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Theory


The data and calculations used on this website are taken from the report Decision Aid for Estimating Seed-Placed Fertilizer Rates published on December 31, 2008 by R.H. Gelderman from the Plant Science Department, South Dakota State University. The document is available for download below.

Decision Aid for Estimating Seed-Placed Fertilizer Rates - Final Report can be downloaded here.

This tool uses regression coefficients (crop stand upon fertilizer rate) that were developed using published studies from North America. Coefficients are adjusted for soil texture and soil moisture based on data collected under standardised conditions. The tool uses the equation:



F = 30S (-T)/CRMX



F = fertilizer material (lb/ac or kg/ha).
S = seed furrow opening (in or cm).
T = tolerated stand loss, as a percent, due to fertilizer applied with seed over typical stands, where no fertilizer is applied.
C = negative regression coefficient for the selected crop X fertilizer (%/lb/ac or %/kg/ha).
R = row spacing (in or cm).
MX = planting soil moisture and soil texture coefficients.

Negative Regression Coefficients

Alfalfa/Lucerne Barley Canola Corn Cotton Flax/Linseed Lentil Mustard Oat Pea Safflower Sorghum Soybean Sunflower Wheat Wheat-durum
Urea (46-0-0) -6.373 -1.207 -4.457 -0.965 -3.201 -7.208 -2.706 -2.903 -1.634 -1.489 -3.175 -2.521 -3.33 -2.258 -1.436 -1.468
UAN (28-0-0) -2.821 -0.281 -1.873 -0.236 -0.64 -2.495 -1.29 -2.017 -0.551 -0.799 -1.539 -0.825 -1.703 -0.556 -0.258 -0.396
Am.Nit (34-0-0) -2.924 -0.432 -3.034 -0.215 -0.621 -2.479 -1.825 -2.604 -0.807 -1.062 -2.271 -1.038 -2.378 -0.993 -0.893 -1.107
DAP (18-20-0) -1.074 -0.477 -1.567 -0.236 -0.645 -1.153 -1.141 -1.182 -0.545 -0.703 -1.082 -0.862 -1.08 -0.306 -0.541 -0.617
MAP (11-22-0) -1.107 -0.302 -0.971 -0.161 -0.607 -0.902 -1.115 -1.235 -0.578 -0.678 -0.777 -0.465 -1.097 -0.367 -0.406 -0.7
TSP (0-20-0) -0.955 -0.179 -0.977 -0.099 -0.207 -0.655 -0.587 -1.061 -0.21 -0.247 -0.61 -0.274 -0.592 -0.335 -0.266 -0.328
APP (10-15-0) -0.65 -0.199 -0.685 -0.037 -0.455 -0.537 -0.582 -0.34 -0.213 -0.143 -0.583 -0.172 -0.478 -0.244 -0.105 -0.234
7-9-6 -0.381 -0.058 -0.483 -0.053 -0.255 -0.291 -0.474 -0.303 -0.193 -0.218 -0.387 -0.166 -0.597 -0.163 -0.143 -0.153
9-8-7.5 -1.157 -0.125 -0.673 -0.154 -0.468 -0.827 -0.502 -0.694 -0.378 -0.222 -0.557 -0.501 -0.688 -0.328 -0.14 -0.193
3-8-15 -0.573 -0.098 -0.613 -0.103 -0.313 -0.617 -0.424 -0.493 -0.099 -0.24 -0.452 -0.263 -0.521 -0.155 -0.07 -0.165
4-4.4-8 -0.303 -0.081 -0.269 -0.045 -0.123 -0.162 -0.314 -0.252 -0.121 -0.121 -0.286 -0.122 -0.506 -0.098 -0.05 -0.2
KCL (0-0-50) -1.505 -0.618 -1.479 -0.473 -0.982 -1.419 -1.632 -2.357 -1.067 -1.282 -1.426 -1.189 -2.166 -0.764 -0.891 -1.156
KsMg (0-0-18-22S-11Mg) -0.725 -0.364 -0.981 -0.215 -0.623 -0.749 -0.799 -0.883 -0.782 -0.344 -0.663 -0.803 -0.822 -0.261 -0.558 -0.578
KSul (0-0-42-17S) -0.97 -0.212 -1.177 -0.095 -0.564 -0.954 -0.824 -1.398 -0.507 -0.449 -0.693 -0.984 -0.693 -0.337 -0.474 -0.569
ATS (12-0-0-26S) -4.418 -1.306 -2.92 -0.3 -2.09 -1.981 -2.856 -4.54 -1.889 -4.557 -2.976 -1.774 -4.001 -1.758 -1.169 -0.934

Soil Coefficients

Moist Borderline Dry
Fine 0.75 1.0 1.5
Medium 1.0 1.5 2.0
Coarse 1.5 2.0 2.5

Acknowledgements