Web-based Adapt-N case study on N use
click image to zoomFigure 1: Variability of soils was mapped using aerial photographs and soil survey data. Precise estimation of corn nitrogen (N) needs has been difficult due to many interacting and complex processes that affect N in soils and crops. Over the past years, we developed the Web-based Adapt-N tool to provide improved in-season N recommendations based on model simulations of soil N dynamics and corn N uptake. The tool is currently available for farms in the Northeast and Iowa, and will be expanded for use in the entire eastern USA for the 2012 growing season. Adapt-N is built around the powerful Precision Nitrogen Management (PNM) model, which uses information of soil and crop management, organic inputs and newly-developed high-resolution weather information (3x3 mile grid) to develop accurate nitrogen recommendations. The Adapt-N tool is especially useful for in-season N rate applications, when the crop N needs are more predictable.
For the 2011 growing season, we developed a case study to evaluate the utility of the Adapt-N tool for a large grain farm in western New York. The area of interest consisted of 87 corn fields that comprised nearly 1200 acres. Fields were digitized in ArcGIS 9.3 using 2005 aerial photographs (Figure 1). The digitized fields were then used as an overlay to clip a soil survey, and linked to the appropriate attributes that were used as inputs for the Adapt-N tool. Of the corn acreage, 76% was mapped as silt loam, 23% as silty clay loam, and 1% as gravelly soil. Soil organic matter varied widely, from 0.9% to 9.9%. The study area consisted of two sets of fields that were located several miles apart. Therefore, two different location coordinates were set up in the Adapt-N tool to access the high resolution climate data.
Nitrogen was applied to the field through pre-plant broadcast urea plus UAN solution banded at planting. Three rates of urea were used, 112, 126, and 140 lbs/acre, depending on soil type. UAN solution was applied at one of three rates, 54, 58, and 78 lbs/acre.
Western NY experienced unusual weather for the 2011 growing season. The months of April and May proved to be the wettest on record (over 6 inches in each month), but they were followed by a dry period in June (2.5 inches) and July (less than 1 inch). There were two distinct windows for planting: Fifty-eight percent of the corn ground was planted early - before May 1 -, and 42% was planted late in the season - after June 1.
Adapt-N input information varied based on soil and management practices. All fields were planted at 32,500 plants per acre and were grown as first year corn after soybeans without manure applications. Conservation tillage was used with an estimated 75% residue left on the surface. Field specific information was also entered for soil organic matter (from recent soil tests), soil type, planting date, corn variety, fertilization regime, and yield goals.