Coal mine subsidence: Effects of mitigation on crop yields

Subsidence from longwall underground coal mining adversely impacts agricultural land by creating wet or ponded areas. While most subsided areas show little impact, some localized places, usually less than 1.5 ha in size, may experience total crop failure. Coal companies mitigate subsidence damaged cropland by installing drainage waterways or by adding fill material to raise the grade. The objective of this study was to test the effectiveness of mitigation in restoring com and soybean yields to pre-mined levels. Fourteen sites in southern Illinois were selected for study. Corn (Zea mays L) and soybean (Glycine max L.) yields from mitigated and nearby undisturbed areas were compared for four years. Results varied due to differing weather and site conditions. Mean corn yields overall, however were significantly (a=0.05) lower on mitigated areas. There was no significant difference in overall mean soybean yields. Soil fertility levels were similar and did not account for yield differences.