Management studies must be conducted to realize the full potential of white lupin (Lupinus albus L.) as a grain crop for the southeastern USA. This experiment examined planting date, row spacing, and seeding rate effects on grain and biomass yield of spring-sown white lupin. In 1991 and 1992, field studies were conducted in northern Alabama on a Wynnville fine sandy loam (fine-loamy, siliceous, thermic GIossic Fragiudult), in central Alabama on a Hiwassee sandy loam (clayey, kaolinitic, thermic Typic Kanhapludult), and in southern Alabama on a Lucedale fine sandy loam (fine-loamy, siliceous, thermic Rhodic Paleudult). Treatments included three planting dates, three row spacings (17.5, 35, and 70 cm), three seeding rates (17.5, 35, and 52.5 seeds m−1), and two cultivars (Primorsky and Ultra). Prevailing weather allowed only one planting date in northern Alabama in 1991 and 1992. In the second year of the study, only one and two plantings were successful in central and southern Alabama, respectively. Grain yields averaged 551 kg ha−1 in 1991 and 604 kg ha−1 in 1992. Grain and biomass yield was always highest in northern Alabama. Planting date affected grain and biomass yield the most in central and southern Alabama in 1991. Decreased row spacing increased grain yields as much as 10 kg ha−1 per unit decrease in spacing. Grain yields increased as much as 19 kg ha−1 for every unit increase in seeding rate. Principal component analysis of yield components created factors branch, seed mass, and mainstem, which accounted for 57, 23, and 14% of the original variance, respectively. Factors branch and mainstem were highly correlated (r < 0.75) with grain and biomass yield. Seed mass and mainstem were highly correlated with harvest index (r < 0.65). For the southeastern USA, high yields in spring-sown white lupin will require (i) early seeding, (ii) narrow row spacing, and (iii) high seeding rates.
Research supported in part by Hatch funds allocated to Alabama Agric. Exp. Stn. Project no. ALA-03-005 and by funds from the Wheat and Feed Grain Committee of the Alabama Farmers Federation.