Overcoming the natural resistance of plant cell walls to deconstruction, known as recalcitrance, is a major bottleneck to cost-effective biofuel production. In response, scientists modified lignin. Lignin is one of the polymers responsible for recalcitrance and crucial for structural support within plant tissues. Modifying lignin improved the conversion of plant biomass to fuel. Yet a question remained. Will specifically modified bioenergy crops negatively impact the local soil? In field studies, researchers confirmed that growing genetically manipulated switchgrass as no negative effects on soils over the short terms studied (2 to 5 years).