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发帖数: 194 | 1 研究表明只是长期单一种植，可以抗一些风险．平年并不增产．
confirms the general understanding that the major benefit of genetically
modified (GM) corn doesn't come from increasing yields in average or good
years, but from reducing losses during bad ones.
抗风险的收入相当于每英亩增产0.006% 到 2.7%.
Value of modified corn is more in reducing losses than boosting yields
（0.8 to 4.2 bushels increased per acre，１５０ bushels per acre).
"A lot of farmers assume that if it's transgenic, it's great in terms of
yield, but we know that putting a transgene into a corn hybrid isn't always
successful," says Lauer. "You don't want to pay $75 dollars more per bag of
seed to produce 12 bushels less per acre."
However, even among poor-performing groups of GM corn, there are individual
varieties that perform quite well, Lauer notes. "It depends on how the
transgene interacts with the underlying germplasm," he says. "My message to
farmers is that every hybrid has to stand on its own."
Where transgenic corn clearly excels is in reducing production risk. The
researchers found that every GM trait package — whether single gene or
stacked genes — helped lower variability. For farmers, lower variability
means lower risk, as it gives them more certainty about the yield levels
they can expect.
This makes sense, explains Lauer. "The traits themselves don't add to yield.
What they do is protect the yield, so any kind of yield advantage we can
get from [a variety of hybrid corn] will be protected from pests," he says.
Lauer equates choosing GM to purchasing solid-performing, low-risk stocks.
Just as safe stocks have relatively low volatility, yields from GM crops don
't swing as wildly from year to year, and most important, their downswings
aren't as deep.
GM crops help reduce downside risk by reducing losses in the event of
disease, pests or drought. Economists Shi and Chavas estimated the risk
reduction provided by modified corn to be equivalent to a yield increase
ranging from 0.8 to 4.2 bushels per acre, depending on the variety. |
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