Blind Inlets: A Conservation Practice to Reduce Pesticide, Sediment, and Nutrient Loadings from Small Depressions in Fields.

Fertilizers and pesticides are common inputs to increase soil productivity; however, there are environmental concerns due to losses of these inputs from agricultural fields to water bodies.

Developing and/or modifying existing conservation practices (CPs) to mitigate contaminant losses is necessary. Typically, in the US Midwest, tile risers are used to drain excess water from small depressions in fields. Potentially, water drained from depressions would be improved by passing through a media to reduce the maximum flow rate , nutrient, and pesticide total losses without effecting crop yield. The blind inlet has been approved by the USDA-NRCS as a CP to reduce nutrients losses.

In an agricultural field in Northeast Indiana, risers and blind inlets were installed to drain two small depressions (ADE and ADW). Our experimental design was implemented in such a way that ADE and/or ADW will drain either through the riser or the blind inlet. Then, water samples were automatically collected during runoff events.  These samples were collected for 6 years (from 2008 to 2013) and analyzed for pesticides including atrazine, glyphosate, metolachlor, 2, 4-D (after 2010), total N (total oxidyzable N + total Kjeldahl N), total P, and sediment losses.

The results of this 6-year study show that the blind inlet reduced loadings of the pesticides analyzed, total N and P, and sediments compared to the riser.  Cumulative losses of atrazine and 2, 4-D were reduced by 50 and 55%, respectively, whereas metolachlor and glyphosate where reduced by 26 and 9%, respectively.  The cumulative losses of total N and P were reduced by 32 and 24%, respectively; whereas for sediment, cumulative losses were reduced by 50%. Based on these results, blind inlets appear to be an effective means at decreasing pesticide, total N and P and sediment losses from agricultural fields to receiving waters.