Seed Scarification and a Companion Crop May Enhance Forage Legume Establishment in the Central West Regions of USA.

Interest has been increasing in the Central West regions of USA to grow forage legumes (e.g., sainfoin (Onobrychis viciifolia Scop.), cicer milkvetch (CMV; Astragalus cicer L.), and medic (Medicago rigidula (L.) All.) as alternative to alfalfa (Medicago sativa L.).  Establishment is a major concern associated with these legumes.  The objectives of this study were to determine the best method(s) to scarify seeds and evaluate the use of a companion crop to enhance establishment.  Scarification methods included heat (60°C for two hours), freeze-thaw (-80°C followed by 23°C for three cycles), mechanical (sand paper rubbed for five minutes), and acid scarification (sulfuric acid soaked for five minutes).  Seeds of several varieties from four legume species (alfalfa, sainfoin, CMV, and medic) were used.  The field study is being conducted at two locations (Lingle and Laramie) in Wyoming.  The experimental design was a RCBD with four replicates and the unit plot was 1.5m×6m.  One variety from each of the above four legume species was used.  In late spring 2009, the study was planted with oats (Avena sativa L.) as a companion crop.  Mechanical scarification worked best for CMV (e.g., reduction of hard seed from 77 to 33%) whereas acid scarification worked best for the medic seeds (hard seed from 23 to 1%).  Using oats as a companion crop seemed to improve seedling emergence and establishment of legumes.  This was evidenced by lower seedling count and dry matter (DM) yield of weeds in the plots with companion crop than the plots without companion crop (e.g., 1516 vs. 3195 kg DM/ha at Lingle, and 71 vs. 301 kg DM/ha at Laramie).  Data collected from spring through fall of 2010 will be included in the final presentation.