Shekalim, Chapter 1, Mishnah 2. The previous Mishnah concluded that on the fifteenth of Adar the court would send out agents and representatives to inspect the fields and see whether kilayim (forbidden mixtures) had been removed. Our Mishnah discusses what the court's agents would do with the kilayim they found.
Three stages in dealing with kilayim, as Rabbi Yehudah describes them:
"Barishonah hayu okrin umashlichin lifneihem" - at first the agents would uproot the kilayim, remove them from among the other types of produce and vegetables growing in the field, and throw them down in front of the owners of the fields.
"Misherabu ovrei aveirah, hayu okrin umashlichin al hadrachim" - when the number of transgressors increased, the practice was changed. The Yerushalmi explains that the field owners were actually pleased with the arrangement: their fields were being weeded for them, and the vegetables that the court's agents uprooted were fed to their animals. The court's agents therefore began uprooting the kilayim and throwing them onto the roads, so that they would not remain in the owners' fields but would instead be acquired by others.
"Hiskinu shaaf mafkirin kol hasadeh kulah" - even this did not solve the problem, since the field owners were still pleased: although they no longer benefited from the produce that was uprooted, at the very least they gained fields that had been weeded for them. Therefore an enactment was made that if kilayim were found in a field and were not dealt with, the entire field is declared ownerless, and anyone who wishes may come and take the produce in it.
Which kind of kilayim is being discussed?
The Mishnah must be referring to kilei zeraim, a mixture of vegetables, and not to kilei kerem. Kilei kerem are forbidden to derive any benefit from, and one may not make any use of them at all. Here, by contrast, the discussion concerns a mixture of vegetable products alone, and therefore once the kilayim were removed, it became permitted to benefit from the produce grown in the field and to make use of it.
In summary: in this Mishnah we learned the three stages in the way the court's agents dealt with kilayim found in the fields: uprooting and throwing them down before the owners, uprooting and throwing them onto the roads, and finally declaring the entire field ownerless - all because each earlier enactment turned into a benefit for the field owners rather than a deterrent from the transgression. We also established that the Mishnah is speaking of kilei zeraim, from which benefit is permitted once the kilayim have been removed, and not of kilei kerem, from which no benefit may be derived.