3,703. Planting Unintentionally

Hilchos Shemittah v’Yoveil 1:12

If someone plants during shemittah, he must uproot what he planted regardless of whether he planted it intentionally or unintentionally. This is because Jews are suspected when it comes to the prohibitions of shemittah. If one who planted unintentionally was permitted to keep what he planted, one who planted intentionally would simply claim that he did so unintentionally.

Hilchos Shemittah v’Yoveil 1:13

If someone plows, weeds or fertilizes his field during shemittah so that it will be better for planting the following year, he is penalized and may not plant it the next year, nor may he lease it to others. Rather, he must leave it fallow. If he dies, his son may plant in it.