2b: One or Two?

The Gemara here goes off into an interesting tangent about weeding and watering seeds on Shabbat. Everyone agrees that these two acts are assur on Shabbat, but the question at hand is why? Rabbah thinks they are a derivative of horesh (plowing), while Rav Yosef holds that they are a derivative of zoraya (sowing). As they fight it out, Abbaye raises an a good point. He wonders why it can't be both? Why can't weeding and watering be prohibited because they are acts of both horesh and zoraya? He even quotes Rav Kahana to show that one who prunes a vine on Shabbat and uses that wood he prunes off for fuel is liable for both notaya (planting) and kotzer (reaping). The sugiya ends on this kashya.

Albeit a different situation, but this debate reminds me of the controversy around saying "Magen Avraham v'Sara" (or any of the many combinations offered) in the Amida with the ema'ot. There are those who say that the hatima of a beracha must be singular and echo the theme of the what came before it. However, it is easy to point to hatimot in our siddur that have multiple subjects ("m'kadesh yisrael v'hasmanim" etc.) It would seem, if this argument were to follow our sugiya, that here we would end on a kashya. But of course in each case the debate continues - with most Rishonim ruling in our sugiya like Abbaye, that one can be liable for both horesh and zoraya - as well as those today who rule that one may have two subjects in the hatima.