Management Zones Classiﬁed With Respect
to Drought and Waterlogging
Department of Soil Sciences, Division of Precision Agriculture, Swedish University of Agricultural Sciences,
SE-532 23 Skara, P.O. Box 234, Sweden
Department of Soil Sciences, Division of Hydrotechnics, Swedish University of Agricultural Sciences,
SE-750 07 Uppsala, P.O. Box 7014, Sweden
Abstract. Within-ﬁeld variations in potential grain yield may be due to variations in plant available soil
water. Diﬀerent water holding capacities aﬀect yield diﬀerently in diﬀerent years depending on weather. By
estimating plant-water availability in diﬀerent weathers, scenarios could be created of how yield potential
and thereby fertilizer demand may vary within ﬁelds. To test this, measured cereal grain yields from a dry,
a wet and an intermediate year were compared with diﬀerent soil moisture related variables in a Swedish
arable ﬁeld consisting of clayey and sandy areas. Soil water budget calculations based on weather data and
maximum plant available water (PAW), estimated from soil type and rooting data, were used to assess
drought. A reasonable correlation between estimated and measured soil moisture was achieved. In the dry
year, drought days explained diﬀerences in yield between the clayey and the sandy soil, but yield was better
explained directly by maximum PAW, elevation, clay content and soil electrical conductivity (SEC). Yield
correlated signiﬁcantly with SEC and elevation within the sandy soil in the dry year and within the clayey
soil in the wet year, probably due to water and nitrogen limitation respectively. Dense SEC, elevation and
yield data were therefore used to divide the ﬁeld into management zones representing diﬀerent risk levels
for drought and waterlogging. These could be used as a decision support tool for site-speciﬁc N fertil-
ization, since both drought and waterlogging aﬀect N fertilization demand.
Keywords: grain yield, management zones, plant available water, site speciﬁc fertilization, soil electrical
Site-speciﬁc fertilization should be optimized with regard to potential crop yield.
Estimating within-ﬁeld variation in potential yield is therefore of major concern in
precision agriculture. Yield maps have sometimes been used to demarcate a ﬁeld into
management units for fertilization, but crop response to diﬀerences in soil properties
across a ﬁeld may diﬀer between years due to variation in weather between years (Delin
et al., 2005). Therefore, there is often a lack of consistency in the spatial patterns in
yield from one year to another. Homogeneous management zones can probably be
identiﬁed from seasonally stable factors but in-season management of these zones has
to consider seasonally variable factors such as rainfall (Machado et al., 2002).
Precision Agriculture, 6, 321–340, 2005
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