Irrigation, fertilization, and pruning during shemitah
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I have three questions about shemitah:
1) Can we use a fertilizer dispenser connected to a computerized irrigation system to release fertilizer to perforated planters with fruit trees and ornamental plants, such as roses and other perennials, growing under the open sky?
2) Is it possible to water plants as much as we desire, employing an irrigation computer, beyond the minimum needed to keep the plant alive?
3) Pruning: Is it permissible to prune roses, grape vines, citrus trees, and other flowering plants such as petunias, geraniums, etc. during the shemitah year? Failure to prune or trim certain plants can cause damage. It is not always sufficient to perform deep trimming before shemitah. Pruning and trimming are required all year round, such as with roses and grapevines. Petunias might not produce flowers and can even wilt. What should I do?
Your first two questions relate to the fundamental question of whether it is permitted to perform forbidden agricultural activities indirectly (gerama). This question is disputed among the posekim with regard to the definition of the positive injunction of veshavtah ha’aretz, “and the land shall rest;” namely, if it is incumbent on people to avoid working the land to allow the land to rest (as a personal obligation, gavra) or if the injunction entails ensuring that the land rests (relating to the object, cheftza: the land).
The practical implications of this dispute concerns whether or not gerama is permitted. Activities such as irrigation and fertilization are rabbinic prohibitions. They are prohibited since they enhance plant growth, and it is immaterial if the action is performed indirectly; at the end of the day, the act encourages growth. For this reason, optimally you should avoid fertilizing or watering more than necessary, even indirectly through a computer system. However, it is clear that if the act is done indirectly, it is not as severe and it can be permitted in extenuating circumstances only.
As an aside, it is important to make all necessary preparations before the onset of the shemitah year. If we fertilize sufficiently, especially if we use slow-release fertilizers, no further fertilization will be necessary.
Addition as of Tammuz 5781: following further discussion among the rabbis of Torah VeHa’aretz Institute, it was decided that it is permissible to use fertilizer that was loaded into the computerized system before the shemitah year. However, it will be forbidden to add new liquid fertilizer to the system during shemitah, except in extreme cases where lack of fertilizer will cause the plant to die.
As for pruning grapevines: zemirah is one of the agricultural activities explicitly prohibited by the Torah, so we certainly may not prune grapevines during the shemitah year. However, pruning that is not intended to encourage fruit growth, but rather to remove an entire branch that can cause damage unless pruned, is permitted during shemitah.
As for roses and other flowers and plants: we may not prune to spur a new flowering season. Pruning is only permitted when it would prevent significant damage to the plant if left unpruned.
It is extremely important to prepare grapevines, citruses, and ornamental plants ahead of the shemitah year, and to perform all necessary pruning so that only very minimum pruning will be needed; that is, when without the pruning the plant will be significantly damaged.