How much did the livelihood of the Rohirrim rely on agriculture?

Question

The Tolkien Gateway says they were "herdsmen and farmers".

Tolkien described them as "still partly mobile and nomadic people of horse-breeders" (Letter #297), so I guess they at least became partly settled. But the only description I can find of their farms and crops in the books is:

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Where is the spring and the harvest and the tall corn growing?
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Thus spoke a forgotten poet long ago in Rohan, recalling how tall and fair was Eorl the Young, who rode down out of the North
-- The King of the Golden Hall

Apparently they were used to farming even in the era of Eorl.

Are there more descriptions of the economy of Rohan? Their villages, their crops, their diet?

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Some context for "partly mobile and nomadic":

Rohan. I cannot understand why the name of a country (stated to be Elvish) should be associated with anything Germanic; still less with the only remotely similar O.N. rann 'house', which is incidentally not at all appropriate to a still partly mobile and nomadic people of horse-breeders!

Answer 1

The only relevant quote I can think of from LoTR itself is from Book 3, Chapter 7, Helm's Deep, where Théoden regrets that Saruman's army is burning the countryside behind them:

‘They bring fire,’ said Théoden, ‘and they are burning as they come, rick, cot, and tree. This was a rich vale and had many homesteads. Alas for my folk!’

This hints that at least in that part of the Mark the population is mainly settled in farms. (A rick is a haystack, apparently.)

Answer 2

In a word, the livelihood of the Rohirrim relied on agriculture "wholly" or perhaps "totally" and to what are you comparing that? Hunting-gathering?

Nomadic life has almost nothing to do with the Rohirrim and less with Rohan. Consider not Éomer and his riders but rather, Éowyn and Théoden.

The best example of real-life people to look into is something like Old English or Anglo Saxon, for the reason that so many books-worth of scholars state that as a fact, with intricate details, that whether I remember Tolkien himself saying so matters not.

The major difference there is that, broadly, Anglo Saxons were not horse but foot soldiers, as seen in the tragedy of Hastings.

If "did they herd horses only? What food could they possibly consume?" means "did they live by eating from horses, as some African tribes live on cattle-milk and blood?" then no; not unless you're hiding some evidence.

The details in LotR show "herdsmen and farmers" to be the key phrase "still partly mobile" to refer to the horse soldiers greatly more than to the whole people, and "nomadic" to be something of a fleeting thought; perhaps a harking back to their ancestral roots.

Broadly "herdsmen and farmers" suggests they lived by herding various livestock while "a people of horse-breeders" suggests they lived to breed horses; there being all the difference in the world between "living by" and "living to".

"Herded livestock" might be cattle or goats, sheep or even poultry but never horses.

"still partly mobile" most obviously refers to the fact that the dangerous times in which they live provide a perfect excuse for Rohirrim horse soldiers to spend their lives riding around the country, taking with them whatever is needed… and for the whole people to up sticks and travel, at need.

Who hopes to compare their lifestyle to that of the Mongols or even Scythians, please show how.