bu corn. These are the base numbers from which we subtract the soil test data after converting from the analytical ppm to Lbs P2O5 or lbs K2O. This is a straight subtraction. It also eliminates the need for "calibration data" since the soil tests reflect the soils inherent fertility. Using the example above, of 100, 50, 50 of N, P, and K required and soil test results of 25, 35, 45 then the fertilizer needed would be 75 N, 15 P2O5 and 5 K2O. This is a simple approach that doesn't get lost in relative yield-crop response curves that have been used for decades from differing geographical areas.

This tool will include current fertilizer prices, soil test inputs, and crop based county averages for the last 15 years that will predict the chances of making the yield goal the user inputs compared to historical yield data for their county and calculate the fertilizer cost with and without soil testing compared to user input yield goal and county average. This tool will allow the user via the internet to produce a more straightforward approach to realistically planning next year's fertilizer inputs and associated cost. It will also show the benefits of soil testing for increased fertilizer efficiency and reduced environmental impact.

Dataset Info

These fields are compatible with DCAT, an RDF vocabulary designed to facilitate interoperability between data catalogs published on the Web.
FieldValue
Authors
USDA ARS Grassland Soil and Water Research Laboratory
Product Type
Software Tool
Spatial / Geographical Coverage Area
POLYGON ((-95.393066704273 49.390718622262, -122.99072295427 49.046272144223, -124.39697295427 47.880743391454, -124.74853545427 42.562524148417, -122.81494170427 37.589572543393, -119.12353545427 33.29533705186, -116.31103545427 32.260816853318, -114.55322295427 32.705654921671, -110.68603545427 31.214370510697, -108.40087920427 31.214370510697, -107.52197295427 31.813788042556, -106.64306670427 31.813788042556, -103.12744170427 29.086579846985, -102.07275420427 29.699190146047, -100.13916045427 28.624713962673, -97.678222954273 25.494524269057, -96.623535454273 28.160807105531, -94.689941704273 29.086579846985, -91.701660454273 29.546383858427, -90.119629204273 28.93285262998, -89.240722954273 30.004105722576, -86.604004204273 30.156213563649, -84.143066704273 29.851764343352, -82.385254204273 28.470304068247, -81.154785454273 25.653084153224, -80.275879204273 25.653084153224, -79.748535454273 26.757059094238, -81.330566704273 30.45972578952, -80.803222954273 31.664294451237, -75.529785454273 35.184287601126, -74.123535454273 39.784622524538, -72.717285454273 40.989576410551, -70.256347954273 41.780872961995, -70.256347954273 43.716860745734, -67.268066704273 44.599596818623, -67.443847954273 47.048918724375, -69.025879204273 47.525858859652, -70.080566704273 46.203916132075, -71.311035454273 45.59226206518, -74.475097954273 45.098086535875, -76.232910454273 44.22289853526, -78.869629204273 43.843774374786, -79.221191704273 42.691859658448, -82.736816704273 41.518177644287, -82.209472954273 43.334503843965, -83.615722954273 46.082124300382, -84.670410454273 46.92901151486, -89.768066704273 47.880743391454))
Spatial / Geographical Coverage Location
Contiguous United States
Publisher
USDA Agricultural Research Service
Contact Name
White, Mike
Contact Email
Public Access Level
Public
Related Content
License
Funding Source(s)
Agricultural Research Service
Program Code
005:037 - Department of Agriculture - Research and Education
Bureau Code
005:18 - Agricultural Research Service
Modified Date
2019-01-25
Release Date
2018-04-18
Ag Data Commons Keywords: 
  • Agroecosystems & Environment
  • Soil
  • Nutrients
  • Agroecosystems & Environment
  • Water
  • Hydrology
  • Agroecosystems & Environment
  • Weather and Climate
  • Agroecosystems & Environment
  • Management
  • Plants & Crops
  • Crop production
  • Nutrient Management
  • Agroecosystems & Environment
  • Water
  • Water quality
  • Plants & Crops
  • Crop production
  • Agroecosystems & Environment
  • Soil
  • Agroecosystems & Environment
  • Water
  • Agroecosystems & Environment
  • Plants & Crops
State or Territory: