Comparing Environmental Impacts of No-till and Living Mulch Corn Production Systems Using Matched Watersheds.

Living mulch production systems take advantage of perennial legumes to supply N to row crops. White clover is has been used as a living mulch cover crop because of its perennial stoloniferous growth habit, traits which should reduce erosion and improve water quality.  Annual cover crops using no-till reduce water runoff and improve water quality, but there is little data comparing erosion and water quality parameters of the living mulch and annual cover crop systems.  A study was established to measure water runoff and quality in a white clover living mulch (LM) system and a cereal rye/no-till (CR) cover crop system using matched watersheds.  Corn was established in April, the CR crop received 250 kg ha^-1 N, but the WC crop received no N.  The corn was irrigated to maintain >40% water content, and harvested after physiological maturity.  The watersheds were sub-divided into four 0.4-ha paddocks with electric fencing which were sequentially grazed over a 28-d period.  Clover regrowth was quantified after grazing.  H-flumes were used to quantify and collect water, and quantified for sediment and E coli.  The LM watershed had reduced water runoff, sediment, and E. coli compared to CR.  Clover had rapid regrowth and provided 100% soil cover within 60 days after grazing.  Clover that was grazed immediately after harvest regrew faster than other clover paddocks.  Cattle grazing CR lost 0.39 and grazing LM gained 0.53 kg day^-1.