Rosh Hashanah, which begins at sundown tonight, marks the onset of another sabbatical year (shmitta) for the Land of Israel.

Indeed, no other halachic subject is fraught with more challenges for the observant Jew in Israel.

Although at first glance shmitta seems very straightforward, it is as complex as it is fascinating: "And six years you shall sow the land, and gather in the increase thereof; but the seventh year you shall let it rest and lie fallow, that the poor of your people may eat, and what they leave the beast of the field shall eat. In like manner you shall deal with your vineyard, and with your oliveyard" (Exodus 23:10-11).

Rabbinic law states that shmittat karkait — the "release" of the land, allowing it to lie fallow — is dependent on Israel's possession of the land.

Rabbinic law also forbids planting, plowing and the pruning of trees, which are logical extensions of prohibitions on sowing, harvesting, pruning vines and picking grapes. It also prohibits cleaning stones, weeding, fertilizing, hoeing, watering and other forms of agricultural activities. The produce of the seventh year that grows on its own is permitted for food. But it is considered communal property and can't be traded or used for animal food.

Shmitta observance has always been problematic. Isaiah Horowitz, a late 16th-century biblical commentator, immigrated to the Holy Land in 1621 and complained in letters how shmitta was neglected because of economic conditions.

Renewed Jewish settlement in the Holy Land in the late 1800s led not only to more widespread Jewish ownership of the land, but to the great halachic debates between the most revered Torah scholars of the generation over shmitta observance.

One century and many sabbatical yeas later, the controversy continues: Is the rabbinic heter mechira – a special dispensation that permits the temporary sale of land in Eretz Yisrael as a way of overcoming the strictures of the law of shmitta in difficult circumstances — temporary or has it become permanent?

There is growing opposition to the continuation of the heter. Spurring this opposition was Rabbi Avraham Isaiah Karelitz, who, in a paper published in 1935, rejected the land-sale solution to the problems of shmitta. He ruled that residents of the Holy Land should do all in their power and all that is legally permitted in the seventh year to utilize natural and scientific means to overcome the difficulties posed by shmitta. Karelitz helped found the Institute for Agricultural Research According to the Torah, where experiments are being made to enable farmers to observe the laws of the shmitta without incurring financial loss.

Although the Torah forbids sowing in the field — meaning an open field or an area of soil that is not covered, and where the seed is in direct contact with the soil — there are sowing-like activities that are permissible. These include, sowing or planting on a plot of land that is covered and surrounded by a wall or fence of at least 10 handbreadths in height, for this is not considered a "field" but rather a "house." Sowing in a plant pot that has no hole for drainage and that stands in a walled and covered place would also not be considered as sowing in the field, as there is no direct contact between the seed and the soil of the open field. Eventually, these young shoots are transferred to the field, together with the soil attached to them in such a manner that the roof and the fencing are not removed in the process.

Crops grown by water culture (hydoponics), using gravel, straw or sand beds are also allowed.

Since shmitta laws are considered to be rabbinic as opposed to scriptural in nature, most halachic authorities permit these kinds of indirect sowing.

Whichever way Israelis observe the sabbatical rest this year, one thing is clear: science, technology and an increased interest in observing shmitta "by the book" will make for a challenging year.