Halacha

הלכה א
אֶחָד הַשּׂוֹכֵר מֵחֲבֵרוֹ שָׂדֶה לְזָרְעָהּ אוֹ כֶּרֶם לֶאֱכל פֵּרוֹתָיו בְּדָמִים אוֹ שֶׁשָּׂכַר מִמֶּנּוּ בְּפֵרוֹת קְצוּבִים כְּגוֹן שֶׁשָּׂכַר מִמֶּנּוּ שָׂדֶה זוֹ בְּעֶשְׂרִים כּוֹר בְּשָׁנָה וְכֶרֶם זֶה בְּעֶשְׂרִים כַּדֵּי יַיִן בְּכָל שָׁנָה שְׁנֵיהֶן דִּין אֶחָד יֵשׁ לָהֶן. וְהַשּׂוֹכֵר בְּפֵרוֹת הוּא הַנִּקְרָא חוֹכֵר:
כסף משנה
1.
The same laws apply when a person rents a field from a colleague to sow, or a vineyard to benefit from its fruits and agrees to pay him money or agrees to pay him a fixed amount of produce - e.g., he rented a particular field for 20 kor of grain a year or a particular vineyard for 20 jugs of wine a year. A person who rents property and agrees to pay in produce is called a chocher.

הלכה ב
הַמְקַבֵּל שָׂדֶה אוֹ פַּרְדֵּס כְּדֵי לַעֲבֹד אוֹתוֹ וּלְהוֹצִיא עָלָיו יְצִיאוֹת וְיִתֵּן לְבַעַל הַקַּרְקַע שְׁלִישׁ הַתְּבוּאוֹת אוֹ רְבִיעַ אוֹ מַה שֶּׁיַּתְנוּ בֵּינֵיהֶן וְהוּא הַנִּקְרָא מְקַבֵּל. כָּל דָּבָר שֶׁהוּא לִסְיַג הָאָרֶץ בַּעַל הַקַּרְקַע חַיָּב בּוֹ וְכָל דָּבָר שֶׁהוּא שְׁמִירָה יְתֵרָה הַחוֹכֵר אוֹ הַמְקַבֵּל חַיָּב בּוֹ. הַקַּרְדֹּם שֶׁחוֹפְרִין בּוֹ הָאָרֶץ וְהַכֵּלִים שֶׁנּוֹשְׂאִין בָּהֶן הֶעָפָר וְהַדְּלִי וְהַכַּד וְכַיּוֹצֵא בָּהֶן שֶׁדּוֹלִין בָּהֶן הַמַּיִם עַל בַּעַל הַקַּרְקַע. וַחֲטִיטַת הַמְּקוֹמוֹת שֶׁמְּקַבְּצִין בָּהֶן הַמַּיִם עַל הַחוֹכֵר אוֹ עַל הַמְקַבֵּל:
כסף משנה
2.
When a person takes a field or an orchard with the intent of working it, investing in it and giving the owner a third, a fourth or whatever other percentage of the harvest that they agree to, he is called a mekabel.
The following rules apply with regard to all the types of contracts mentioned above. Whenever an improvement is necessary for the sake of the land itself, it is the responsibility of the owner of the land to provide it. Whenever an improvement is an added measure of security, the renter is responsible for it.
The ax that is used to break up the land, the containers used to carry away earth, the bucket, the jug or the like that is used to draw water are the responsibility of the owner of the land. Digging the irrigation ditches, by contrast, is the responsibility of the renter.

הלכה ג
הַשּׂוֹכֵר אוֹ הַמְקַבֵּל שָׂדֶה מֵחֲבֵרוֹ לְשָׁנִים מוּעָטוֹת לֹא יִזְרָעֶנָּה פִּשְׁתָּן. שְׂכָרָהּ אוֹ קִבְּלָהּ שֶׁבַע שָׁנִים זוֹרְעָהּ שָׁנָה רִאשׁוֹנָה פִּשְׁתָּן וְאֵין הַשְּׁבִיעִית מִן הַמִּנְיָן. שְׂכָרָהּ אוֹ קִבְּלָהּ שָׁבוּעַ אֶחָד שְׁבִיעִית מִן הַמִּנְיָן:
כסף משנה
3.
When a person rents or makes a sharecropping agreement with regard to a colleague's field for only a few years, he should not sow flax. If he rents it or enters a sharecropping agreement for seven years, he may sow flax for the first year. The Sabbatical year is not included in this reckoning. If he rents it or enters a sharecropping agreement for a seven-year period, the Sabbatical year is included in this reckoning.

הלכה ד
הַחוֹכֵר אוֹ הַמְקַבֵּל שָׂדֶה מֵחֲבֵרוֹ וְהִיא בֵּית הַשְּׁלָחִין אוֹ בֵּית הָאִילָן וְיָבְשָׁה מַעְיַן בֵּית הַשְּׁלָחִין וְלֹא פָּסַק הַנָּהָר הַגָּדוֹל אֶלָּא אֶפְשָׁר לְהָבִיא מִמֶּנּוּ בִּדְלִי. אוֹ שֶׁנִּקְצַץ הָאִילָן שֶׁל בֵּית הָאִילָנוֹת אֵינוֹ מְנַכֶּה לוֹ מֵחַכִּירוֹ. וְאִם מַכַּת מְדִינָה הִיא כְּגוֹן שֶׁיָּבַשׁ הַנָּהָר מְנַכֶּה לוֹ מֵחַכִּירוֹ. הָיָה עוֹמֵד בְּתוֹךְ הַשָּׂדֶה וְאָמַר לוֹ בֵּית הַשְּׁלָחִין הַזֶּה אֲנִי מַשְׂכִּיר לְךָ בֵּית הָאִילָן זֶה אֲנִי מַשְׂכִּיר יָבֵשׁ הַמַּעְיָן אוֹ נִקְצַץ הָאִילָן מְנַכֶּה מֵחַכִּירוֹ שֶׁהֲרֵי הוּא עוֹמֵד בְּתוֹכָהּ וְלֹא אָמַר לוֹ הַזֶּה אֶלָּא כְּמִי שֶּׁאוֹמֵר כְּמוֹת שֶׁהִיא עַתָּה אֲנִי מַשְׂכִּיר לְפִיכָךְ אִם לֹא הָיָה עוֹמֵד בְּתוֹכָהּ וְאָמַר לוֹ בֵּית הַשְּׁלָחִין אֲנִי מַשְׂכִּיר לְךָ אוֹ בֵּית הָאִילָן וְיָבֵשׁ הַמַּעְיָן אוֹ שֶׁנִּקְצַץ הָאִילָן אֵינוֹ מְנַכֶּה לוֹ מֵחַכִּירוֹ:
כסף משנה
4.
The following laws apply when a person rents or makes a sharecropping agreement with regard to a colleague's field that is parched and requires irrigation, and the spring used to irrigate the field dries up, but the larger river has not ceased to flow, and it is possible to carry water from it in a bucket. The renter may not reduce his payments. If this is a problem that affects the entire region - e.g., the river itself dried up - he may reduce his payments. Similar laws apply if one rents an orchard and the trees of the orchard are cut down.
Different rules apply when the owner was standing in his field and told the renter: "I am renting you this parched field," or "I am renting you this orchard." If the spring dries up or the tree is chopped down, he may reduce his payments. Since he was standing in the property when he made that statement, we assume that by saying: "this field" or "this orchard," his intent was: "I am renting it to you in its present condition."
Therefore, when the owner is not standing in his field and told the renter: "I am renting you this parched field," or "I am renting you this orchard." If the spring dries up or the tree is chopped down, he may not reduce his payments.

הלכה ה
הַשּׂוֹכֵר אוֹ הַמְקַבֵּל שָׂדֶה מֵחֲבֵרוֹ וַאֲכָלָהּ חָגָב אוֹ נִשְׁתַּדְּפָה אִם אֵרַע דָּבָר זֶה לְרֹב הַשָּׂדוֹת שֶׁל אוֹתָהּ הָעִיר מְנַכֶּה לוֹ מֵחַכִּירוֹ הַכּל לְפִי הַהֶפְסֵד שֶׁאֵרְעוֹ וְאִם לֹא פָּשְׁטָה הַמַּכָּה בְּרֹב הַשָּׂדוֹת אֵינוֹ מְנַכֶּה לוֹ מֵחַכִּירוֹ אַף עַל פִּי שֶׁנִּשְׁתַּדְּפוּ כָּל הַשָּׂדוֹת שֶׁל בַּעַל הַקַּרְקַע. נִשְׁתַּדְּפוּ כָּל הַשָּׂדוֹת שֶׁל הַשּׂוֹכֵר אוֹ הַמְקַבֵּל אַף עַל פִּי שֶׁפָּשְׁטָה הַמַּכָּה בְּרֹב הַשָּׂדוֹת אֵינוֹ מְנַכֶּה לוֹ מֵחַכִּירוֹ שֶׁאֵין זֶה הַהֶפְסֵד תָּלוּי אֶלָּא בַּשּׂוֹכֵר שֶׁהֲרֵי כָּל שְׂדוֹתָיו נִשְׁתַּדְּפוּ. הִתְנָה עָלָיו בַּעַל הַקַּרְקַע שֶׁיִּזְרָעֶנָּה חִטִּים וּזְרָעָהּ שְׂעוֹרִים אוֹ שֶׁלֹּא זְרָעָהּ כְּלָל אוֹ שֶׁזְּרָעָהּ וְלֹא צָמְחָה אַף עַל פִּי שֶׁבָּא חָגָב אוֹ שִׁדָּפוֹן וְהֻכְּתָה רֹב הַמְּדִינָה אֵינוֹ מְנַכֶּה לוֹ מֵחַכִּירוֹ. וְעַד מָתַי חַיָּב לְהִטַּפֵּל וְלִזְרֹעַ פַּעַם אַחֶרֶת אִם לֹא צָמְחָה כָּל זְמַן שֶׁרָאוּי לִזְרִיעָה בְּאוֹתוֹ מָקוֹם:
כסף משנה
5.
The following rules apply when a person rents or makes a sharecropping agreement with regard to a colleague's field, and the crops are eaten by locusts or destroyed by drought. If this condition prevailed among the majority of the fields of that city, he may reduce his payments according to the extent of the loss that he suffered. If this blight did not prevail among the majority of the fields, he may not reduce his payments. This law applies even though all the fields belonging to this land owner were ravaged.
If all the fields of the renter or the sharecropper were ravaged, even though the blight also affected most of the other fields, he may not reduce his payment. For the loss is dependent on the renter's bad fortune, as evidenced by the fact that all his fields were ravaged.
If the owner stipulated that the renter should sow the field with wheat, and he sowed it with barley, did not sow it at all or sowed it and nothing grew, the renter may not reduce his payments even though locusts or a drought came and the majority of the fields were ravaged. Until when must he till it and sow it a second time if the first crop does not grow? Until the time when it is fit to sow in that place.

הלכה ו
הַשּׂוֹכֵר אוֹ הַמְקַבֵּל שָׂדֶה מֵחֲבֵרוֹ מָקוֹם שֶׁנָּהֲגוּ לִקְצֹר יִקְצֹר וְאֵינוֹ רַשַּׁאי לַעֲקֹר. לַעֲקֹר יַעֲקֹר וְאֵינוֹ רַשַּׁאי לִקְצֹר. וּשְׁנֵיהֶם מְעַכְּבִין זֶה עַל זֶה. וּמָקוֹם שֶׁנָּהֲגוּ לַחְרשׁ אַחֲרָיו יַחְרשׁ. מָקוֹם שֶׁנָּהֲגוּ לְהַשְׂכִּיר אִילָנוֹת עַל גַּב קַרְקַע מַשְׂכִּירִין וְאַף עַל פִּי שֶׁהִשְׂכִּיר לוֹ סְתָם בְּפָחוֹת מִן הַיָּדוּעַ. וּמָקוֹם שֶׁנָּהֲגוּ שֶׁלֹּא לְהַשְׂכִּיר אִילָנוֹת אֵין לוֹ אִילָנוֹת אַף עַל פִּי שֶׁשָּׂכַר מִמֶּנּוּ בְּיֶתֶר עַל הַיָּדוּעַ. הַכּל כְּמִנְהַג הַמְּדִינָה:
כסף משנה
6.
The following rules apply when a person rents or makes a sharecropping agreement with regard to a colleague's field. If it is customary in that locale to cut down the crops, the renter should cut them down. He is not permitted to uproot them. If it is customary to uproot the crops, the renter should uproot them. He is not permitted to cut them down. Either of them can prevent the custom from being changed.
In a locale where it is customary to plow after the harvesting, the renter should plow. In a locale where it is customary to rent trees together with land, they are considered to have been rented out. This applies even though the owner rented the property for a price that is lower than usual. In a locale where it is not customary to rent trees together with land, they are not considered to have been rented out. This applies even though the owner rented the property for a price that is higher than usual. Everything follows the local custom.

הלכה ז
הַחוֹכֵר שָׂדֶה מֵחֲבֵרוֹ בַּעֲשָׂרָה כּוֹר חִטִּים וְלָקְתָה נוֹתֵן לוֹ מִתּוֹכָהּ. הָיוּ חִטֶּיהָ יָפוֹת לֹא יֹאמַר לוֹ הֲרֵינִי לוֹקֵחַ לְךָ מִן הַשּׁוּק אֶלָּא נוֹתֵן לוֹ מִתּוֹכָהּ. חָכַר מִמֶּנּוּ כֶּרֶם בַּעֲשָׂרָה סַלֵּי עֲנָבִים וְהִקְרִיסוּ אַחַר שֶׁנִּבְצְרוּ וְכֵן עֳמָרִים שֶׁלָקוּ אַחַר שֶׁנִּקְצְרוּ נוֹתֵן לוֹ מִתּוֹכָן. חֲכָרוֹ בַּעֲשָׂרָה כַּדֵּי יַיִן וְהֶחְמִיץ חַיָּב לִתֵּן לוֹ יַיִן טוֹב. חֲכָרָהּ מִמֶּנּוּ בְּמֵאָה עֳמָרִים שֶׁל אַסְפַּסְתָּא וּזְרָעָהּ מִין אַחֵר וְאַחַר כָּךְ חֲרָשָׁהּ וּזְרָעָהּ אַסְפַּסְתָּא וְלָקְתָה אוֹ שֶׁזְּרָעָהּ בַּתְּחִלָּה אַסְפַּסְתָּא וַחֲרָשָׁהּ וְאַחַר כָּךְ זְרָעָהּ פַּעַם אַחֶרֶת וְלָקְתָה אֵינוֹ נוֹתֵן לוֹ מִתּוֹכָהּ אֶלָּא נוֹתֵן לוֹ אַסְפַּסְתָּא טוֹבָה שֶׁהֲרֵי שִׁנָּה. וְכֵן כָּל כַּיּוֹצֵא בָּזֶה:
כסף משנה
7.
When a person rents a field from a colleague for ten kor of wheat and it suffered blight, he may pay the owner from the wheat of that field. Conversely, if it produces extremely high quality wheat, he should not tell the owner: "I will purchase wheat for you from the marketplace." Instead, he must give him the wheat from the field.
If a person rents a vineyard for ten baskets of grapes and they become sour after they were harvested, the renter may give the owner the grapes from the vineyard. A similar ruling applies to sheaves of grain that became ruined after they were harvested. If, however, a person rents a vineyard for ten jugs of wine, and the wine becomes sour, he is obligated to provide the owner with good wine.
The following rules apply when a person rented a field for 100 sheaves of cattle fodder, sowed another crop and then plowed the field and sowed it with cattle fodder. If it suffered blight, the renter may not give the owner the cattle fodder growing in it. Instead, he must give him high quality fodder, for he deviated from the terms of the initial agreement. Similar rules apply even if he sowed it with fodder at the outset, plowed it and then sowed it again and it suffered blight or in any other situation where the damage to the crops comes after the renter deviates from the initial agreement.

הלכה ח
הַחוֹכֵר שָׂדֶה מֵחֲבֵרוֹ וְלֹא רָצָה לְנַכֵּשׁ וְאָמַר לוֹ מַה הֶפְסֵד יֵשׁ לְךָ הֲרֵינִי נוֹתֵן לְךָ חַכִּירְךָ אֵין שׁוֹמְעִין לוֹ שֶׁהֲרֵי הוּא אוֹמֵר לוֹ לְמָחָר אַתָּה יוֹצֵא מִמֶּנָּה וְהִיא מַעֲלָה עֲשָׂבִים. וַאֲפִלּוּ אָמַר לוֹ בָּאַחֲרוֹנָה אֲנִי חוֹרֵשׁ אוֹתָהּ אֵין שׁוֹמְעִין לוֹ:
כסף משנה
8.
The following rules apply when a person rents a field from a colleague, but does not desire to weed it. Although the renter tells the owner: "What will you suffer? I will give you the amount stipulated regardless," his words are not heeded. For the owner may respond: "Ultimately, you will leave it, and it will grow weeds for me."
Even if the renter says: "At the end I will plow it," his words are not heeded.

הלכה ט
הַחוֹכֵר שָׂדֶה מֵחֲבֵרוֹ לְזָרְעָהּ שְׂעוֹרִים לֹא יִזְרָעֶנָּה חִטִּים מִפְּנֵי שֶׁהַחִטִּין מַכְחִישׁוֹת אֶת הַקַּרְקַע יֶתֶר מֵהַשְּׂעוֹרִים. שְׂכָרָהּ לְזָרְעָהּ חִטִּים יִזְרָעֶנָּה שְׂעוֹרִים. קִטְנִית לֹא יִזְרָעֶנָּה תְּבוּאָה. תְּבוּאָה יִזְרָעֶנָּה קִטְנִית. וּבְבָבֶל וְכַיּוֹצֵא בָּהּ לֹא יִזְרָעֶנָּה קִטְנִית מִפְּנֵי שֶׁהַקִּטְנִית שָׁם מַכְחֶשֶׁת אֶת הָאָרֶץ:
כסף משנה
9.
When a person rents a field with the stated intent of sowing barley, he should not sow wheat, because wheat saps the nutrients of the land more than barley. If he rented it with the intent of sowing wheat, he may sow barley.
If his original intent was to sow legumes, he may not sow grain. If his original intent was grain, he may sow legumes. In Babylon and lands of that nature, he should not sow legumes, for legumes sap the nutrients of the land.

הלכה י
הַמְקַבֵּל שָׂדֶה מֵחֲבֵרוֹ לְשָׁנִים מוּעָטוֹת אֵין לַמְקַבֵּל כְּלוּם בְּקוֹרַת הַשִּׁקְמָה וְכַיּוֹצֵא בָּהּ וְלֹא בְּשֶׁבַח הָאִילָנוֹת שֶׁיָּצְאוּ מֵאֲלֵיהֶן בַּשָּׂדֶה. אֲבָל מְחַשְּׁבִין לוֹ מְקוֹם הָאִילָנוֹת כְּאִלּוּ הָיָה בָּהֶן אוֹתוֹ זֶרַע שֶׁזָּרַע בְּכָל הַשָּׂדֶה. וְהוּא שֶׁצָּמְחוּ הָאִילָנוֹת בְּמָקוֹם הָרָאוּי לִזְרִיעָה אֲבָל אִם יָצְאוּ בְּמָקוֹם שֶׁאֵינוֹ רָאוּי לִזְרִיעָה אֵין מְחַשְּׁבִין לוֹ כְּלוּם. וְאִם קִבְּלָהּ שֶׁבַע שָׁנִים אוֹ יֶתֶר יֵשׁ לוֹ בְּקוֹרַת הַשִּׁקְמָה וְכַיּוֹצֵא בָּהּ. הִגִּיעַ זְמַנּוֹ לְהִסְתַּלֵּק מִן הַשָּׂדֶה וְהָיוּ שָׁם זְרָעִים שֶׁעֲדַיִן לֹא הִגִּיעוּ לְהִמָּכֵר אוֹ שֶׁנִּגְמְרוּ וְלֹא הִגִּיעַ יוֹם הַשּׁוּק לְמָכְרָן שָׁמִין אוֹתָן וְנוֹטֵל מִבַּעַל הַקַּרְקַע. כְּשֵׁם שֶׁחוֹלְקִין הַמְקַבֵּל וּבַעַל הַקַּרְקַע בַּתְּבוּאָה כָּךְ חוֹלְקִין בַּתֶּבֶן וּבַקַּשׁ. כְּשֵׁם שֶׁחוֹלְקִין בַּיַּיִן כָּךְ חוֹלְקִין בַּזְּמוֹרוֹת. אֲבָל הַקָּנִים הַמַּעֲמִידִים תַּחַת הַגְּפָנִים אִם קָנוּ אוֹתָן בְּשֻׁתָּפוּת הֲרֵי אֵלּוּ חוֹלְקִין בָּהֶן וְאִם הֵן מִשֶּׁל אֶחָד מֵהֶן זֶה שֶׁקָּנָה אוֹתָן הֲרֵי הֵן שֶׁלּוֹ. וְכֵן כָּל כַּיּוֹצֵא בָּזֶה:
כסף משנה
10.
When a person rents a field from a colleague for a few years according to a sharecropping agreement, the sharecropper does not receive a share of the wood that grows from the wild fig trees and the like, nor in the appreciation in the value of the field due to the trees growing in the field. We do, however, consider the place of the trees as if it were filled with the type of crop that was planted in the field. This applies provided the trees grew in a place that is fit to sow. If, however, they grow in a place that is not fit to sow, the sharecropper is not given any consideration. If the sharecropper rents the field for seven years or more, he is entitled to a share of the wood that grows from the wild fig trees and the like.
If at the time the sharecropper's lease runs out, there are plants in the field that have not reached the stage at which they are fit to be sold, or they have reached that stage, but the market day has not come yet, they should be evaluated and the sharecropper given his share by the owner of the land.
In the same manner as the sharecropper and the owner divide the grain; so, too, they should divide the straw and the stubble. In the same manner as they divide the wine; so, too, they should divide the twigs. Different rules apply with regard to the rods that are placed beneath the vine for support. If they were purchased in partnership, they should be divided in the same manner. If they were purchased by one party, they belong to the one who purchased them. Similar principles apply in all analogous situations.

הלכה יא
הַמְקַבֵּל שָׂדֶה מֵחֲבֵרוֹ לִטַּע מְקַבֵּל עָלָיו בַּעַל הַשָּׂדֶה עֲשָׂרָה בּוֹרְאוֹת לִסְאָה. יֶתֶר עַל זֶה מְגַלְגְּלִין עָלָיו אֶת הַכּל:
כסף משנה
11.
When a person rents a field from a colleague according to a sharecropping agreement in order to plant vines, the owner accepts the possibility that there will be ten non-productive vines in an area sufficient to grow a se'ah of grain. If there are more non-productive vines, the sharecropper must pay for the entire area as if all the vines were productive.

הלכה יב
הַמְקַבֵּל שָׂדֶה מֵחֲבֵרוֹ וְלֹא עָשְׂתָה אִם יֵשׁ בָּהּ כְּדֵי שֶׁתּוֹצִיא סָאתַיִם יֶתֶר עַל הַהוֹצָאָה חַיָּב הַמְקַבֵּל לִטָּפֵל בָּהּ. שֶׁכָּךְ כּוֹתֵב לְבַעַל הַקַּרְקַע אָנָּא אֵיקוּם וְאָנִיר וְאֶזְרַע וְאֶקְצֹר וְאֶעֱמֹר וְאָדוּשׁ וְאֶזְרֶה וְאַעֲמִיד כְּרִי לְפָנֶיךָ וְתִטּל אֶת חֶצְיוֹ אוֹ מַה שֶּׁיִּתְּנוּ וַאֲנִי אֶטּל הַשְּׁאָר בִּשְׂכַר עֲמָלִי וּבְמַה שֶּׁהוֹצֵאתִי:
כסף משנה
12.
The following rules apply when a person rents a field from a colleague under a sharecropping agreement and the field does not produce a significant yield. If its yield appears sufficient to produce at least two se'ah more than the investment made in it, the sharecropper is obligated to take care of it. For in the sharecropping agreement, he promises the owner of the land: "I will rise, plow the land, sow it, reap it, tie it in sheaves, thresh it and make a grain heap before you, and you will receive half - or whatever other portion they agreed upon - and I will receive the remainder as payment for my work and the expenses that I undertook."

הלכה יג
הַמְקַבֵּל שָׂדֶה מֵחֲבֵרוֹ וְאַחַר שֶׁזָּכָה בָּהּ הוֹבִירָהּ שָׁמִין אוֹתָהּ כַּמָּה הִיא רְאוּיָה לַעֲשׂוֹת וְנוֹתֵן לוֹ חֶלְקוֹ שֶׁהָיָה מַגִּיעַ לוֹ. שֶׁכָּךְ כּוֹתֵב לְבַעַל הַקַּרְקַע אִם אוֹבִיר וְלֹא אַעֲבִיד אֲשַׁלֵּם בְּמֵיטָבָא. וְהוּא הַדִּין אִם הוֹבִיר מִקְצָתָהּ. וּמִפְּנֵי מָה נִתְחַיֵּב לְשַׁלֵּם מִפְּנֵי שֶׁלֹּא פָּסַק עַל עַצְמוֹ דָּבָר קָצוּב כְּדֵי שֶׁנֹּאמַר הֲרֵי הִיא כְּאַסְמַכְתָּא אֶלָּא הִתְנָה שֶׁיְּשַׁלֵּם בְּמֵיטָבָא וּלְפִיכָךְ גָּמַר וְשִׁעְבֵּד עַצְמוֹ. אֲבָל אִם אָמַר אִם אוֹבִיר וְלֹא אַעֲבִיד אֶתֵּן לְךָ מֵאָה דִּינָרִין הֲרֵי זוֹ אַסְמַכְתָּא וְאֵינוֹ חַיָּב לְשַׁלֵּם אֶלָּא נוֹתֵן כְּפִי מַה שֶּׁרְאוּיָה לַעֲשׂוֹת בִּלְבַד:
כסף משנה
13.
The following rule applies when a person rents a field from a colleague under a sharecropping agreement, and after taking possession of the field decides to leave it fallow. We evaluate the amount the field could be expected to produce and require the sharecropper to give the owner the portion agreed upon. For in the sharecropping agreement, he promises the owner of the land: "If I leave it fallow and do not till it, I will pay according to its best yield." The same rule applies if he left only a portion of it fallow.
Why is the renter obligated to pay? Because he did not stipulate that he would pay a fixed amount, in which instance we would say that it is an asmachta, but instead promised to pay the field's best yield. Therefore, he made a binding commitment.
If, however, he stipulated: "If I leave it fallow, I will pay you 100 dinarim" this is considered an asmachta and he is not obligated to pay that amount. Instead, he should give the owner only his share of what the field would be expected to produce.

הלכה יד
הַמְקַבֵּל שָׂדֶה לְזָרְעָהּ שֻׁמְשְׁמִין וּזְרָעָהּ חִטִּים וְעָשְׂתָה חִטִּים שֶׁשָּׁוִין כַּמָּה שֶׁהִיא רְאוּיָה לַעֲשׂוֹת מִן הַשֻּׁמְשְׁמִין אֵין לוֹ עָלָיו אֶלָּא תַּרְעֹמֶת. עָשְׂתָה פָּחוֹת מִמַּה שֶּׁהִיא רְאוּיָה לַעֲשׂוֹת מִן הַשֻּׁמְשְׁמִין מְשַׁלֵּם לוֹ הַמְקַבֵּל כְּפִי מַה שֶּׁהִיא רְאוּיָה לַעֲשׂוֹת מִן הַשֻּׁמְשְׁמִין. עָשְׂתָה חִטִּים יֶתֶר מִמַּה שֶּׁהִיא רְאוּיָה לַעֲשׂוֹת מִן הַשֻּׁמְשְׁמִין חוֹלְקִין לְפִי הַתְּנַאי שֶׁבֵּינֵיהֶן אַף עַל פִּי שֶׁמִּשְׂתַּכֵּר בַּעַל הַקַּרְקַע:
כסף משנה
14.
The following rule applies when a person rents a field from a colleague under a sharecropping agreement with the intent of sowing sesame seeds, but instead, sows wheat. If the field produces a crop of wheat that is worth the same as the yield of sesame seeds could have been expected to be worth, the owner may have no more than complaints against him.
If the field produces a crop of wheat that is worth less than the yield of sesame seeds could have been expected to be worth, the sharecropper must pay the amount the crop of sesame seeds could have expected to yield. If the field produces a crop of wheat that is worth more than the yield of sesame seeds could have been expected to be worth, they should divide the crop according to their original stipulation although the owner of the land profits.

משפטים הלכות שכירות פרק ח
Mishpatim Schirus Chapter 8