Caution: Translations of Quran and Ḥadīth may lead to possible misapplications and misinterpretations. This site is intended for students of sacred knowledge that are proficient in comprehending classical Arabic and have a strong foundation in Islamic sciences. Also note that religious injunctions rely on several aspects beyond what one may glean through reading individual aḥādīth.
malik:31-17

Yahya related to me from Malik that he had heard that Umar ibn Abd al-Aziz decided in a case to make a reduction for crop damage. Malik said, "That is what we do in the situation." Malik added, "Crop damage is whatever causes loss of a third or more for the purchaser. Anything less is not counted as crop damage."  

مالك:٣١-١٧وَحَدَّثَنِي عَنْ مَالِكٍ أَنَّهُ بَلَغَهُ أَنَّ عُمَرَ بْنَ عَبْدِ الْعَزِيزِ قَضَى بِوَضْعِ الْجَائِحَةِ قَالَ مَالِكٌ وَعَلَى ذَلِكَ الأَمْرُ عِنْدَنَا قَالَ مَالِكٌ وَالْجَائِحَةُ الَّتِي تُوضَعُ

عَنِ الْمُشْتَرِي الثُّلُثُ فَصَاعِدًا وَلاَ يَكُونُ مَا دُونَ ذَلِكَ جَائِحَةً