Biology Reference
In-Depth Information
2000
1800
1600
1400
1200
1000
800
600
400
Year vs Yield (kg/ha)
Regression
200
0
1970
1975
1980
1985
1990
1995
2000
2005
2010
Year
Figure 10-1 US oilseed sunflower yields from 1975 to 2006 (USDA, National Agricultural
Statistics Service 2009).
average annual oilseed sunflower yields in the US from 1975 through 2006.
Although environmental conditions varied considerably from year to year
and affected crop production, a regression line shows that there was a
gradual annual increase in yield of about 7.5 kg ha -1 . This translates into an
increase of about 240 kg ha -1 over the 32-year reporting period. The trend to
increase yield can be expected to continue as sunflower heterotic groups
become better defined and the effects of their interactions are understood
and exploited.
The US national annual yield increase occurred despite a gradual
westward shift in production from fertile soils with adequate rainfall to
semiarid regions with less productive soil. Diseases and insect problems
were among the reasons for the shift in the production areas. However, in a
situation similar to Argentina, competition for production area by maize
and soybeans, which many producers regarded as more profitable and easier
to grow, also played a role in dislocating sunflower to the western, drier
areas of the Great Plains where sunflower with its deep taproot could thrive
better than maize or soybean. Coupled with the displacement of sunflower
growing areas in the US in the past two decades was a concomitant decline
in total production due to decreased land area planted to sunflower. This
was largely due to increased competition from canola, which has established
 
Search WWH ::




Custom Search