MOST RECENT SAMPLING DATE: 5/19/2017
100% FALL-APPLIED N
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The Data Summary provides an overview of site information, testing dates and corresponding soil test results as well as when any N applications were made to the site. The pounds of nitrate and ammonium-N are calculated and added to represent pounds of Plant-Available N in the upper 2 feet of the soil profile. The percent ammonium-N is also calculated so that changes in stablized-N (ammonium-N) can be observed over time.
REVIEWER COMMENTS
Reviewer comments offer an interpretation of what the soil test information represents after each testing date. The comments are provided by Dr. Howard Brown. Dr. Brown created the original concept of N-WATCH over four years ago. To-date, Dr. Brown has offered reviewer comments to well over 200 sites over the past four years. His comments reflect what science has taught us as well as what experience with reviewing sites over the years provides.
DATA GRAPHS
1st GRAPH. Shows the following:
- Pounds of Plant-Available N/Acre (upper 2 ft. of soil profile). Red represent nitrate-N and blue represents ammonium-N. Together, they represent Plant-Available N. The scale for total Plant-Available N in pounds N/acre is on the left side of the graph.
- Green horizontal line and green shaded area represents the time and amount of N applied. The green line represents the accumulative amount of N applied over time.
- Thin, vertical blue bars represent weekly rainfall totals (total for 7 days). The scale for weekly rainfall is on the right side of the graph.
- Pounds of Plant-Available N/Acre (upper 2 ft. of soil profile). Red represent nitrate-N and blue represents ammonium-N. Together, they represent Plant-Available N. The scale for total Plant-Available N in pounds N/acre is on the left side of the graph.
- Green horizontal line and green shaded area represents the time and amount of N applied. The green line represents the accumulative amount of N applied over time.
- Thin, vertical blue bars represent weekly rainfall totals (total for 7 days). The scale for weekly rainfall is on the right side of the graph.
2nd GRAPH. Shows the daily maximum temperature of the soil at a 4" depth without any cover (bare soil). The bare soil temperature at 4 inches is used to determine the activity of soil microorganisms. Once the soil temperature reaches 50 degrees F in the Fall (November) it is assumed that the soil temperature will continue to trend downward, slowing or essentially stopping microbial activity. Slowing or stopping microbial activity helps keep the applied anhydrous ammonia in a stable ammonium-N form (stops conversion of ammonium-N to nitrate-N, a process referred to as Nitrification).
3rd GRAPH. This graph reflects both nitrate and ammonium-N as ppm over time. It was the first graphic offered through the original N-WATCH Program (now called N-TRACKER/Soil). When the corn reaches a height of 6 to 12 inches (red box), the soil nitrate-N should reach 25 ppm (black dotted line). Nitrate-N concentrations below will be used to estimate how much supplemental N is needed to optimize harvest yield according to research published by Iowa State University (Late-Spring Nitrate Test or LSNT). For more information visit Nitrogen Fertilizer Recommendations for Iowa.
