Agriculture Reference
In-Depth Information
Figure 4.5
. Distribution of mean grain yields (Mg ha
-1
) for non-irrigated (A) corn and
(B) soybean by county in the NCR (1971-2001). See Fig. 4.3 legend for data source.
The Crop Stress Index (CSI) is a simpler index to use and requires less data than
the PDI. The CSI is estimated by the equation
(
)
CSI =
DP
10
/
+
1
where
D
10
is degree-day, or the average daily air temperature as degrees in excess of
10°C ([(maximum temperature + minimum temperature)/2]-10°C) summed over a
month-long period, and
P
is the amount of precipitation (mm) accumulated during
the same month. Commonly, 10°C is used as the base temperature to calculate agri-
cultural growing degree-days. The CSI has been correlated with wheat yields and
