What does 'simple' mean in the following context?

Question

I met with this question while doing SAT reading,

But change the conversation to food, and suddenly efficiency doesn’t look so good. Conventional industrial agriculture has become incredibly efficient on a simple land to food basis.Thanks to fertilizers,mechanizationandirrigation, each American farmer feeds over 155 people worldwide.

The answer gives 'straightforward' as the best definition,but I still can't wrap my head around it. Actually I feel confused about the whole second sentence. What does it mean?

Answer 1

It would mean "basic."

"Land to food basis" is comparing how much land is used and how much food is produced on that land. A lot of food grown in a small area = good.

Answer 2

It is an extraneous word that does not modify the thought. It probably is intended as a synonym for "basic," but a basis is basic by definition.

The whole sentence would be a lot clearer expressed as

Industrial agriculture has become incredibly efficient in terms of food produced versus land used.

Answer 3

I'll answer this by analysing the grammar rather than the vocabulary.

Original:

Conventional industrial agriculture has become incredibly efficient on a simple land to food basis.

Explanation:

In English we can have a list of adjectives qualifying a single noun, e.g. "the big red ball"

land-to-food is an adjectival phrase that qualifies basis.

simple is an adjective that qualifies basis.

Thus:

simple land-to-food basis

(Adj) (Adj phrase) (noun)