Precision Agriculture, 3, 237–257, 2002
© 2002 Kluwer Academic Publishers. Manufactured in The Netherlands.
Measurements of Mouldboard Plow Draft: II.
Draft-Soil-Crop and Yield-Draft Associations
D. R. LAPEN, H. N. HAYHOE, G. C. TOPP, N. B. McLAUGHLIN,
AND E. G. GREGORICH
Eastern Cereal and Oilseed Research Centre, Agriculture and Agri-Food Canada,
Ottawa, Ontario, K1A 0C6
W. E. CURNOE
University of Guelph-Kemptville College, Kemptville, Ontario, K0G 1J0
Abstract. The primary objective of this investigation was to evaluate some potential causal associations
between draft derived from a 3-bottom mouldboard plow during normal fall ﬁeld operations and soil-crop
properties at a ﬁeld site near Winchester, Ontario, Canada. A secondary objective was to investigate, in a
preliminary manner, associations between draft and crop yield (corn, soybean, and wheat). Regression tree
analysis indicated that draft variability was best explained by ﬁeld location, crop type, soil cone penetration
resistance in the plow layer, and soil texture in the plow layer. Draft was found to generally increase with
cone penetration resistance in the plow layer and soil clay content. Corn yields were negatively associated
with draft. The reverse was true for the soybean yields, and a combination of negative and positive draft vs.
yield relationships existed for the wheat plots. The overall results indicated that draft data collected during
normal ﬁeld operations can be useful for producers interested in identifying areas in the ﬁeld where soil
strength/compaction might be problematic with regard to crop yields.
Keywords: mouldboard plow draft, cone penetration resistance, spatial variability, regression trees
Soil strength/compaction has been recognized as an important factor in crop growth and
yield (Soane and van Ouwerkerk, 1994). Recent investigations on soil strength/compaction
and crop relationships for ﬁner textured soils in eastern Ontario, Canada (Gregorich et al.,
1993; Lapen et al., 2001b) have identiﬁed a requirement for spatially continuous estimates
of bulk soil strength related properties to help inform farm management decisions. If plow
implement draft could be reliably related to soil strength/compaction at the ﬁeld scale,
then strength/compaction patterns could be identiﬁed via spatially continuous maps of
draft. Such information would be useful to producers interested in minimizing the effects
of strength/compaction on crop yield. Plow implement draft is an appropriate factor in
that measurements are continuous (minimizes uncertainties associated with predicting the
variable at unsampled locations), soil strength properties reﬂected by the plow can poten-
tially represent a substantial soil volume in the dominant root zone of most agricultural
plants (Dwyer et al., 1988), and draft measurements can be collected during normal ﬁeld
operations (McLaughlin et al., 1993; Perfect et al., 1997).
Cone penetrometers can provide in situ measures of soil strength (American Society
of Agriculture Engineers, 1999); but as point measures, large numbers of observations