Peninah Feldman of Teaneck spent the summer toiling in the scholarship of vineyards.

The budding agronomist has graduated from Cornell’s College of Agriculture and Life Sciences and is applying for graduate school to study pest control. She recently spent a month studying at the Yeshivat Chovevei Torah in Riverdale.

This year, the Orthodox rabbinical seminary focused its summer program of intense study on the upcoming shmitta year, and opened it to non-rabbinical students. “It was a really wonderful experience,” Ms. Feldman said. “I’m really glad I was able to take a month off from my life and just do it.”

Ms. Feldman graduated from the Ma’ayanot Yeshiva High School for Girls, and studied in yeshiva in Israel for a year before Cornell. She said that “it was wonderful” to be part of the Chovevei community and the teamwork of the summer program.

The program began with the group studying the Mishnaic tractate of Shevi’it, which deals with the sabbatical year. After that, the students mostly studied on their own, delving into the thickets of topics that interested them particularly.

For Ms. Feldman, that topic was the question of pruning vineyards during the shmitta year. Pruning is one of the agricultural activities that halacha bars during the sabbatical year. “In the modern era, this has become a much bigger issue than it was, because the grape vines we have now are so vigorous that they have to pruned every year,” she explained.

Grapes grow only on newly sprouted tendrils. The next year, the tendrils turn to wood, which sends out new tendrils that will yield new grapes. If they are not pruned, the vines will produce too many shoots. That means too many grapes, which “turn out small and mushy and mealy and don’t get any of the flavors that would make good wine,” Ms. Feldman said.

That wouldn’t affect only the sabbatical year’s harvest, but the following year’s as well.

Pruning the vines before the sabbatical year begins on Rosh Hashanah only would make the problem worse. “You get an explosive rate of growth from the vine,” she said. “It wants to grow more.” That’s why pruning takes place, at least in Israel, in February, when the vines are dormant.

In her study of Jewish law about pruning during shmitta, Ms. Feldman discovered that the topic was long dormant. The Mishnah and the Jerusalem Talmud discussed the topic in the first few hundred years of the common era, while Jews still lived in the Land of Israel. After that, commentators on the Talmud discussed that discussion, but with virtually no Jewish agricultural presence in the Land of Israel for 14 centuries, the questions were abstract. That changed with the return to the land in the 19th century.

In the 1880s, after Edmond James de Rothschild helped the Jews of the First Aliya plant their first vineyards near Rishon Letziyon, the topic was no longer moot – and halachic discourse blossomed.

“I was surprised by how the Torah says you can’t prune your vines, and every modern posek” – halachic arbiter – “says, here’s how you prune your vines. I was surprised by the resourcefulness of the poskim,” Ms. Feldman said.

Different authorities dealt with the problem of permitting pruning in different ways.

Rabbi Abraham Isaac Kook, who would later become the first chief rabbi of Palestine under British rule, is famous for solving the problem of shmitta through heter mechira – permitting the land to be temporarily sold to non-Jews.

But in addition to the broad, general, and controversial solution, he also addressed the specifics of agriculture in the shmitta year.

In terms of pruning, Ms. Feldman said, “Rav Kook imagines that the Torah is only talking about pruning the very tips of branches, but the modern way, when we prune down to the bottom of the branches, is sort of a lower level of transgression and you’re able to do it to preserve the tree.”

“The Chazon Ish” – Rabbi Avrohom Yeshaya Karelitz, who led Israeli charedi Judaism until his death in 1953, and rejected Rabbi Kook’s approach – “has his own picture. He has a very complicated ruling, where he says only a professional can do a good job, and only that is prohibited by the Torah.” As a result, pruning could be done by amateurs, if they were careful to be indiscriminate about it.

“It was a very cool journey,” she said of her research, which she collated in a paper for the yeshiva’s forthcoming journal on shmitta.

Ms. Feldman came to her study with hands-on experience in shmitta research. She worked as an intern two summers working on projects for the Israel Ministry of Agriculture’s Unit for Agriculture According to the Torah.

“One of the projects was a spray that you spray on flowers of grape vines which stops them from turning into fruit,” she said. Because the flowers are so sensitive, they can be disrupted by the chemical that doesn’t harm the vine’s leaves. As an intern, she helped harvesting and weighing the grapes from the sprayed vines.

The immediate purpose of the spray was for orlah – the produce of a tree or vine’s first three years, which the Torah says cannot be eaten. “Instead of having to produce all this non-usable fruit and send in laborers to remove it, it would be much cheaper to just spray this spray and take down the yield.”

And it would have applications for shmitta: “Destroying the flowers helps the vine produce a moderate number of fruits, even if there are a lot of branches. But the best way to use it would be in conjunction with another form of pruning.”

She compared her interest to the halachic issues of pruning to her professional interest in pesticides.

“I’m interested in giving both growers and poskim as many tools as possible to solve problems,” she said.

“There’s a lot to be said about shmitta on a conceptual level, but on a practical level, just dropping everything and walking away doesn’t work. In the Torah, God says, ‘I’m going make you miracles and you’ll be able to eat all your stored food from before shmitta.’ I don’t think we live in a world where God is going to give us miracles for our economy to function.”