Planting Date and Seeding Rate Effects on White Lupin Yield in Alabama and Virginia

Abstract

White lupin (Lupinus albus L.) has high potential as a winter grain (33 bu/acre), silage (15 tons/acre), wildlife, and cover crop in the southeastern USA. Management recommendations have to be developed for producers. We examined planting date and seeding rate effects on grain and biomass yield in winter-type white lupin. From 1991 to 1993, seeds were sown in north Alabama on a Wynnville fine sandy loam (fine-loamy, siliceous, thermic, Glossic Fragiudult), in central Alabama on a Norfolk sandy loam (fine-loamy, kaolinitic, thermic, Typic Kandiudult), and in south Alabama on a Lucedale fine sandy loam (fine-loamy, siliceous, thermic, Rhodic Paleudult). In 1994 and 1995, a study was sown in north Virginia on a Davidson silty clay (clayey, kaolintic, thermic, Rhodic Kandiudult). Treatments were three planting dates, three seeding rates (35 000, 70 000, and 105 000 seeds/acre) and two to five cultivars in Alabama. In Virginia, one or two cultivars were sown on three planting dates at 70 000 seeds/acre. Grain yield in 1995 in north Virginia averaged 60 bu/acre while the Alabama locations were less than 30 bu/acre. These differences are due to the more moderate, maritime climate in north Virginia. The second planting date and middle seeding rate produced acceptable grain yield across environments; we advise higher seeding rates for delayed planting. The highest biomass yields were achieved at earlier planting dates and the highest seeding rate. Based on these recommendations, producers should obtain acceptable grain, silage, wildlife, and cover crop yields. Problem Although white lupin is not yet a commercial crop in the southern USA, it has potential as a grain and silage crop, as a wildlife feed, and as a cover crop. Planting date and seeding rate information is needed to optimize production practices. Background White lupin is a self-pollinated, large-seeded legume, native to the Mediterranean region. Over the past 2000 to 3000 yr, white lupin has been cultivated as a minor grain and cover crop. The minor crop status has resulted in very little breeding effort toward improvement of white lupin as an agronomic crop. In spite of this, white lupin shows considerable promise as a winter grain crop in the southeastern USA; grain yields in experimental trials from 1987 to 1989 averaged 33 bu/acre. Most crops are susceptible to low temperatures during the seedling and flowering stages. It is imperative, therefore, to establish seeding dates which enable plants to escape low temperatures during critical phases of development. Study Description We established seeding date experiments at three locations in Alabama, and at one location in Virginia. The latest seeding date coincided with the average date of the first 28°F temperature at each location in Alabama. In Alabama, we also seeded lupin at 4 and 8 wk prior to that date so the time for seeding could be determined for each location. In Virginia, seeding dates were made 2, 4, and 5 wk prior to the first 28°F temperature. For the Alabama locations, we also seeded each date at rates of 35 000, 70 000, and 105 000 seeds/acre, whereas in Virginia only the 70 000 rate was used. Rows were seeded 36 in. apart in Alabama and 12 in. apart in Virginia. The center rows of each four-row plot were hand-harvested for grain yield (bu/acre at 58 lb/bu and corrected to 13% moisture). Total biomass yield was also measured in Alabama. Applied Questions Does planting date affect grain yield? Yes, it certainly does. The optimum planting date was the middle date at all locations. Early seeding at more northern locations reduced grain yields in some cultivars because (i) plants developed too much biomass before the onset of winter, resulting in the destruction of the growing point on the main axis, and (ii) plants were damaged by late-winter freezes caused by bolting too early in late winter. In south Alabama, delayed seeding resulted in reduced grain yield because the steep temperature increase in late April limited pod set. White lupin is a cool season crop that does not perform well at higher temperatures. Does seeding rate affect grain yield? It depends. With a wide row spacing at the optimum (middle) planting date, seeding rate had little effect on grain yield, although total biomass yield increased substantially with seeding rate, irrespective of planting date. This biomass yield increase could be important when lupin is used as a silage or cover crop. Increasing seeding rates at the latest planting date increased both grain and biomass yields, thus overcoming some of the effects of smaller plants associated with the latest planting dates. What is the recommendation for producers? Seed approximately 4 wk prior to the average date of the first 28°F temperature; your local county extension personnel will be able to determine this date for you. If you have to delay planting, increase the seeding rate.