אורח חיים פ״בOrach Chayim 82

Se’if 1א׳

צוֹאָה יְבֵשָׁה כָּל כָּךְ, שֶׁאִם יִזְרְקֶנָּה תִּתְפָּרֵךְ, הֲרֵי הִיא כְּעָפָר, וּמֻתָּר לִקְרוֹת כְּנֶגְדָּהּ, וְהוּא שֶׁלֹּא יְהֵא בָּהּ רֵיחַ רַע: הַגָּה: וְיֵשׁ אוֹמְרִים דְּלָא הָוֵי כְּעָפָר, רַק אִם נִפְרֶכֶת עַל יְדֵי גְּלִילָה בְּלֹא זְרִיקָה, וְכֵן עִקָּר (רַשִׁ"י וְהָרֹא"שׁ פֶּרֶק מִי שֶׁמֵּתוֹ וְטוּר).

The Laws of Dry Excrement, containing 2 s'ifim Excrement which is so dry that if one throws it, it crumbles apart, behold it is like dirt and it is permitted to recite [the Sh'ma] in front of it. And this is if it does not have a bad smell. Rem"a: There are those who say that it is not like dirt unless it crumbles when rolled without throwing it, and such is the correct [opinion] (Rashi and the Rosh on chapter "Mi sheMeito" and Tur)

Se’if 2ב׳

מֵי רַגְלַיִם שֶׁנִּבְלְעוּ בַּקַּרְקַע, אִם הָיוּ מַרְטִיבִין הַיָּד, אָסוּר לִקְרוֹת כְּנֶגְדָּהּ (וְיֵשׁ אוֹמְרִים דְּאֵינוֹ אָסוּר רַק בְּטוֹפֵחַ עַל מְנַת לְהַטְפִּיחַ וְיֵשׁ לִסְמֹךְ עַל זֶה):

Urine that was absorbed into the ground - if it [could] moisten the hand, it is forbidden to recite in front of it. Rem"a: And there are those who say that it is not forbidden unless it is moist enough to moisten another thing, which in turn can moisten another thing. And one may rely on this [opinion].