Evaluating Postharvest Sugarcane Residue Amendment and Broadcast Fertilizer Application as Techniques to Enhance Dune Grass Establishment and Expansion

Abstract

Coastal dunes are valuable components of barrier shorelines, but establishing the appropriate vegetation to facilitate the growth and maintenance of this important habitat is difficult due to the presence of consistent stressors, including nutrient, water limitation, and salt spray. We examined whether the amendment of dune soils with postharvest sugarcane residue and broadcast fertilizer would enhance the establishment and growth of two key dune grass species, bitter panicum (Panicum amarum) and sea oats (Uniola paniculata), in natural and created sand dunes in coastal Louisiana in a short-term field study. The benefit of broadcast fertilizer addition to the growth of both species was evident, as was a tendency for greater establishment and growth of bitter panicum than sea oats. The created dune environment was significantly less favorable than the natural dune system in terms of soil characteristics and plant growth responses. Interestingly, postharvest sugarcane residue, which we hypothesized would improve dune grass establishment and growth by increasing soil organic matter and thereby soil moisture retention, failed to enhance dune grass growth. We conclude that dune restoration efforts in coastal Louisiana would benefit from the inclusion of a broadcast fertilizer regime, particularly in terms of accelerating bitter panicum growth and establishment. However, application of postharvest sugarcane residue does not appear to provide the same benefits to dune grass establishment and expansion as has been shown with other organic amendments.