Runoff, sediment, nitrogen, and phosphorus losses from agricultural land converted to sweetgum and switchgrass bioenergy feedstock production in north Alabama

Renewable energy sources such as bioenergy crops have significant potential as alternatives to fossil fuels. Potential environmental problems arising from soil sediment and nutrient losses in runoff water from bioenergy crops need to be evaluated in order to determine the sustainability and overall feasibility of implementing bioenergy development strategies. This paper discusses runoff, sediment, N, and total P losses from agricultural land (continuous cotton ( Gossypium hirsutum L.)) converted to short-rotation sweetgum ( Liquidamber styraciflua L.) plantations with and without fescue ( Festuca elatior L.) and switchgrass ( Panicum virgatum L.) bioenergy crops, compared to corn ( Zea mays L.), on a Decatur silt loam soil in north Alabama, from 1995 to 1999. Runoff volume was significantly correlated to total rainfall and sediment yield in each year, but treatment differences were not significant. Sweetgum plots produced the highest mean sediment yield of up to 800 kg ha −1compared to corn and switchgrass plots, which averaged less than 200 kg ha −1. Runoff NH 4 + N losses averaged over treatments and years for spring season (3.1 kg ha −1) were three to five times those for summer, fall, and winter seasons. Runoff NO 3 − N for no-till corn and switchgrass plots in spring and summer were five to ten times that for sweetgum plots. No-till corn and switchgrass treatments had 2.4 and 2.1 kg ha −1 average runoff total P, respectively, which were two to three times that for sweetgum treatments. Growing sweetgum with a fescue cover crop provides significantly lower risk of water pollution from sediment, runoff NH 4 + N, and NO 3 − N.