Halacha

הלכה א
הַתְּרוּמָה עוֹלָה בְּאֶחָד וּמֵאָה. כֵּיצַד. סְאָה תְּרוּמָה שֶׁנָּפְלָה לְמֵאָה סְאָה שֶׁל חֻלִּין וְנִתְעָרֵב הַכֹּל מַפְרִישׁ מִן הַכֹּל סְאָה אַחַת וְנוֹתְנָהּ לַכֹּהֵן וְהַשְּׁאָר מֻתָּר לְזָרִים. וְכָל תְּרוּמָה שֶׁאֵין הַכֹּהֲנִים מַקְפִּידִין עָלֶיהָ כְּגוֹן תְּרוּמַת הַכְּלִיסִין וְהֶחָרוּבִין וְהַשְּׂעוֹרִים שֶׁל אֱדוֹם אֵינוֹ צָרִיךְ לְהַגְבִּיהַּ הוֹאִיל וְנָפְלָה בְּמֵאָה בָּטְלָה בְּמִעוּטָהּ וְהַכֹּל מֻתָּר לְזָרִים:
כסף משנה
1.
Terumah becomes nullified in a mixture 101 times the size of the original quantity.1In Hilchot Ma'achalot Assurot 15:16, the Rambam explains: Why did [the Sages] choose the figure of 100 for terumot? For terumat ma'aser is one hundredth of the entire crop, and yet it causes the entire crop to be "sanctified," as [Numbers 18:29] states: "its sacred part." Our Sages said: "An entity which must be separated from it sanctifies it, if it returns to it. Nevertheless, from Halachah 13-14, it appears that according to Scriptural Law, terumah is nullified when mixed with a majority of ordinary produce and the verse is cited merely as a support.
What is implied? When a se'ah of terumah falls into 100 se'ah of ordinary produce and all the produce becomes mixed together,2Obviously, if the produce which is terumah is distinct, it is sufficient for him to remove it. he should separate one se'ah and give it to the priest. The remainder is permitted [to be eaten by] non-priests.3In Hilchot Ma'achalot Assurot 15:15, the Rambam explains: "Why is it necessary to separate [a measure of] terumah and not a measure of orlah or mixed species from a vineyard? Because terumah is the property of the priests." I.e., from a ritual perspective, it is not necessary to remove the se'ah, for the existence of the terumah has been nullified. Nevertheless, from a financial perspective, it is necessary to give the priest his due. This is the explanation of the concluding clause.
[Accordingly,] whenever the terumah is a substance which the priests do not care about, e.g., terumah from wild figs, carobs, Edomite barley and the like, it is not necessary to separate [a hundredth for the priest]. Instead, since it fell into a 100 times its amount, it is nullified because of its minimal size and the entire mixture is permitted to non-priests.

הלכה ב
נָפְלָה סְאָה תְּרוּמָה לְפָחוֹת מִמֵּאָה נַעֲשֶׂה הַכֹּל מְדֻמָּע וְיִמְכֹּר הַכֹּל לַכֹּהֲנִים בִּדְמֵי תְּרוּמָה חוּץ מִדְּמֵי אוֹתָהּ סְאָה. בַּמֶּה דְּבָרִים אֲמוּרִים כְּשֶׁנִּתְעָרֵב מִין בְּמִינוֹ. אֲבָל מִין בְּשֶׁאֵינוֹ מִינוֹ בְּנוֹתֵן טַעַם אִם יֵשׁ בַּכֹּל טַעַם תְּרוּמָה נַעֲשָׂה הַכֹּל מְדֻמָּע וְיִמָּכֵר לַכֹּהֲנִים חוּץ מִדְּמֵי תְּרוּמָה שֶׁבּוֹ. וְאִם טַעַם הַכֹּל טַעַם חֻלִּין הַכֹּל מֻתָּר לְזָרִים:
כסף משנה
2.
If a se'ah of terumah fell into less than 100 [se'ah of ordinary produce], the entire mixture becomes miduma.4And it is forbidden for a non-priest to partake of it.
In his Commentary to the Mishnah (Demai 1:3), the Rambam explains that Exodus 22:23 uses the term dima as a synonym for terumah. Hence our Sages referred to a mixture of terumah and ordinary produce in this manner.
It should be sold to a priest at the price of terumah5Which is far less than the price of ordinary produce. Since the terumah is not nullified, we have to consider the possibility that every kernel is terumah. with the exception of that se'ah.6Which is given to him without cost.
When does the above apply? When produce becomes mixed with its own kind. If, however, produce becomes mixed with produce of another type, [the ruling is dependent on whether] the flavor [of the terumah] is recognizable or not. If the entire mixture has the flavor of terumah, it is all considered as miduma and should be sold to the priests with the exception of the value of the terumah. If the flavor of the entire mixture is that of the ordinary produce, the entire mixture is permitted to non-priests.7Since the flavor of the terumahis not recognizable, it is considered as nullified. This principle applies with regard to all the Torah's prohibitions [the Rambam's Commentary to the Mishnah (Orlah 2:7)].

הלכה ג
סְאָה תְּרוּמָה שֶׁנָּפְלָה לְמֵאָה וְהִגְבִּיהַּ סְאָה מִן הַכֹּל וְנָפְלָה הַסְּאָה שֶׁהִגְבִּיהַּ לְמָקוֹם אַחֵר אֵינָהּ מְדַמַּעַת אֶלָּא לְפִי חֶשְׁבּוֹן. וְכֵן סְאָה תְּרוּמָה שֶׁנָּפְלָה לְפָחוֹת מִמֵּאָה וְנַעֲשָׂה הַכֹּל מְדֻמָּע וְנָפַל מִן הַמְדֻמָּע לְמָקוֹם אַחֵר אֵינוֹ מְדַמֵּעַ אֶלָּא לְפִי חֶשְׁבּוֹן. כֵּיצַד. הֲרֵי שֶׁנָּפְלוּ עֶשֶׂר סְאִין שֶׁל תְּרוּמָה לְתִשְׁעִים סְאָה חֻלִּין וְנִדְמְעוּ הַכֹּל אִם נָפַל מִמְּדֻמָּע זֶה עֶשֶׂר סְאִין לְפָחוֹת מִמֵּאָה חֻלִּין נִדְמְעוּ שֶׁהֲרֵי יֵשׁ בְּעֶשֶׂר שֶׁל מְדֻמָּע סְאָה שֶׁל תְּרוּמָה. נָפַל לְתוֹכָן פָּחוֹת מֵעֶשֶׂר סְאִין אֵינָן מְדַמְּעוֹת:
כסף משנה
3.
When a se'ah of terumah falls into 100 se'ah and one se'ah was removed from the mixture8As required by Halachah 1., if that se'ah fell into other produce, the question whether the mixture is considered as miduma is determined according to the proportion [of terumah in the first mixture].9Even though the se'ah was taken out to be given to the priest, it is not considered as terumah. Instead, we calculate the proportion of terumah in the first mixture, on that basis, determine how much of the se'ah that fell is considered to be terumah and then see if that amount is one hundredth of the new mixture or not. For example, if one se'ah fell in one hundred se'ah, we consider the se'ah that was removed as slightly less than 1/100th terumah. Thus if it fell into a se'ah or more of ordinary produce, the second mixture is permitted [the Rambam's Commentary to the Mishnah (Terumot 5:5)].Similarly, if a se'ah of terumah fell into less than one hundred se'ah [of ordinary produce] and the entire mixture became miduma and then some of this mixture fell into other [produce], the question whether the mixture is considered as miduma is determined according to the proportion [of terumah in the first mixture].
What is implied? Ten se'ah of terumah fell into 90 se'ah of ordinary produce and the entire mixture became miduma. If ten se'ah from this mixture fell into less than 100 se'ah of ordinary produce, the mixture is considered miduma, because in the ten se'ah of the [original] mixture, there was at least one se'ah of terumah.10And thus a se'ah of terumah is being mixed with less than 100 se'ah of ordinary produce. If less than ten se'ah [of terumah] fell into [the original mixture], the [second] mixture is not considered as miduma [when one se'ah of the first mixture fell into 100 se'ah].

הלכה ד
בַּמֶּה דְּבָרִים אֲמוּרִים בְּדָבָר שֶׁאֵין דַּרְכּוֹ לְהִבָּלֵל כְּגוֹן חִטִּים לְחִטִּים אוֹ קֶמַח לְקֶמַח. אֲבָל דַּרְכּוֹ לְהִבָּלֵל כְּגוֹן שֶׁמֶן תְּרוּמָה לְשֶׁמֶן חֻלִּין אוֹ יֵין תְּרוּמָה לְיֵין חֻלִּין הוֹלְכִין אַחַר הָרֹב. אִם רֹב תְּרוּמָה הֲרֵי זֶה מְדַמֵּעַ כִּתְרוּמָה. וְאִם רֹב חֻלִּין הֲרֵי הוּא כְּחֻלִּין וְאֵינוֹ מְדַמֵּעַ אַף עַל פִּי שֶׁהַכֹּל אֲסוּרִים לְזָרִים:
כסף משנה
4.
When does the above apply? With regard to substances that do not become blended together, e.g., wheat kernels with wheat kernels or flour with flour.11In this instance, every entity remains discrete. It's only that an observer cannot distinguish between the terumah and the ordinary produce (see Radbaz). When, however, substances blend together, e.g., oil that is terumah mixes with ordinary oil or wine that is terumah mixes with ordinary wine, we follow the majority. If the majority is terumah, should the mixture fall into other produce, the ruling is the same as if [the first mixture] was [entirely] terumah.12I.e., instead of calculating the percentage of terumah alone in the new mixture, we consider the first mixture as if it were terumah. Only if the second mixture is 100 times as large as the first is it permitted. If the majority of the [first] mixture is ordinary produce, should that mixture fall into other produce, [the entire first mixture] is considered as ordinary produce and there is never a difficulty concerning a mixture of terumah.13We do not calculate the percentage of terumah in the second mixture. Even if the terumah is more than one hundredth of the second mixture, that mixture is permitted. Nevertheless, in all instances, the entire [first] mixture is forbidden to non-priests.

הלכה ה
סְאָה תְּרוּמָה שֶׁנָּפְלָה לְמֵאָה הִגְבִּיהָהּ וְנָפְלָה אַחֶרֶת הִגְבִּיהָהּ וְנָפְלָה אַחֶרֶת הֲרֵי הַחֻלִּין מֻתָּרִין עַד שֶׁתִּרְבֶּה תְּרוּמָה עֲלֵיהֶן. שֶׁאִם נָפְלוּ לְתוֹךְ הַמֵּאָה חֻלִּין מֵאָה סְאָה וְעוֹד שֶׁל תְּרוּמָה סְאָה אַחַר סְאָה נַעֲשָׂה הַכֹּל מְדֻמָּע:
כסף משנה
5.
When a se'ah of terumah falls into 100 se'ah, [a se'ah of the mixture] was removed, another [se'ah of terumah] fell in, [another se'ah] was removed, and another fell in, the ordinary produce is permitted14Since the mixture was permitted, it is considered as if the se'ah of terumah that fell into it does not exist. We do not consider it as existing within the mixture, so that were it to be combined with other terumah, the entire mixture would be considered miduma. until there is a majority of terumah [in the mixture]. Thus if more than 100 se'ah of terumah fell into 100 se'ah of ordinary produce, se'ah after se'ah [in above manner], the entire mixture is considered as miduma.15The Ra'avad differs with the Rambam concerning this figure, maintaining that the mixture is considered as miduma if 51 se'ah of terumah fall into the ordinary produce in the above manner. His rationale is that since a se'ah is removed from the mixture, it is possible that he is removing a se'ah of ordinary produce. Hence, after 51 se'ah fell and 50 se'ah were removed, it is possible that there is a majority of terumah in the mixture. The Radbaz justifies the Rambam's ruling, explaining that it is logical to assume that each se'ah that is removed has an proportionate amount of terumah and ordinary produce.

הלכה ו
סְאָה תְּרוּמָה שֶׁנָּפְלָה לְמֵאָה וְלֹא הִסְפִּיק לְהַגְבִּיהָהּ עַד שֶׁנָּפְלָה סְאָה אַחֶרֶת. אִם יָדַע בָּרִאשׁוֹנָה קֹדֶם שֶׁתִּפּל הַשְּׁנִיָּה לֹא נִדְמְעוּ. אֶלָּא מַפְרִישׁ סָאתַיִם וְהַשְּׁאָר מֻתָּר הוֹאִיל וְהָיָה לָהּ לַעֲלוֹת הֲרֵי הִיא כְּאִלּוּ עָלְתָה. וְאִם לֹא יָדַע בִּסְאָה רִאשׁוֹנָה אֶלָּא אַחַר שֶׁנָּפְלָה הַשְּׁנִיָּה הֲרֵי זֶה מְדֻמָּע וּכְאִלּוּ נָפְלוּ שְׁתֵּיהֶן כְּאַחַת:
כסף משנה
6.
[The following rules apply when] a se'ah of terumah fell into 100 [se'ah of ordinary produce] and before one se'ah was removed, another se'ah of terumah fell [into the mixture]. If [the owner] was aware of the first se'ah before the second se'ah fell, [the mixture] does not become miduma. Instead, he should remove two se'ah and the remainder is permitted. [The rationale is that] since it should have been taken out,16And thus the entire mixture would be considered as permitted. we consider it as if it was taken out. If, however, he did not become aware of the first se'ah until after the second fell in, the mixture is considered miduma. It is as if both se'ah fell in at the same time.17The Ra'avad comments on the Rambam's ruling, noting that he is following what appears to be the minority opinion in Terumot 5:8. The Kessef Mishneh questions the intent of the Ra'avad's comments and asserts that according to the Tosefta, the majority opinion also accepts the distinction the Rambam makes here. This interpretation is borne out by the Rambam's Commentary to that mishnah.

הלכה ז
אֵין פְּסֹלֶת שֶׁל תְּרוּמָה מִצְטָרֶפֶת עִמָּהּ לֶאֱסֹר הַחֻלִּין. אֲבָל פְּסֹלֶת הַחֻלִּין מִצְטָרֶפֶת עִם הַחֻלִּין לְהַעֲלוֹת הַתְּרוּמָה. כֵּיצַד. סְאָה חִטִּים יָפוֹת שֶׁל תְּרוּמָה שֶׁנָּפְלָה לְמֵאָה סְאָה חִטִּים רָעוֹת שֶׁל חֻלִּין וְטָחַן הַכֹּל. אַף עַל פִּי שֶׁהַמֻּרְסָן שֶׁל חֻלִּין מְרֻבִּין וְשֶׁל תְּרוּמָה מֻעָט וַהֲרֵי קֶמַח שֶׁל תְּרוּמָה בְּפָחוֹת מִמֵּאָה מִקֶּמַח הַחֻלִּין הֲרֵי זֶה עוֹלֶה וּמְשַׁעֲרִין בְּקֶמַח עִם הַמֻּרְסָן שֶׁהוּא מֵאָה וְאֶחָד. אֲבָל אִם נָפְלָה סְאָה חִטִּים רָעוֹת שֶׁל תְּרוּמָה לְפָחוֹת מִמֵּאָה סְאָה חִטִּים יָפוֹת שֶׁל חֻלִּין וְטָחַן הַכֹּל וַהֲרֵי הַקֶּמַח שֶׁל תְּרוּמָה אֶחָד מִמֵּאָה מִקֶּמַח הַחֻלִּין הֲרֵי זֶה עוֹלֶה בְּמֵאָה וְאֶחָד שֶׁהֲרֵי הוֹתִירוּ הַחֻלִּין וּפָחֲתָה הַתְּרוּמָה:
כסף משנה
7.
The waste products of terumah are not combined with it [a mixture of it and ordinary produce] to cause the ordinary produce to be forbidden. The waste products of ordinary produce, by contrast, are combined with it to cause terumah to be nullified in a mixture.
What is implied? A se'ah of high quality wheat that is terumah fell into 100 se'ah of wheat of low quality that is ordinary produce. The owner ground the entire quantity. Even though there is much bran in the ordinary produce and a small amount in the terumah and thus the flour from the terumah is more than one hundredth of the flour from the ordinary produce,18For high quality grain produces more flour and less bran than lower quality grain. Thus more of the lower quality grain is bran and more of the higher quality grain is flour. it is nullified. For we measure the flour with the bran and [together,] it is 101 times [the original amount of terumah]. If, however, a se'ah of low quality wheat that is terumah falls into [slightly] less 100 se'ah of high quality wheat that is ordinary produce and [the owner] ground the entire quantity, [the weight of] the flour that is terumah will be one hundredth of [the weight of] the flour that is ordinary produce. Hence it is nullified because the mixture is 101 times the original amount [of terumah], for the weight of the ordinary produce increased and that of the terumah decreased.19The Ra'avad notes that the Jerusalem Talmud (Terumot 5:9) goes even further and says that the bran in the terumah, since it is considered waste and not food, can be considered as part of the ordinary produce and if there is 100 times the weight of the flour from the terumah when this bran is added to the ordinary produce, the terumah is nullified. The Radbaz and the Kessef Mishneh suggest that the Rambam does not mention this point, because he feels that the Babylonian Talmud - according to which halachah is decided - does not accept it. Nevertheless, it appears that the Shulchan Aruch (Yoreh De'ah 99:1) follows the Ra'avad's view, although the Rama states that as a stringency, the Rambam's perspective should be followed.

הלכה ח
לוֹג יַיִן שֶׁל תְּרוּמָה צָלוּל שֶׁנָּפַל לְמֵאָה לוֹגִין עֲכוּרִין אֵין מוֹצִיאִין שְׁמָרִים שֶׁבָּהֶם. אֶלָּא מַעֲלִין אֶת הַלּוֹג. וְכֵן אִם נָפַל לוֹג עָכוּר לְמֵאָה לוֹגִין צְלוּלִין אֵין מוֹצִיאִין שְׁמָרִים שֶׁבּוֹ:
כסף משנה
8.
When a log20A measure of liquid weight of the Talmudic period. of clear wine that is terumah fell into 100 lugin of cloudy wine21I.e., the dregs had been removed from the wine that is terumah, but had not been removed from the wine which was ordinary produce. that is ordinary produce, we do not remove the dregs from the wine [and only then calculate whether the ordinary wine is 100 times the terumah]. Instead, we nullify the log of terumah.22Counting the dregs of the ordinary produce as part of the mixture. Similarly, if a log of cloudy wine [that is terumah] fell into a 100 log of clear wine, we do not remove the dregs in [the wine that is terumah].23The Rambam is apparently saying that in this instance, the dregs of the terumah wine are counted and unless the ordinary wine is 100 times the amount of that wine including its dregs, it is considered as miduma. See Chapter 11, Halachah 13, which states that the dregs are considered as terumah.
The Ra'avad differs and maintains that in this instance, like the one described in the previous halachah, the dregs of the terumah are not counted, because they are wastes. The Radbaz justifies the Rambam's ruling, explaining that wine dregs are different than the wastes mentioned in the previous halachah, because they have the flavor of wine and can produce wine.

הלכה ט
לוֹג מַיִם שֶׁנָּפַל לְתִשְׁעִים וְתִשְׁעָה לוֹגִין יַיִן וְאַחַר כָּךְ נָפַל לְתוֹךְ הַכֹּל לוֹג יַיִן שֶׁל תְּרוּמָה נִדְמַע הַכֹּל. שֶׁאֵין הַמַּיִם מַעֲלֶה אֶת הַיַּיִן:
כסף משנה
9.
When a log of water fell into 99 lugim of wine and then a log of wine that is terumah fell into the mixture, the entire mixture is considered as miduma, because water does not nullify [the existence of] wine.24The Ra'avad explains the rationale for this ruling as follows: The water is not considered as the same type as wine. Hence, it cannot nullify it unless the flavor of the wine is no longer noticeable. The wine, by contrast, is considered its type and it requires 100 times the weight of the terumah. The Kessef Mishneh explains that this can be understood as the Rambam's intent.

הלכה י
סְאָה תְּרוּמָה שֶׁנָּפְלָה לְפָחוֹת מִמֵּאָה חֻלִּין וְנָפְלוּ חֻלִּין אֲחֵרִים עַד שֶׁהוֹסִיפוּ עַל מֵאָה. אִם בְּשׁוֹגֵג הֲרֵי זוֹ עוֹלָה בְּמֵאָה וְאֶחָד. וְאִם בְּמֵזִיד הֲרֵי הַכֹּל מְדֻמָּע שֶׁאֵין מְבַטְּלִין אִסּוּרֵי תּוֹרָה לְכַתְּחִלָּה:
כסף משנה
10.
[The following rules apply when] a se'ah of terumah fell into less than 100 se'ah of ordinary produce and then other ordinary produce fell into the mixture so that there was more than 100 times [the weight of the terumah]. If [the second batch of produce was added] unknowingly, [the terumah] is nullified because there is 101 [times the original weight]. If he mixed it intentionally, the entire mixture is considered as miduma, because we do not nullify the existence of substances prohibited by Scriptural Law as an initial preference.25The Radbaz notes that in Hilchot Ma'achalot Assurot 15:25, the Rambam writes: It is forbidden to nullify a substance forbidden by Scriptural Law as an initial and preferred measure. If, however, one nullified it, the mixture is permitted. Nevertheless, our Sages penalized such a person and forbade the entire mixture. It appears to me that since this is a penalty, we forbid this mixture only to the person who transgressed and nullified the prohibited substance. For others, however, the entire mixture is permitted. In the present instance, however, it appears that the produce is considered as miduma, not only for the person who mixed together, but for everyone. The Radbaz differentiates between the two situations, explaining that in Hilchot Ma'achalot Assurot, the Rambam is speaking about a forbidden substance. Hence, if it was considered forbidden, it would have no value entirely. In our halachah, even if the mixture is considered miduma, it can be sold to priests and thus, it will not be wasted entirely.

הלכה יא
תְּרוּמַת חוּצָה לָאָרֶץ מֻתָּר לְבַטְּלָהּ בְּרֹב וְאוֹכְלָהּ בִּימֵי טֻמְאָתוֹ וְלֹא עוֹד אֶלָּא אִם הָיָה לוֹ יַיִן שֶׁל תְּרוּמַת חוּצָה לָאָרֶץ נוֹטֵל מִמֶּנּוּ לוֹג אֶחָד וְנוֹתֵן עָלָיו שְׁנֵי לוֹגִין חֻלִּין וְנִמְצָא הַכֹּל שְׁלֹשָׁה וְאַחַר כָּךְ נוֹטֵל מִיַּיִן שֶׁל תְּרוּמָה לוֹג וְנוֹתֵן לְתוֹךְ הַשְּׁלֹשָׁה וּמַגְבִּיהַּ מֵאַרְבַּעְתָּן לוֹג וְשׁוֹתֶה. וְחוֹזֵר וּמַשְׁלִיךְ לְתוֹכָן לוֹג אַחֵר וְחוֹזֵר וְנוֹטֵל לוֹג וְשׁוֹתֶה. וְכֵן נוֹתֵן לוֹג תְּרוּמָה וְנוֹטֵל לוֹג מִן הַתַּעֲרֹבֶת עַד שֶׁיִּכְלֶה כָּל הַיַּיִן שֶׁל תְּרוּמָה. וְנִמְצָא שֶׁנָּטַל כַּמָּה לוֹגִין בִּשְׁנֵי לוֹגִין שֶׁל חֻלִּין:
כסף משנה
11.
It is, however, permitted to nullify terumah from the Diaspora [by mixing it] with a majority of permitted substances26I.e., since the prohibition is of Rabbinic origin, one may nullify it as an initial preference, as stated in Hilchot Ma'achalot Assurot 15:26. and eat it during the time when one is ritually impure.27The Radbaz explains that the mixture may be eaten by a priest even when he is ritually impure or by a non-priest. Not only that, if a person possesses wine that is terumah from the Diaspora, he should take one log of this wine and mix it with two lugim of ordinary [wine]. Thus there are three lugim.28And the wine that is terumah is nullified, because it is mixed with a majority of ordinary produce. Afterwards, he can add another log of the terumah wine into the three lugim and then take one log from the four and drink it.29The Ra'avad differs, maintaining that once there is no longer a majority of ordinary produce, the mixture is forbidden. The Kessef Mishneh justifies the Rambam's ruling, explaining that once the terumah is nullified, it does not become a factor again if other terumah is added. He may then add another log [of terumah wine] and take out a log and drink it. Similarly, he may continue adding a log of terumah and removing a log until all the wine that is terumah is completed. Thus he can nullify several lugim [of terumah] in two lugim of ordinary produce.

הלכה יב
הַזּוֹרֵעַ תְּרוּמָה בְּצַד הַחֻלִּין וְלֹא נוֹדַע אֵי זֶהוּ זֶרַע תְּרוּמָה אֲפִלּוּ הָיָה מֵאָה לְגִנָּה שֶׁל תְּרוּמָה וּלְגִנָּה אַחַת שֶׁל חֻלִּין כֻּלָּן מֻתָּרִין. בַּמֶּה דְּבָרִים אֲמוּרִים בְּדָבָר שֶׁזַּרְעוֹ כָּלֶה בַּקַּרְקַע כְּגוֹן הַחִטִּים וְהַשְּׂעוֹרִים וְכַיּוֹצֵא בָּהֶן. אֲבָל דָּבָר שֶׁאֵין זַרְעוֹ נִפְסָד בָּאָרֶץ כְּגוֹן הַשּׁוּם וְהַבְּצָלִים אֲפִלּוּ מֵאָה לְגִנָּה שֶׁל חֻלִּין וּלְגִנָּה אַחַת שֶׁל תְּרוּמָה תַּעֲרֹבֶת בֵּינֵיהֶן הֲרֵי הַכֹּל מְדֻמָּע. וְאִם נִתְלַשׁ הַכֹּל תַּעֲלֶה הַתְּרוּמָה בְּאֶחָד וּמֵאָה וְלֹא יִתְלֹשׁ לְכַתְּחִלָּה:
כסף משנה
12.
When one sows terumah next to ordinary produce and cannot identify which produce is terumah and which is ordinary produce, the entire batch is permitted even if there were 100 rows of terumah and [only] one row of ordinary produce.30The rationale is that the produce that grows from terumah is not terumah and is forbidden to non-priests only as a stringency (Chapter 11, Halachot 21-22). Hence, if there is any confusion about which produce is terumah, it is all permitted.
When does the above apply? With regard to produce whose seed decomposes in the earth, e.g., wheat, barley, and the like.31For then there is no trace of the original plant. If, however, the seeds do not decompose, e.g., garlic and onions,32In which instance, the new plant grows from a bulb of the original one and that original plant never decomposes entirely. even if 100 rows are ordinary produce and one row is terumah, the entire mixture is miduma. 33For the terumah is distinct and has not become mixed with the ordinary produce [the Rambam's Commentary to the Mishnah (Terumot 9:5)]. If the entire crop is harvested,34Without paying attention to the prohibition. terumah can be nullified in a mixture of 100 times its weight, but, as an initial and preferred option, one should not harvest the crop.35For as stated above, as an initial preference, a prohibited substance should not be nullified. It must, however, be emphasized, the Rambam's intent is not to let the produce remain in the ground forever. Instead, it should be harvested as produce which is miduma and sold to priests at the price of terumah.

הלכה יג
שְׁתֵּי קֻפּוֹת אַחַת שֶׁל תְּרוּמָה וְאַחַת שֶׁל חֻלִּין וְאֵין יָדוּעַ אֵי זוֹ הִיא. אוֹ שֶׁנָּפְלָה סְאָה שֶׁל תְּרוּמָה לְתוֹךְ אַחַת מֵהֶן וְאֵין יָדוּעַ לְהֵיכָן נָפְלָה וְאַחַר כָּךְ נָפְלָה אַחַת מִשְּׁתֵּי קֻפּוֹת לְתוֹךְ הַחֻלִּין אֵינָן מְדַמַּעְתָּן. וְכֵן אִם זָרַע אַחַת מֵהֶם הַגִּדּוּלִין חֻלִּין לְכָל דָּבָר. וְהַשְּׁנִיָּה נוֹהֵג בָּהּ כִּתְרוּמָה. נָפְלָה הַקֻּפָּה הַשְּׁנִיָּה לְמָקוֹם אַחֵר אֵינָהּ מְדַמַּעַת. וְכֵן אִם זָרַע אַחֵר אֶת הַשְּׁנִיָּה הַגִּדּוּלִין חֻלִּין. נָפְלוּ שְׁתֵּיהֶן לְמָקוֹם אֶחָד מְדַמַּעַת כַּקְּטַנָּה שֶׁבִּשְׁתֵּיהֶן. זָרַע אֶחָד אֶת שְׁתֵּיהֶם בְּדָבָר שֶׁזַּרְעוֹ כָּלֶה הַגִּדּוּלִין חֻלִּין. וּבְדָבָר שֶׁאֵין זַרְעוֹ כָּלֶה הַגִּדּוּלִין מְדֻמָּע. בַּמֶּה דְּבָרִים אֲמוּרִים בְּזוֹרֵעַ אֶת הַשְּׁנִיָּה עַד שֶׁלֹּא קָצַר אֶת הָרִאשׁוֹנָה. אֲבָל קָצַר אֶת הָרִאשׁוֹנָה וְאַחַר כָּךְ זָרַע אֶת הַשְּׁנִיָּה אֲפִלּוּ בְּדָבָר שֶׁאֵין זַרְעוֹ כָּלֶה הַגִּדּוּלִין חֻלִּין שֶׁאֵין תָּלוּשׁ וּמְחֻבָּרִין נַעֲשִׂין חוֹבָה זֶה לָזֶה:
כסף משנה
13.
When there are two containers of produce, one containing terumah and one containing ordinary produce and it is not known [which contains the ordinary produce and which contains the terumah], if [the contents of] one of these containers falls into ordinary produce, [the mixture] is not considered as miduma.36Since we are unsure of the identity of the produce that fell into the mixture, we do not rule it forbidden because of the doubt. Instead, we say that the ordinary produce fell into it.
This halachah involves produce that is forbidden as terumah according to Rabbinic decree, e.g., terumah from the Diaspora or a mixture of terumahand a majority of ordinary produce. These principles are also applied in other contexts, see Chapter 10, Halachah 14, and Shulchan Aruch (Yoreh De'ah 111:1).
[This same law applies if produce that is] terumah fell into one of two containers [of ordinary produce], but one does not know which one and afterwards, one of those containers fell into ordinary produce.
Similarly, if one sowed [the grain from] one of the two containers, the produce that grows is considered as ordinary produce with regard to all matters.37Even if the original was terumah [The produce in] the remaining container is considered as terumah.38Because of the doubt applying to its status. If [the contents of] the second container fell into other produce, [the mixture] is not considered as miduma.39The same principle applies here. Since we are unsure if the identity of the produce which fell into the mixture, we do not rule that it is forbidden because of the doubt. Similarly, if another person sowed [the contents of] the second container, the produce that grows is considered as ordinary produce.40Since each person asks concerning the status of the produce that he sowed individually, both are permitted, because in each instance, there is a doubt.
If [the contents of] both containers fall into one mixture of other produce, the mixture is considered miduma according to the amount of produce in the smaller container.41I.e., if the larger container contained one se'ah and the smaller container contained half a se'ah, we require the mixture to contain 50 ½ se'ah to be permitted, not 101 se'ah. If one person sowed both of them,42And thus the same person is asking about both plantings of produce. Hence, there is more room for stringency. if the produce is a species where the seed decomposes, the produce that grows is considered as ordinary produce.43Since no trace of the original produce remains, we rule leniently.If the seed does not decompose, the produce that grows is miduma.44Since the produce concerning which a doubt arose originally continues to exist, stringency is called for.
When does the above apply? When one sowed [the contents of] the second container before the first batch of produce was harvested.45For then it is considered as if he sowed them both together. If, however, he harvested the first batch of produce before sowing the second, the produce that grows is considered as ordinary produce even when the seed does not decompose. [The rationale is that] produce that has been reaped and produce that is growing are not considered as indicators of each other's status.

הלכה יד
שְׁתֵּי קֻפּוֹת אַחַת שֶׁל חֻלִּין וְאַחַת שֶׁל תְּרוּמָה וְלִפְנֵיהֶן שְׁתֵּי סְאִין אַחַת שֶׁל חֻלִּין וְאַחַת שֶׁל תְּרוּמָה וְנָפְלוּ אֵלּוּ לְתוֹךְ אֵלּוּ מֻתָּרִין. שֶׁאֲנִי אוֹמֵר חֻלִּין לְתוֹךְ חֻלִּין נָפְלוּ וּתְרוּמָה לְתוֹךְ הַתְּרוּמָה וְאַף עַל פִּי שֶׁלֹּא רַבּוּ חֻלִּין עַל הַתְּרוּמָה. בַּמֶּה דְּבָרִים אֲמוּרִים בִּתְרוּמָה בַּזְּמַן הַזֶּה שֶׁהוּא מִדִּבְרֵיהֶם. אֲבָל בִּתְרוּמָה שֶׁל תּוֹרָה עַד שֶׁיִּרְבּוּ חֻלִּין עַל הַתְּרוּמָה:
כסף משנה
14.
When there are two containers [of produce], one containing ordinary produce and the other, containing terumah and two se'ah, one of ordinary produce and one of terumah, and both se'ah fall into these containers, [one into each], the produce is permitted. We assume that the ordinary produce fell into [the container of] ordinary produce and that the terumah fell into [the container of] terumah. [This applies] even though the weight of the ordinary produce is not greater than that of the terumah.46But rather they are of the same weight. Were there to be a majority of ordinary produce, according to Scriptural Law, the existence of the terumah would already be nullified and thus there would be greater room for leniency. Nevertheless, as the Rambam continues to explain, even when there is not a majority, since the entire question is one of Rabbinic Law, we allow leniency. If, however, there is a majority of terumah, even when it is forbidden only according to Rabbinic Law, the mixture is forbidden.
When does the above apply? With regard to terumah in the present era, for the requirement is of Rabbinic origin.47See Chapter 1, Halachah 26. If the terumah is mandated by Scriptural Law, [the above ruling does not apply unless] the weight of the ordinary produce is greater than that of the terumah.48In such an instance, the existence of the terumah would already be nullified and thus there would be greater room for leniency, since then the question is one of Rabbinic Law. The above leniency applies only with regard to such questions and not to questions involving Scriptural Law.

הלכה טו
סְאָה תְּרוּמָה שֶׁנָּפְלָה לְתוֹךְ הַכְּרִי וְאָמַר תְּרוּמַת הַכְּרִי זֶה לְתוֹכוֹ בְּמָקוֹם שֶׁנָּפְלָה אוֹתָהּ סְאָה שָׁם נִסְתַיְּמָה תְּרוּמַת הַכְּרִי וְנִדְמַע הַכֹּל בִּתְרוּמָה שֶׁנָּפְלָה וּבִתְרוּמַת הַכְּרִי. אָמַר תְּרוּמַת הַכְּרִי בִּצְפוֹנוֹ חוֹלְקִין אוֹתוֹ לִשְׁנַיִם וְהַחֵצִי שֶׁבַּצָּפוֹן לִשְׁנַיִם וְנִמְצָא רְבִיעַ הַכְּרִי שֶׁהוּא צְפוֹן צְפוֹנִי הוּא הַמְדֻמָּע:
כסף משנה
15.
When a se'ah of terumah falls into a grainheap49From which terumah and the tithes have not been separated. and [the owner] states: "The terumah of this grainheap is in its midst," the borders of the terumah are defined where the se'ah fell and the entire mixture becomes miduma because of the terumah which fell in and the terumah of the grainheap.50Though in and of itself, the amount of terumah which fell in the grainheap would not disqualify it, when it is combined with the terumah that was designated it does.
The Ra'avad appears to have had a different version of the Jerusalem Talmud, Terumot 3:3, the Rambam's source. Hence he differs with the Rambam's ruling..

If he said: "The terumah of the grainheap is in its northern portion,"51This law applies even if no terumah has fallen into the grainheap. we divide the grainheap in half, and then the northern half in half. Thus the northern most quarter of the grainheap is miduma.52Because there is less than one hundred times the weight of the terumah in that corner.

הלכה טז
הָיוּ לְפָנָיו שְׁנֵי כְּרָיִים וְאָמַר תְּרוּמַת שְׁנֵי כְּרָיִים בְּאֶחָד מֵהֶן הֲרֵי שְׁנֵיהֶן מְדֻמָּעִין. הָיוּ לְפָנָיו שְׁתֵּי סְאִין וּכְרִי אֶחָד וְאָמַר הֲרֵי אַחַת מִן הַסְּאִין הָאֵלּוּ עֲשׂוּיָה תְּרוּמָה עַל הַכְּרִי הַזֶּה הֲרֵי אַחַת מֵהֶן תְּרוּמָה וְאֵין יָדוּעַ אֵי זוֹ הִיא. הָיוּ לְפָנָיו שְׁנֵי כְּרָיִים וּסְאָה אַחַת וְאָמַר הֲרֵי זוֹ תְּרוּמָה עַל אֶחָד מִן הַכְּרָיִים הַלָּלוּ הֲרֵי הוּא תְּרוּמָה וְנִתְקַן אֶחָד מֵהֶן וְאֵין יָדוּעַ אֵי זֶה הוּא הַמְתֻקָּן מִן הַטֶּבֶל:
כסף משנה
16.
If there were two grainheaps before a person and he said: 'The terumah for both grainheaps is in one of them," they are both considered miduma.53The one which contains the terumah is certainly miduma. Since we do not know which one that is, they are both considered as miduma.
If there were two se'ah of grain and one grainheap before a person and he said: "One of these se'ah is considered terumah for this grainheap," one of them is terumah and he does not know which.54Hence he must observe the restrictions of terumah with regard to both of them. If there were two grainheaps and one se'ah before him and he said: "This is terumah for one of the grainheaps," [the se'ah] is terumah and [terumah has been separated from] one of the grainheaps, but he does not know which one is no longer tevel.55Hence terumah must be separated in a conditional manner. One must bring other produce and say: "If terumah has not been separated for this grainheap, than this is terumah for it. But if it is the other grainheap from which terumah has not been separated, it is terumah for that."

זרעים הלכות תרומות פרק יג
Zeraim Terumos Chapter 13