Q20 - The advent of chemical fertilizers led the farmers

[mshinners]

Question Type:
Necessary Assumption

Stimulus Breakdown:
Chemical fertilizers caused abandonment of "green-manure" crops caused soil structure to degrade. Therefore, to improve soil, ban chemical fertilizers!

Answer Anticipation:
Necessary Assumption questions tends to have weaker answers unless the conclusion is strong (my rule: the correct answer will be at most as strong as the conclusion). Here, the conclusion is rather extreme (""need to abandon""), so the answer might be stronger than I'd usually expect.

Extreme conclusions also generally lead us to the flaw by analyzing the extreme nature. Here, the author wants to completely abandon the use of these fertilizers. While it seems as if they're in some ways damaging, maybe the issue can be fixed without abandoning the chemical fertilizers.

In this case, these fertilizers are damaging because farmers who use them don't do this other thing ("green-manure" crops). It's possible that farmers could be convinced to use chemical fertilizers sometimes and green-manure crops others. The author discounts this possibility, though, and treats the situation as if you have to pick one or the other. The correct answer will probably connect chemicals and alfalfa in this mutually-exclusive manner.

Correct answer:
(E)

Answer choice analysis:
(A) Too specific. The argument relies on growing a "green-manure" crop such as alfalfa, but it doesn't have to be alfalfa.

(B) Out of scope. The argument doesn't have "green-manure" crops and chemicals being used at the same time, so a discussion of one having an affect on the other is out of scope.

(C) Out of scope/degree. First, the argument only talks about soil structure, not soil quality. Second, the argument only relies on soil structure being a significant factor, not the most important factor.

(D) While this answer choice helps the argument, it isn't necessary for the argument to work. The negative impact could be either direct (as this answer states) or indirect (as the argument establishes) to reach the conclusion, so neither option is necessary.

(E) Bingo. This answer choice states that farmers won't grow the "green-manure" crops if they're still using chemical fertilizers. That's a necessary connection to argue for the complete abandonment of their use. If we negate this answer (and it's a tricky negation) - Abandoning chemical fertilizers isn't necessary to growing green-manure crops - it kills the argument by stating the problem can be fixed while still using the chemicals.

Takeaway/Pattern:
My explanation of (E) is intentionally light on the negation of it. Spend some time trying to figure it out before reading on!



(D) translates conditionally to: If they don't abandon chem fert, then they won't grow alfalfa. Contrapositive: If they're growing alfalfa, they abandoned chem fert. In other words, abandoning chemical fertilizers is necessary for the growing of green-manure crops. The negation of that statement is abandoning isn't necessary.

#officialexplanation

[pewals13]

Got confused on this one because of the conditional language.

Here's what I got:

Advent of chemical fertilizers ------> abandon "green poop" crop --------> soil structure poor

Therefore:

Improve soil structure-----> NOT chemical fertilizers
(this can be seen as the contrapositive)

Answer choices:

(A) NOT chemical fertilizers (most) -------> alfalfa

Does not need to be assumed, think of the contrapositve

NOT soil structure poor----->NOT abandon green manure crop------->NOT chemical fertilizers

(B) The fertilizer could have one positive effect on alfalfa and not destroy the conclusion that soil structure improvement requires abandoning the use of chemical fertilizers

(C) "Most important" is almost always universally wrong on necessary assumption questions. Also, soil quality has nothing to do with the conclusion, stay focused on its precise wording.

(D) Tempting, but it doesn't have to be true. Remember that the stimulus has already told you that the lack of rejuvenating manure was the reason the soil structure suffered in the first place. Abandoning chemical fertilizer might be necessary for the reintroduction of the manure (it is based on our conditional statements)

(E) Grow green manure (many)-------> NOT chemical fertilizers

According to the contrapositive this MUST be true

[johnlwolf91]

I struggled between A and E for this question. In review, I think a simpler way to rule out A would be that it refers only to alfalfa. According to the information in the question, "green-manure" crops, SUCH AS ALFALFA, restore soil structure, but it does not have to be alfalfa specifically. Therefore, the farmers need not grow alfalfa specifically, as A suggests and instead need only to grow green-manure crops of any type, as E suggests.

[jones.mchandler]

I'm still having some issues with D...

If we negate D, it reads that "chemical fertilizers themselves do NOT have a destructive effect on the soil structure of farm fields."

The stimulus states that farmers abandoned growing green manure crops with the advent of chemical fertilizers, and as a result, the soil structure in the fields is poor.

The conclusion is that to improve soil structure, farmers will need to abandon the use of chemical fertilizers.

It seems to me that there are two gaps in the stimulus: the degradation of the soil structure could have resulted from the absence of the green manure crops, or from the use of chemical fertilizers. It seems that either one of these things separately could have caused the degrading quality of the soil structure.

With the conclusion being that in order to improve soil structure farmers need to abandon the use of chemical fertilizers, this seems to imply that the chemical fertilizers were in fact the cause of the soil degradation, and that it wasn't the absence of the green manure crops.

With that in mind, D seemed to fit the bill pretty well. Because if chemical fertilizers do not have a destructive effect on the soil structure, then why would farmers need to abandon the use of chemical fertilizers?

Please advise.

[maryadkins]

First off, thanks for the great conditional logic explanation!

And the point about the Alfalfa being an issue in (A) is a good one, too. Well done.

Now on to questions...

t seems to me that there are two gaps in the stimulus: the degradation of the soil structure could have resulted from the absence of the green manure crops, or from the use of chemical fertilizers. It seems that either one of these things separately could have caused the degrading quality of the soil structure.

Not really. We're told that chemical fertilizers led them to abandon the green manure and AS A RESULT the soil structure blah blah blah...this can most reasonably be interpreted to mean the loss of the green manure is the problem. What you suggest COULD also be true but the argument certainly doesn't assume that the chemicals themselves are what is harming the soil.

[gabcap1]

I'm still having some issues with D...
The conclusion is that to improve soil structure, farmers will need to abandon the use of chemical fertilizers.

So I've also been scratching my head quite a bit with (D), because the negation is oh-so tempting.

I think another way to approach it is to really emphasize that the author is looking to "significantly improve the soil structure." If we negate (D), "chemical fertilizers themselves DO NOT have a destructive effect on the soil structure of farm fields," I think there's a case that, just because they don't hurt the fields doesn't mean that taking them away will actively improve the fields. Removing the fertilizers may just bring the fields to a neutral level, but the author seems to want more than that because "rejuvenating" and "improving" are different from "stop destroying." That is where the emphasis on a green-manure crop comes in, it has that value-added, positive effect.

Let me know what you think.

[christinachenn]

After reviewing this question a second time, I arrived at the right answer by remembering to accept the premises as given (in this case, the premises lead to the others in the form of causation).

CM- "chemical fertilizers"
GM- "green manure"
SS- "soil structure"

Premises:
CM -> ~GM -> decrease in SS
Conclusion:
~decrease in SS -> ~CM

It seems that the author arrived at his conclusion from a contrapositive of the premises statements. When I looked at this, I realized that he skipped over the connection to GM, namely that ~decrease in SS -> GM -> ~CM. The missing piece is that GM would be used.

Initially, I was also a bit tripped up because I was in the habit of verifying correct answer choices to necessary assumption questions by negating them and see if they attack the argument, but I eliminated answer choices in this question without having to do that. Do MLSAT instructors agree with this?

Answer choices:
(A) most who -CM -> alfalfa (GM)
The two issues that are wrong with this are, as the above people have mentioned, 1. alfalfa does not equal GM, and 2. this seems to be a reversal of what is implied in the conclusion which is GM -> -CM

(B) the two issues with this are 1. the stimulus talks about using CM and abandoning GM, whereas this choice talks about applying CM to GM, and 2. a positive effect on growth doesn't necessarily equal a positive effect on soil structure.

(C) I eliminated this once I saw "most important factor" and also "soil quality."

(D) This is a tricky answer choice and I chose it when I initially took this test. The incorrectness of this answer choice lies in realizing that the conclusion jumped over/implied that GM would be used to increase SS. It isn't required that chemical fertilizers themselves are bad for soil structure because the argument tells us that the absence of GM led to bad soil structure. Also, by the word "themselves", there seems to be an implication that CM directly leads to SS which is not quite true.

(E) Many will grow GM -> ~CM
This matches the missing piece in the conclusion!

I'm not sure if I had reasoned these answer choices out correctly and would appreciate a review by an MLSAT instructor. Thank you!

[contropositive]

I thought a lot about this argument and still couldn't figure it out even from the explanations above. I initially picked D but after some thinking this is how I think one can arrive at the right answer E.

The argument is saying farmers replaced (green manure) GM with (chemical fertilizer) CF . AS A RESULT OF abandoning GM, soil structure became poor. Therefore, in order to improve soil structure again they need to abandon CF.
Contropositive: If they do not abandon CF then they will not improve soil structure, which means they won't be using GM. This is what answer choice E is saying. After all, it was the result of abandoning GM that caused the poor soil structure. So its implying GM is responsible for whether the soil structure is poor or not.

I think D can be thought of as premise booster because we were explicitly told that "as a result [of using CF], the soil structure became poor" this is what D is restating to us.

As for the other answer choices, I think if you really have a good grasp of the argument core, then you should easily be able to eliminate A - C.
A) alfa is just one type of green manure. Who really cares what type they will grow...they could grow other types of green manure. out of scope.
B) we were never concerned about growth. out of scope
C) soil quality is out of scope

[phoebster21]

I'm still having some issues with D...
The conclusion is that to improve soil structure, farmers will need to abandon the use of chemical fertilizers.

So I've also been scratching my head quite a bit with (D), because the negation is oh-so tempting.

I think another way to approach it is to really emphasize that the author is looking to "significantly improve the soil structure." If we negate (D), "chemical fertilizers themselves DO NOT have a destructive effect on the soil structure of farm fields," I think there's a case that, just because they don't hurt the fields doesn't mean that taking them away will actively improve the fields. Removing the fertilizers may just bring the fields to a neutral level, but the author seems to want more than that because "rejuvenating" and "improving" are different from "stop destroying." That is where the emphasis on a green-manure crop comes in, it has that value-added, positive effect.

Let me know what you think.

I think that's a great point.

Is this argument (and incorrect answer choice) similar to the following analogy? When the television became a popular household item, school age children began abandoning the practice of reading books. As a result, spelling ability declined. So, to significantly improve spelling, young children must abandon the television.

The parallel wrong AC would be "the television itself has a destructive effect on the children's ability to read."

But common, really? Does the Tellyvision rallly cuase you to speel wourse? lol.

If you negate the AC, "the television itself does NOT have a destructive effect on the children's ability to read," does that WRECK the argument? Remember, the very specific conclusion of this prescriptive argument was they MUST stop TV watching all together. So even if the TV doesn't have a bad effect on spelling capabilities, (say it just does nothing, it's neutral) does that in and of itself mean that it's going to "significantly" improve spelling by eliminating it? The TV isn't hurting or harming, but that isn't necessarily improving your spelling.

[CalPoliScience2016]

Can someone clarify the first sentence in the stimulus, and whether it is making a causal claim? When a passage says, "X led Y to abandon Z," is that a causal claim or merely correlation?

I originally read this argument as a causal chain.

Chemicals -> Abandon GM Crops -> Poor soil structure

This caused me to answer incorrectly. However, upon review, I re-read it as farmers used chemicals while also abandoning GM crops. The abandonment of GM crops led to poor SS. Under this reading, it makes more sense why the conclusion "to make SS better, farmers need to abandon chemicals" is a huge jump. What do chemicals have to do with soil structure if its degradation only correlates with farmer's use of chemicals? Aha, the argument is assuming that farmers won't use GM crops unless they abandon the use of chemicals. And that is what the correct answer basically says.

But again, can someone clarify whether we should ever read "led" to mean a causal claim?

[mshinners]

But again, can someone clarify whether we should ever read "led" to mean a causal claim?

"Led" should be read as a causal claim.

[seychelles1718]

While previous posts state the direct cause of the deterioration of the soil structure is not growing green manure (which is true), I believe the argument presents a chain of cause and effect, which means the introduction of chemical fertilizers is still a cause of the poor soil structure.

Chemical fertilizer --> Abandon green manure --> Poor soil structure

So I think it is correct to say that the author is assuming the chemical fertilizer is the cause (but not the direct cause) of the poor soil structure, while it is important to distinguish this from what D is saying. D is saying chemical fertilizer is the direct cause of the poor soil. I believe if D said, "chemical fertilizers have affected the change in the soil structure", it could be the correct answer.

Can anyone please confirm if I am missing anything? Thanks!

[ohthatpatrick]

You're correct.

The distinction you're making is the same one the official explanation was making:
(indirect cause, which matches the argument):
using chem F's --> not growing green manure --> worse soil structure

(direct cause, which is what D is saying):
using chem F's --> worse soil structure

[andrewgong01]

Aside from the issue in "A" as stated in Matt's answer that it is too specific on alfalfa ,can you also rule it out this way

A is too strong because we do not need to assume that most farmers will start growing alfalfa. Maybe it is enough only for a minority of farmers to do it. In other words we don't need to assume most farmers to do it.

It is also too strong in the sense that it directly states that farmers will start growing alfalfa ( or any other crops) because it seems like to me the argument is only saying that fertilizers is PREVENTING the use of alfalfa and other green manure groups and that if we want green manure crops we can not have fertilizers.

[ohthatpatrick]

Because the conclusion is generalizing about farmers and about the "typical" soil structure in the region, I think it's fair to say that the author's conclusion is assuming "most".

(Obviously if she has to assume "most", she has to also assume "at least a minority", but I'm saying I don't think "most" is a great way to get rid of the answer)

I was confused by this thought:
" it seems like to me the argument is only saying that fertilizers is PREVENTING the use of alfalfa"


The author is assuming that using chemical fertilizers are preventing the use of green-manure crops. The argument doesn't say it. (That's precisely why E is correct)

The argument only said that "once we got fertilizers, we stopped doing green-manure cops". But that doesn't mean that the 1st prevented the 2nd.

Our big objection to this argument is, "Why do they have to abandon fertilizers? Why don't they just do fertilizers AND green manure crops?"

[MC_H3]

Hey Guys,

This is my first time posting so forgive me (and correct me) if my logic is off but I wanted to weigh in on this problem. We know that with a lot of necessary assumption questions we want an answer that will fill the gap in reasoning between P and C. With this particular problem, if you draw it out using conditional reasoning you should get A (use of chemicals) ---> -B (abandon "green-manure" crop ----> -C (soil sucks). Then it goes to conclude
C (good soil) ---> -A (abandon use of chemicals). This looks valid b/c it appears to be a correct contrapositive but there is a HUGE gap here. The conditional above is actually just a causal link and thus not a true conditional rule. So we need something that says yes this is actually a rule and not just a causal statement. So we should be able to easily prephrase the rule B-->-A (Answer choice E). This validates, to a degree, the chain link above. Another gap would have been if C ---> -B that could have been filled. I hope this helps anyone who may be confused by this problem!

P.S. If you look at Answer Choice (A), it would be written out as -A ----> B which is an illegal negation of the chain link we created above.

[EricaL584]

I struggled between A and E, but realized that even A changes from specifically "alfalfa" to "green-manure", it is still wrong.

Even if abandon chemical fertilizers CAN lead to growing green-manure, so what? Meaning we have to/need to abandon chemical fertilizer? Not necessary, because we don't know if thru other actions we can meet the same goal. I think A at most can be a sufficient assumption.

[RoyS513]

Hey guys,

I have a question with (E). I doubt if it is really a necessary assumption.

I think there's an assumption underlying (E): The only way to improve the soil structure is by growing green-manure crops.
What if there're other ways, say, using professional equipment to restore the soil structure. Then farmers do not need to abandon the chemical fertilizer.

Does that still make (E) a necessary assumption?

[TonyW1]

That's the exact reason I didn't like E at first and did not picked it. I felt it is a such bold assumption there. I am glad that been brought up. Does someone mind giving some insights? Thanks

[JoeD532]

Hi Tony!

Take my advice with a complete grain of salt, but when I go to necessary assumption questions, I immediately go to the negation test. If we try it on all the answers, I think that the correct answer (E) becomes a bit more obvious and not so bold after all.

Con: We gotta quit it with the chemical fertilizers if we want our dirt to get better.
Why: Because the fertilizers made us stop using "green-manure" crops that rejuvenated the soil.

Prediction: The author is taking for granted that if they quit using chemical fertilizers, they will grow green-manure crops like alfalfa.

With that in mind, let's get into the answers and start chopping out the bad answers using our negation test!

A) Negated, this comes out to "most, if not all, farmers in the region who abandon the use of chemical fertilizers will not grow alfalfa." Okay... that's totally fair... but what about green manure crops in general? They're not all limited to alfalfa. This answer could very well be correct if it was a sufficient assumption question, but the negation test shows me that this isn't necessary. I won't exactly give it the chop since it has alot of our prediction in it but I am very skeptical already.

B) Applying chemical fertilizers to green-manure crops has no positive effect on their growth? What does this have to do with anything? If you negate it, it does nothing to the argument. Chop!

C) Okay? So maybe structure isn't the most important quality, but it could be the second most. This doesn't destroy the argument if we were to negate it. Chop!

D) Negating this also has no bearing on the argument. It doesn't really do anything. Chop!

E) Okay, here's something I like. Negating this will destroy our argument. If farmers will grow green-manure crops (including alfalfa) even if they don't abandon the use of chemical fertilizers, then the conclusion is gone. Why would we need to quit chemical fertilizers if we can grow green-manure crops at the same time?

With that being said, you can safely eliminate A and go with E, even if it does seem a bit off the rails.