Tosefta sobre Terumot 6:6

How is this done [i.e, what rules apply to the taking of terumah from the same species]? We do not take terumah from the new on behalf of the old (Ter. 1:5), we do not take terumah from this year's produce on behalf of last year's produce (see Ter. 6:6), but in a field that grows two crops (i.e., early and late fruits) in [the same] year, and so too an irrigated field, we [may] take terumah and tithes from one on behalf of the other. [With respect to] vegetables picked on the evening preceding Rosh Hashanah [but which remain in the field], until the sun rises, he may return [and take terumah and tithes from] those picked [vegetables], but once the sun rises, we do not take terumah and tithes from one on behalf of the other because [once the sun rises on Rosh Hashanah, vegetables collected thereafter] are "new " and [vegetables collected previously] are "old" (i.e., from the previous year). [Note that Rosh Hashanah is the new year for tithing vegetables, see Rosh Hashanah 1:1.]