Establishment and Nodulation of Arrowleaf Clover 1

We need information on effects of planting depths and inoculation methods on stand, nodulation, and early plant development for establishing temperate, small‐seeded annual legumes. Arrowleaf clover ( Trifolium vesiculosum Savi ‘Yuchi’) plantings from uninoculated and water or commercial sticker inoculated seed were made at depths of 0, 10, 25, and 40 mm with and without irrigation immediately following planting, on a Udertic Haplustoll soil. Seedling and nodule numbers, and biomass (plant top and root weights) were determined in eight environmental periods. Regression testing and curve fitting of unequal planting depth increments and plant trait measurement were made with a special set of orthogonal polynomial coefficients. Nodulation maximums were at greater planting depths (19 and 22 mm) than seedling number maximums (6 and 10 mm) in early and pooled irrigation blocks, respectively. Number of plants and nodules per plant were optimum at the balanced compromise depth of 13 mm and in a range of 10 to 30 mm for early irrigation. With pooled irrigation or simulated dryland planting the balanced compromise point was 16 mm and the range 10 to 25 mm for optimizing planting depths. Surface or 40 mm depths were hazards to establishment of the small‐seeded legume, and its rhizobium. Pelgel sticker significantly increased nodulation over water sticker and the untreated check with early irrigation at 0 and 10 mm planting depths, but in all irrigation treatments nodule numbers were increased by pelgel sticker only in plantings at 10 mm depth. Biomass and plant number were significantly correlated under both early and delayed irrigation treatments (0.95 and 0.98, respectively) due to poor growth environment.