SOYBEAN DEVELOPMENT IS AFFECTED BY METHOD AND TIMING OF RYE CONTROL IN COVER CROP SYSTEMS

Authors: WESTGATE, LESLIE - IA STATE UNIVERSITY; Singer, Jeremy

Submitted to: Journal of Natural Resources and Life Sciences Education
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/15/2005
Publication Date: 2/25/2005
Citation: Westgate, L.R., Singer, J.W., 2005. Soybean development is affected by method and timing of rye control in cover crop systems. Journal of Natural Resources and Life Sciences Education. 34:17-21.

Interpretive Summary: Cover crops provide environmental and soil quality benefits, yet their adoption into production agriculture has been limited. This study was conducted to determine whether differences exist in soybean water use, light interception, and development following a rye cover crop to provide management information that may increase rye cover crop adoption. The effects of mechanical and chemical rye control at different growth stages was investigated near Boone, IA in 2002 and 2003. Regrowth from mechanical rye control in 2002 depleted soil water until rye matured. Light interception by soybean was reduced when rye was controlled early because of rye regrowth. Soybean dry matter was greater when rye was chemically versus mecahnically controlled in one year and similar in the other. However, almost all treatments with rye had lower dry matter accumulation than the control. Rye delayed pod maturity in both years compared to the control. Soybean producers who adopt these methods of rye management can expect delayed soybean maturity and reduced dry matter accumulation. This information will be of use to extention agents and producers.

Technical Abstract: Cover crops provide many environmental and soil quality benefits, yet their adoption into production agriculture has been limited by insufficient management information. This study was conducted to determine a combination of method and timing of rye (Secale cereale L.) control that would not hinder soybean [Glycine max (L.) Merr.] growth or result in resource competition. The effects of mechanical and chemical rye control at 2nd node, boot, and anthesis growth stages on soil water, light interception, soybean growth and maturity were investigated near Boone, IA, on Spillville loam (Fine-loamy, mixed, superactive, mesic Cumulic Hapludolls), and Clarion loam (Fine-loamy, mixed, superactive, mesic Typic Hapludolls) in the 2002 and 2003 growing seasons. In 2002, untimely rainfall reduced soil water 0.0325 kg/kg from 2nd node to anthesis in the 0-15 cm depth in chemical control. In mechanical control, rye depleted soil water until it matured, at which point larger plants in check subplots utilized soil water at a higher rate than soybean in treatments with rye. Soybean light interception was reduced by rye in mechanical treatments in both years. Anthesis and check plots in chemical control had similar values for light interception. Biomass accumulation was lower under mechanical control than chemical control. However, even the best treatment in chemical control, anthesis, accumulated 140 g/m**2 less biomass than check treatments in 2002. All treatments containing rye delayed maturity. Anthesis timing matured closest to check subplots at 6.5 and 3.8 days after the check in 2002 and 2003, respectively. The possibility of allelopathy delaying maturity is worthy of further investigation. Chemical control at anthesis was the most effective management system after the check, differing significantly only in date of maturity. Periods of low rainfall, ineffective rye control, and possible allelopathy were critical limiting factors in this rye cover crop system.