In any case, once you've found your mean and standard deviations, you can make a judgment about which variety is better. All else equal, the farmer would probably prefer the variety that has a higher mean yield (more is better!). Also all else equal, the farmer would probably prefer the variety that has an output with the lowest standard deviation (because he prefers to have a crop that is predictable, rather than one that varies a lot).
So if one variety has the highest mean AND the lowest standard deviation, the farmer would clearly prefer that variety. If one variety has the highest mean while the other variety has the lowest standard deviation, it's harder to know what the farmer would want until you know whether he is a risk-loving guy or whether he likes to play it safe.
Hope that helps!