Spin Ditch Filter Strips Impact on Nutrient and Sediment Load.

Lake St. Josef, located in Tensas Parish, LA was added to the EPA’s 303(d) list for impairment due to excess nutrients and sediment load. Primary land use for the area includes row crop production which, traditionally, leaves the soil surface bare resulting in significant losses of soil and nutrients and the decline in water quality of surrounding water bodies. These impaired lakes and streams have prompted the exploration and implementation of best management practices designed to reduce both environmental and financial losses to the producer. In 2014, drainage or ‘spin’ ditches, designed to remove excess moisture from the soil surface, were planted with rye or wheat to serve as filter strips between a soybean field and Lake St. Joseph. In 2015, filters were planted over with wheat, at two widths (4.6 m and 9.1 m). Water quality samples were collected following rainfall events for analyses at the terminal end of each strip as well as from Lake St. Joseph. Water quality has significantly improved in the main body of the lake since it was added with increasing dissolved oxygen (>5.0 mg L^-1) and decreasing total phosphorus, total suspended solids, and biological oxygen demand. In 2014, filters, regardless of species, decreased total suspended solids (TSS; 57%), orthophosphate-P (37%), and total Kjedahl N (39%) compared to bare ground controls. Field and weather conditions in the winter of 2015-2016 resulted in a reduced number of samples, however first flush samples indicated a decrease in TSS (54%), orthophosphate-P (50%), Total P (44%), and ammonium-N (65%) regardless of filter size. The 9.1 m filter strip reduced nitrate-N in first flush samples by 122%. Overall, the inclusion of best management practices like ‘spin-ditch’ filter strips have aided in improved water quality in Lake St. Joseph.