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ARS Home » Plains Area » Brookings, South Dakota » Integrated Cropping Systems Research » Research » Publications at this Location » Publication #323471
Title: Impact of preceding crop on alfalfa competitiveness with weeds

Author
item Anderson, Randal

Submitted to: Renewable Agriculture and Food Systems
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/11/2016
Publication Date: 1/27/2017
Citation: Anderson, R.L. 2017. Impact of preceding crop on alfalfa competitiveness with weeds. Renewable Agriculture and Food Systems. 32:28-32.

Interpretive Summary: Organic producers are interested in no-till practices in their farming systems. To help organic producers include no-till in their farming system, we are examining a complex rotation that includes a 3-year sequence of alfalfa. In this study, we showed that establishing alfalfa after soybean is the most favorable for suppressing weeds in alfalfa. Weed biomass was higher in alfalfa following spring wheat or corn. Density of alfalfa was highest when following soybean, which increased alfalfa competitiveness with weeds. Alfalfa yield was also higher following soybean than either corn or spring wheat. Increasing alfalfa competitiveness with weeds will enhance the potential for a continuous no-till system in organic farming.

Technical Abstract: Organic producers would like to include no-till practices in their farming systems. We are seeking to develop a continuous no-till system for organic farming, based on a complex rotation that includes a 3-year sequence of alfalfa. In this study, we evaluated impact of preceding crop on weed infestation in alfalfa. Alfalfa was established with no-till following spring wheat, corn, or soybean. The study involved a 4-year interval, with weed dynamics measured in the fourth year. Alfalfa established after soybean suppressed weeds more than alfalfa established after spring wheat or corn. Weed biomass in alfalfa following spring wheat was 18% of the plant community, but only 1% when alfalfa followed soybean and 6% when alfalfa followed corn. Weed biomass increased because alfalfa density following spring wheat was only 71% of alfalfa following soybean. Weeds such as downy brome and dandelion were able to establish and produce biomass where alfalfa stand was sparse. Alfalfa forage yield across three years was also higher following soybean than either spring wheat or corn. Alfalfa competitiveness with weeds can be improved by choice of preceding crop.