Models in Irrigation andWater Management - Practices of Irrigation and On-farm Water Management - page 417

1.6

1.2

0.8

y = 0.0369x + 0.7707
R 2 = 0.8435

0.4

0

0 5 10 15 20

Relative year

Step 3

Deduct the trend component from the original yield series. The yield data becomes
as follows:

Year Yield rate after deducting trend (t/ha)

1980 0.8601

1981 0.8987

1982 0.6962

1983 0.7809

1984 0.6667

1985 0.6583

1986 0.8273

1987 0.7382

1988 0.7415

1989 0.6273

1990 0.8530

1991 0.8448

1992 0.7687

1993 0.6935

1994 0.9006

1995 0.8230

1996 0.7924

1997 0.7006

Step 4

Test the dependency of the yield on weather elements one by one. Perform simple
linear regression analysis of yield and a weather element, say, rainfall.

1.0000

y = 0.0005x + 0.7518
R 2 = 0.0094

0.8000

0.6000

0 20 40 60 80