Q18

[alovitt]

I chose A, and I still don't get why E is correct. In the first paragraph, it says crop rotation denys pathogens a suitable host for a period of time. Thus, moving crops around (crop rotation), makes them hardier and more resistant to disease because the pathogens are unable to attack them as frequently. E was automatically eliminated when it made reference to different plant "species." Where in the passage does it suggest that certain plant "species" are more prone to attack? Certainly some plants are more prone to attack than others (the ones that are not rotated), but how are certain species more or less suitable?

[timmydoeslsat]

The idea of crop rotation is when you grow different types of plants in a section of land so as to avoid what was discussed in the passage.

So, if we have plant A in this land that is showing decreased yields of what it was once producing, we may think that the phytopathogens are playing a role in causing this.

According to the passage, by rotating crops, we would be denying those pathogens a suitable host. This allows us to infer that phytopathogens can attack some species of plants while finding others to be unsuitable.

So the next time we have plant A in that land after the crop rotation, we can expect our yields to be higher with the absence of the phytopathogens. They would be gone because they could not find a suitable host during the crop rotation.

[alovitt]

OK, I think I missed the whole point about types of crops. I guess I assumed the passage may have been discussing different crops but of the same type. What is wrong with A? Does A mischaracterize crop rotation? I guess moving plants around doesn't make the plants themselves more resistant, rather they are less likely to encounter pathogens. Is that right?

[timmydoeslsat]

There is absolutely no support for us to state that moving crops around make them more resistant to disease.

We are told that crops grown in a certain tract of land will eventually lead to lower yields.

We are told that this problem can be cured by crop rotation. So by planting one type of crop in area A, and another type of crop in area B...we will not give the phytopathogens a suitable host for a period of time.

Of course, if we just switched them once and continued to cultivate them where they are now, we will still have eventual yield decreases. So we can also infer that time is a factor in these phytopathogens lowering the yield.

[maryadkins]

Good discussion and explanation. Hopefully this clarifies.

Basically, we know crop rotation helps with the decreased yields that are due to the bad bacteria. But we're not told it's because it makes the plants more resistant to disease.

[JGafnea]

The idea of crop rotation is when you grow different types of plants in a section of land so as to avoid what was discussed in the passage.

So, if we have plant A in this land that is showing decreased yields of what it was once producing, we may think that the phytopathogens are playing a role in causing this.

According to the passage, by rotating crops, we would be denying those pathogens a suitable host. This allows us to infer that phytopathogens can attack some species of plants while finding others to be unsuitable.

So the next time we have plant A in that land after the crop rotation, we can expect our yields to be higher with the absence of the phytopathogens. They would be gone because they could not find a suitable host during the crop rotation.

I'm still confused.

"The idea of crop rotation is when you grow different types of plants in a section of land so as to avoid what was discussed in the passage."

The passage doesn't say this does it? It doesn't explain the actual process of crop rotation. It just states that it involves "denying the pathogens a suitable host for a period of time." The method of denial isn't explained. I actually thought that it meant that you leave the ground unused for a period of time to starve the pathogens.

"This allows us to infer that phytopathogens can attack some species of plants while finding others to be unsuitable."

Because of the reasons mentioned above I couldn't make this inference. I thought this choice was to far of a reach.

I couldn't settle on any of the answer choices.

[griffin.811]

Not a fan of this question either! Based on the above responses, we are to assume that because one crop was rotated out of a plot of land, that another crop was rotated into that plot. This seems like a stretch to me.

What if the farmer has two plots, and only grows one type of crop and every year he changes the plot he grows that crop on to avoid the photo bacteria? It doesn't seem to be a requirement that he move another plant into the area with high photo bacteria.

The only way I see this as a suitable if we assume that crops are not the only "plants" growing on the plot. For instance, after moving the crop from one plot to the nexts, there are still weeds like grass and dandelions left behind. This seems a more reasonable assumption since it seems it would be nearly impossible to rid land of weeds without destroying the crop.

What am I missing?

[brian.howton]

Hi,

I know this is an old test and this discussion petered out a few years ago; nevertheless I'm going to take a stab at answering it.

(A) is incorrect because the text only tells us that crop rotation makes plants less susceptible to the phytopathogens that cause lower yields. Lines 7-8 say, Crop rotation '[denies] pathogens a suitable host for a period of time.' This does not imply that a the plants themselves become hardier and more resistant.

(B) can proven incorrect by looking at lines 9-13, which talks about soil becoming suppressive 'after a number of years'.

(C) cannot be supported by anything in the first paragraph, the only one of the three to discuss crop rotation.

(D) is irrelevant and therefore incorrect. Whether phytopathogens are the most or least responsible for plant disease says nothing as to why crop rotation in particular can increase crop yields.

And finally, (E) is correct, even though its tone is broad and ambiguous (if it were offered as an explanation in an agro journal, for instance, it might be rejected as imprecise); it does, however, get as close to an explanation of the five choices given. Support can be found in lines 6-8, which explains the conditions under which some plants are more and others less suitable hosts of phytopathogenic bacteria.

I hope these breakdown helps.

[pewals13]

I guess my issue with (E) is that "crop rotation" could also theoretically refer to leaving a tract of land uncultivated for a period of time, during which the phytopathogens would be unable to grow for lack of a suitable host. Because of this, I'm not sure I see it as inferrable that some plants must be unsuitable. Anyone want to let me know why I'm wrong?

Much appreciated.

[ohthatpatrick]

You're right in theory, as many others in this thread have similarly felt.

In reality, though, 'crop rotation' is by definition NOT leaving a given tract empty.

I just went to Dictionary.com and this is what it says for 'crop rotation':

crop rotation

noun
1.
the system of varying successive crops in a definite order on the same ground, especially to avoid depleting the soil and to control weeds, diseases, and pests.

So the answer is definitely accurate; what's more worthy of complaining is, "how did LSAT expect me to have the outside knowledge of what Crop Rotation means?"

Good question, but there's no good answer coming. I definitely interpreted 'crop rotation' as the definition implies, but I don't know why. I guess I had some vague idea of what it meant.

To me, even with no prior knowledge, the verb "rotate" connotes that you moving one thing and replacing it with another.

If the people sharing an apartment rotate chores, they swap.

If volleyball players are rotating after a serve, they swap positions.

If you rotate a clock or a dial, what WAS at 12 o'clock is now replaced by something else.

It seems like the other meaning people were considering was more like MOVING a crop than like ROTATING it.

No matter what, given that your only textual support is "denying the pathogens a suitable host for a period of time", you'd have to pick (E) just because it's the closest match for that language.

Hope this helps.