Al pi dereh ha’teva, land should be least fertile in the year just before shemitah, after it has been farmed for six straight years without rest. Yet, the Torah says that davka in that sixth year the land will produce a greater abundance than usual in order to provide enough food to last through the shemitah year. This proves, says the Shem m’Shmuel, that the land of Eretz Yisrael does not follow the normal laws of nature. It’s all hashgachas Hashem.
According to many meforshim shemitah is a lesson in bitachon. It’s one thing to skip work for one day of Shabbos, like we all do – it’s quite another thing to take an entire year off. Ramban comments on the pasuk, “Ki tomar mah nochal ba’shanah hashevi’is…” that the pasuk is mesuras, the phrases are out of order. The meaning is not, “When you ask, ‘What shall we eat in the seventh year?’” as during the seventh year there is plenty of food left from the sixth year -- there is no mystery about what to eat. The meaning of the pasuk is, “When in the seventh year you ask, ‘What shall we eat [in the upcoming eighth year]?’” Since you can’t plant in the seventh year, there will be no leftovers for year eight. The bracha, according to Ramban, is that the food from year six will last even until then.
R’ Shimon Sofer explains the pasuk k’peshuto, without reversing the order of the phrases. Even though the farmer’s storehouse is fully stocked for that seventh year, he still feels he can't eat anything because if he does, he will have nothing left for year eight. "Mah nochal...?" right now, in year seven, even though the fridge is full, because if it's eaten now, what will be left for the future?
That's how many of us go through life (es chata'ei ani mazkir). We are so nervous about the future, so worried about what will be, that we can't enjoy the bracha of what we have in the present moment. It's human nature to be concerned about the future, to fear uncertainty, but it has to be balanced with bitachon as well.
There is a famous Noam Elimelech that asks why the bracha of "v'tzivisi es birchasi" for the sixth year to produce such a bountiful harvest is couched as a response to the question of "Mah nochal...?" Why does the Torah not just tell us that Hashem will give a bracha in year six? The N.E. answers that Hashem would give the bracha automatically, but by asking, "Mah nochal..?" and showing a lack of bitachon, the farmer jeopardizes it. He doesn't really deserve the bracha anymore. Nonetheless, Hashem overrides the normal outcome and in this case, "v'tzivisi es birchasi" despite the lack of merit.
The N.E. demands a very high level of bitachon. To not even worry, to not even b'chdrei ha'lev ask, "Mah nochal...?" is hard. The Chasam Sofer has a more positive spin to the pesukim. A normal person wants to earn his living and not live on handouts. There is an idea of "nahama d'kisufa," an embarrassment in doing so. "Mah nochal..." reflects that attitude -- if we don't work, what will we eat? We don't want a handout. Hashem could just as easily do a miracle and provide food during the shemitah year for the farmer without the land being worked at all. But since we want to earn our own keep, Hashem does us a chessed and allows us to do so. "V'tzivisi es birchasi" in year six, when the farmer does have the opportunity to farm the land, to work, so that he feels he has a hand in producing something, in earning the bread on his table.