Monday, November 13, 2006

Self-seeding Small Grain Cover Crop in a Soybean-Corn Rotation.

Paul McDonald, Iowa State University, Ames, IA 50010, Jeremy W. Singer, National Soil Tilth Lab., 2150 Pammel Dr., Ames, IA 50011-4420, and Mary H. Wiedenhoeft, Iowa State Univ., Iowa State Univ., Ames, IA 50011-1010.

Cover crops provide environmental benefits, yet adoption in agronomic farming systems is low.  Winter rye (Secale cereale L.), wheat (Triticum aestivum L.), and triticale (X Triticosecale Wittmack) were used to develop self-seeding cover crop systems in a soybean [Glycine max (L.) Merr.]-corn (Zea mays L.) rotation. Winter cereals were seeded in two or four 19 cm rows between each future 76 cm soybean row.  Management systems in soybean were a no cover crop check, four rows with early (4RE) and late (4RL) spring glyphosate to eliminate two rows adjacent to the soybean row and mechanical control, four rows with mechanical control (4R) only, two rows with mechanical control (2R), and two rows with no mechanical control (2RNC).  These residual treatments were managed in corn the following year to promote self-seeding using chemical and mechanical control.  During the corn year wheat and triticale shoot biomass at maturity was similar among management systems (51 g m-2).  In rye, the 2RNC treatment produced the greatest biomass (56 g m-2) at maturity, while the 4RE, 4R, and 2R were similar (19 g m-2). Corn grain yield was affected by management system, but not species.  Yield decreased 9-12% in the 4RL, 4RE, and 2R treatments and 18-22% in the 4R and 2RNC treatments compared to the check (10.3 Mg ha-1).  Although self-seeding of the cover crop was successful, competition from cover crop regrowth lowered corn yields.