Many farmers who invested in the equipment needed to make the switch from synthetic to organic fertilizers and pesticides feel that it would be too expensive to resume synthetic farming at this point.

Argument; 

Many farmers who invested in the equipment needed to make the switch from synthetic to organic fertilizers and pesticides feel that it would be too expensive to resume synthetic farming at this point.  But studies of farmers who switched to organic farming last year indicate that their current crop yields are lower.  Hence their purchase of organic farming equipment, a relatively minor investment compared to the losses that would result from continued lower crop yields, cannot justify persisting on an unwise course.  And the choice to farm organically is financially unwise, given that it was motivated by environment rather than economic concerns. 

Answer;  

The argument that organic farming farmers invested in decreases crop yields omits some important concerns that must be addressed in order to assess the validity of this argument. 

Primarily, the author does not specify how much more expensive to purchase organic fertilizers and pesticides than synthetic ones.  According to the argument, going back to synthetic farming costs too much.  If the difference of investment, however, between synthetic and organic pesticides were just a small amount of money, it wouldn't be too expensive.  Without specific figures, readers cannot assess whether the investment is too expensive or not. 

Another factor ignored by the argument is crop yield.  As well as the first issue, the author must clarify how much lower crop yields get since organic farming is applied in order to measure return on investment in switch from synthetic fertilizers.  While the argument says that investment in organic farming is relative minor compared to the losses of crop yields, there is no way to know how much lower crop yields are. 

Also, organic pesticides and fertilizers are pointed as causes of lower yields.  That is not the case.  Various factors fluctuate agricultural harvest; for example, this year when farmers start organic fertilizers might suffer from severe weather such as drought or heavy rain.  Unless other conditions are assessed, it is too early to determine that organic farming triggered lower crop yields. 

Finally, this argument is not convincing because of unclear number of farmers to be assessed.  The author mentions about many farmers who invested in organic farming.  However, specific number of farmers the author asked must be mentioned, otherwise, it is too objective to claim a statement.  Subjective specific numbers must be shown to be convincing as an argument. 

In conclusion, the argument in current form is not convincing.  In order to better evaluate the author's claim, more information is needed.  To begin with, the amount of investment in organic farming must be specified.  Also, the author needs to show how much lower crop yields got compared to synthetic fertilizers and pesticides.  Additionally, other possible factors caused lower crop yields must be considered.  Finally, the condition of this assessment is not clear.  How many farmers are subjected to this research?  Before any conclusion is made, all possibilities must be discussed.