Although we have learned that someone who lives or works on land for three years can claim to have a ḥazaka (presumption of ownership) – he will no longer need to produce a document showing that he bought the land, since his presence on the land for three years with no objection from the owner will serve to support his claim of purchase – our Gemara lists a number of exceptions.
Rav Yehuda taught: Someone who claims to have worked land that is outside of the fenced-in area that is planted cannot claim to have a ḥazaka, since the owner can say that he did not bother to object to someone who used the area that was left for wild animals to eat from.
Rav Yosef taught: Someone who harvests grain before it ripens cannot claim a ḥazaka. The Rashbam explains that by harvesting it early he makes us suspicious that he is trying to make off with whatever he can take from the land. Others explain that the true owner can claim that he did not notice that the field was being worked, since the grain was not left until the normal harvest time.
Rav Naḥman taught: If the produce of a field was equal to the investment in it, there is no ḥazaka, since the owner can claim that he did not mind that someone else worked his field, since it did not turn a profit.
A baraita taught that someone whose claim to a ḥazaka of three years included time that the trees were orla – during the first three years after trees are planted no benefit can be obtained from their produce – or that the Sabbatical year fell out during that period, when the fruit cannot be commercially harvested by the owner, or if the field was planted kilayim – with a forbidden mixture of crops – the ḥazaka does not count. The Rashbam explains that the owner does not feel a need to make a complaint when the squatter is not making normal use of the field.
Rabbeinu Ḥananel had an alternative reading of this baraita, according to which these cases would create a ḥazaka. Tosafot explain that even under these circumstances the squatter may be deriving permitted benefit from the field, e.g. using the branches of the trees during the years of orla, so the owner must register a complaint. The Rambam rules that even if the squatter made use of forbidden fruits, still the ḥazaka would apply, since he did derive benefit from the land for three years.