Weed Control in No-till Organic Soybean.

Most producers of organic soybean [Glycine max (L.) Merrill] invoke tillage as an essential part of their weed management plan in this herbicide-free context.  Unfortunately, reliance on tillage demands labor and fuel inputs, may exacerbate soil losses due to erosion and CO₂ efflux to the atmosphere, and sometimes fail to control key weed species.  The objective of this research was to determine the utility of no-till methods for control of weeds in organic soybean.  Soybean was planted following organically-grown winter rye using a front-mounted roller system and a rear-mounted no-till planter; in addition, soybean was planted using conventional tillage (moldboard plowing followed by disking) in adjacent blocks.  At two week intervals after planting (WAP), all visible weeds were removed at the soil surface by hand-hoeing from appropriate 3.0 m wide by 6.1 m long plots (four rows spaced 0.75 m apart) in order to impose the following treatments:  check (no hand-hoeing), 2 WAP (weed-free through 2weeks), 4   WAP (weed-free through 4 weeks), 6 WAP (weed-free through 6 weeks), and 8 WAP (weed-free through 8 weeks).  No additional hand-hoeing was imposed beyond the designated period of weeks.  At physiological maturity of soybean, biomass samples were collected from a 0.38 m² area for soybean, grassy weeds, and broadleaved weeds.  Yields and yield components of soybean will also be reported.  This study provides important insight into the dynamics of weed management in organic no-till soybean.