Agriculture Reference
In-Depth Information
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Graphs by Rice Varieties (1-6)
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Nitrogen Fertilizer
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Figure 6.6
Graphic output of fertilizer effect on yield for each of six rice varieties.
common and often required by refereed publications where two or
more years of data are expected.
Evaluation over seasons is a case where the season variable is con-
sidered a fixed effect. In temperate climates, spring tends to be warm-
ing with increasing day length, while in the fall temperatures tend to
fall and days get shorter. In tropical climates, the temperature or day
length differences may not be that important, but there usually are
seasonal differences often with wet and dry seasons. Although the
specific conditions may change from year to year, the overall differ-
ences in seasons remain the same, or in statistical parlance, they are
fixed (Table 6.3).
Open the file Pumpkin Seasons.dta, which is a dataset of variety
trials conducted in the spring and again in the fall. Pumpkins are
highly susceptible to a number of potyviruses that are particularly
severe in the fall when aphid (insects that transmit the virus) pop-
ulations peak. These trials were to evaluate a new variety, Orange
Bulldog, which is resistant to many of these viruses. Enter the follow-
ing command and see the results:
 
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