Agriculture Reference
In-Depth Information
Figure 4.2
. Distribution of (A) percentage of arable land and (B) soil water holding capac-
ity by county in the NCR. Water holding capacity is the amount of water that can be held in
a soil between its field capacity (drained upper limit) and the wilting point of the vegetation,
expressed as the volumetric water content (% of total soil volume). This is a function of soil
texture and is expressed for the upper 250 cm of the soil profile. Data from NRCS (1991).
Statewide 30-year patterns of rain-fed crop yields for corn and soybean range
from 3-7 Mg ha
−1
(48-112 bu acre
−1
) for corn and 1.4-2.6 Mg ha
−1
(21-39 bu acre
−1
)
for soybean across the NCR (Fig. 4.3). Corn and soybean yields for this time period
(1971-2001) were highest in Iowa and lowest in North Dakota. The upward trends
in corn and soybean yields for the NCR since 1971 (Fig. 4.4) reflect improvements
