Answer #2 (Rava): Even the Chachamim (who say Shemitah is mid'Oraisa nowadays) would permit watering, although it is a derivative of either "Plowing" or "Sowing". This is because only the four things mentioned in the Torah are prohibited on Shemitah (mid'Oraisa): Harvesting (grain, etc.), Picking grapes, Sowing and Pruning. All other types of working the land are mid'Rabanan and they were lenient in cases of loss, as above, 6a.

Question on Rava: A Beraisa derives from the Torah that the following are forbidden on Shemitah: Weeding, Hoeing around a tree, Cutting (not uprooting) weeds, Pruning, Thinning branches, Supporting a tree, Fertilizing, Removing stones from soil around tree base, Covering exposed roots with dirt, Smoking out pests from leaves. So there are actually many things that are forbidden mid'Oraisa!

Answer: This derivation is only an Asmachta; all these activities are actually mid'Rabanan.

Question: The above Beraisa also specifically permits Kishkush (see below), Hoeing around a tree [in contradiction to 6c - see Rashi], Filling ditches with water, and Digging circles in the ground around the base of a vine. But another Beraisa prohibits Kishkush [and Removing stones from a vineyard]!

Answer: Kishkush can mean two things: Plugging cracks in trees, which is permitted (to prevent loss), and Hoeing to improve the tree's quality, which is forbidden.

The Amora'im argue whether or not plowing on Shemitah is punishable with Malkos mid'Oraisa.

Question: Why shouldn't one get Malkos mid'Oraisa for plowing?

Answer #1: R. Ila'a's rule: When there is a Kelal u'Perat u'Chelal, but the Kelalim are positive (here: "A Shabbos Shabbason shall be for the land") and the Perat is negative (here: "You shall not sow, etc."), it is not judged as a Kelal u'Perat u'Chelal but as a Kelal u'Perat. This means that only the four things mentioned specifically are liable to Malkos, but not other labors. The opinion that rejects Malkos for plowing agrees to R. Ila'a's rule, the other opinion disagrees.

Answer #2: Everyone disagrees with R. Ila'a's rule, but there's another reason to excuse one from Malkos: Picking grapes is derivable from Harvesting grain, and Pruning is derivable from Sowing; the Torah therefore did not have to mention these two. Since it did mention them, this shows that it is only these two derivatives (Toldos) that are forbidden mid'Oraisa, but not other Toldos. Similarly, one does not receive Malkos for Avos that are not mentioned in the verses.

Question: How can we say other Toldos are not forbidden by the Torah? There is a Beraisa (quoted above, 6c) that deduces that many other Toldos are forbidden by the Torah.

Answer: These are only Asmachta'os, as in 6d.

Rav Dimi, while in Eretz Yisrael, heard something about an "additional facet" of Shemitah, that there is a derivation from a Pasuk to teach that one is Patur for violating it. But he couldn't remember the details. Two possible interpretations are offered:

Answer #1 (R. Elazar): The "additional facet" of Shemitah is Plowing, which is seemingly prohibited because of the Kelal u'Perat u'Chelal discussed above. But in fact it is derived from a Pasuk that there is no punishment for Plowing, as above 2b.

Answer #2 (R. Yochanan): The "additional facet" of Shemitah refers to the additional periods of time before Shemitah during which agricultural labors are forbidden (orchards are forbidden after Shavu'os; wheat fields after Pesach). But there is a derivation from a Pasuk (see below, 8b2) that shows that there is no punishment for violating these additional periods.

R. Shimon ben Pazi ... says that Raban Gamliel's court abolished these additional periods.

Question: A court cannot abolish a ruling of an earlier court unless it is superior in wisdom and number!

Answer: The enactment was originally made with the explicit proviso that it could be nullified in the future.

Question: The additional periods are in fact more than a Takanah, they are (as R. Asi... said) Halachah l'Moshe mi'Sinai! How, then, could Raban Gamliel annul them?

Answer: The Halachah l'Moshe mi'Sinai forbids work only after Rosh Chodesh Elul. The early rabbis made a Takanah (with a proviso permitting future annulment) to extend this period to Pesach or Shavu'os. It was this rabbinical extention that R. Gamliel abolished.

Question: The additional periods are in fact more than Halachah l'Moshe mi'Sinai; they are derived from a Pasuk (for Rabbi Akiva derived it from: "You shall rest from Plowing and from Harvesting"). Why did R. Asi... say that it is a Halachah l'Moshe mi'Sinai?