Yahya related to me from Malik that he had heard that Umar ibnAbd 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 morefor the purchaser. Anything less is not counted as crop damage."
USC-MSA web (English) reference: Book 31, Hadith 16
Arabic reference: Book 31, Hadith 1309