Yes but the increase in agricultural production directly led to an increase in trade. People could afford to specialize when the immediate risk of famine was abated and Europe could begin to produce exportable quantities of wine, iron, cloth and grain, as well as support the merchant class which dealt in them.
That's the second phase. As the question was how to launch the process, the most easy solution is to make the nobles interested in a better production as OTL.
Higher productivity meant more profits hence the incentive to invest in better means of production. This first culminated in the high middle ages, then post black death, the Renaissance.
I'm sorry but no. It's clearly the need of nobilty to have as goods it have during the gift-microeconomy phase that launched the post-carolingian agricultural revolution.
First the investment in both trade and agriculture (i insist on that, before 850's, the domains had a stagnant production, and almost no innovation) came from the 750-850 results of raids in all western Europe not because of a first improvment of production.
Second, the investment was not made so in new techniques, for agriculture, but in the regroupment of peasants and the fusion of their diverses statues (free, serf, chased slave) into one with a rationalisation of existing techniques.
For the
pre-Plague movment (with both nex techniques including artisanal ones, wood cutted etc) i would more agree, critically because it launched the monetarization of feudal system with the development of cens. But again, it was less because of previous improvment between the X and XII than a pauperisation of nobilty and the fear to be outed from the dynamism in urban centers (except in southern France where nobility participed from the beggining to it).
So, for a Middle-Ages POD, as in "feudal", it would need that investment in agriculture is more easy and rentable than raid.
I think we are in a chicken/egg situation. Water wheel and wind mills require both a fairly considerable knowledge base as well as the financial means to construct them. One arguably needs the ideal level of development, combined with a demographic situation where said investment would be more profitable than using more human or animal labor.
Watermill exist since Roman Times. The knowlegde never really disappeared. It actually be more used with the fusion of peasantry statues in the IX and the post-carolingian agricultural revolution. I can't call that an innovation or a discovery but a rationalisation thanks to widespread of roman texts during carolingian times.
For the windmill, maybe by making it caming from Al-Andalus rather than England would make gain maybe 200 years. But without a moving base, watermill would be preferred anyway in the region with rivers.
As for Crops, Al-Andus and Islam were a major factor for introducing both to Europe. The earlier the spread the better in my humble opinion.
Well, it was recently disputed with really strong arguments. Many crops or even irrigation techniques we belived caming by Islam were present in Visigothic Spain as well.
The difference was again the rationalisation of agriculture after 70 years of civil war and the impossibility of real raids after 770's (the piracy lasting until 1000 being mainly a slavery-based one).