The Mishna on today’s daf discusses the case of a sharecropper who agrees to work the field in exchange for a certain percentage of the harvest, and finds that the field does not produce enough to make it worth his while. According to the Tanna Kamma, if it will produce enough to make a keri – a pile of grain – he is obligated to work the field. Rabbi Yehuda rules that if it will produce the amount of grain that he used for seed, he will have to work the field.
In offering a practical definition for Rabbi Yehuda’s ruling, Rabbi Ami quoted Rabbi Yohanan as teaching that for a field to yield a kor (a measure of volume equivalent to 30 se’a), four se’a was needed for planting; Rabbi Ami himself said that for a field that size eight se’a was needed. An elderly man explained this discrepancy to Rav Hama son of Rabba bar Avuh by telling him that during Rabbi Yohanan’s time the land of Israel was fertile, but during Rabbi Ami’s time it had become barren.
There is much evidence in the Gemara – particularly in the Talmud Yerushalmi – that the fertility of the land of Israel dropped precipitously during the period of the amora’im. We find that even during Rabbi Yohanan’s time – in the first generation of amora’im – he mentions a change in the land’s produce. This stemmed, apparently, from a worsening of economic conditions in the Jewish community in Israel, which led to improper use and maintenance of agricultural land at that time. This led to overfarming the land, whose consequence was a drop in its ability to support crops.
The Gemara also mentions two different methods of farming – mapolet yad (hand seeding) and mapolet shevarim (seeding with oxen). Mapolet shevarim made use of a mechanism that held seeds and was attached to the plow so that the seeds were distributed directly as the plowing was done. While this method saved time and effort, a much larger amount of seeds was needed in order to reach the same level of produce as planting with the mapolet yad method.