Illinois Fertilizer
Conference Proceedings
January 27-29, 2003
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T.R. Peck1
The objective of this study is to evaluate soybean and corn crop yields in
relation to soil test levels for P and K in an east central Illinois 40-acre
(16.2 hectare) field residual from P and K fertilizer application since the
last application in the fall of 1986. Composite soil samples for mapping soil
test levels are collected from the center of 5-rod grid areas (16 by 16 field
grid pattern, 82.5 feet grid area, 25 meter) and crop yields are measured with
a combine yield monitor.
The 40-acre field, located in Piatt County near Mansfield, is under University
Trust Management with recorded cultural management (crops grown, yields and
fertilizer analysis and rate) since 1961. Soil types are dominantly Drummer
sicl, Flanagan sil, and Harpster sicl. The field was cropped to soybean in 2002
and will be corn in 2003. Soil samples were collected in April of 2002.
The field average soybean yield for 2002 was 50.86 bu/a, which compares with
2000 at 55.5 bu/a, 1998 at 44.8 bu/a, 1996 at 47.3 bu/a, 1994 at 60.7 bu/a,
1992 at 42.3 bu/a, and 1990 at 65.5 bu/a. An adjoining 80-acre field that has
been regularly fertilized with phosphorus and potassium yielded 60.84 bu/a.
Soil tests on soil samples are in the process of analysis, along with the mapping
of field soybean crop yield.
1T.R. Peck is a professor
of soil chemistry extension, Department of Natural Resources and Environmental
Sciences, University of Illinois.
