Evaluation of Weed Management Practices in White Lupin (Lupinus albus L.)

Abstract

Worldwide, 450 lupin species can be found with 4 species currently grown. The cultivated species consist of three old world species white lupin (Lupinus albus L.), yellow lupin (L. luteus L.) and blue lupin (L. angustifolius L.) and the new world species Andean lupin (L. mutabilis Sweet). Between 1930 and 1950 lupins were grown on 1 million ha in the Southeastern United States. The US lupin production declined after the 1950s for various reasons including: 1). discontinued government support for green-manure, 2) N-fertilizers became affordable and 3) early freezes during two consecutive years that severely reduced seed stock. White lupin is of major interest in the southeastern USA because winter hardy cultivars are available. White lupin grows best on well drained sandy loams, loamy soils and sands and tolerates a pH range of 5.5 to 6.8. Except for the Black Belt, most soils in Alabama fulfill these requirements. White lupin is a poor weed competitor during its early establishment which makes effective weed control necessary. Therefore, the objectives of this experiment are to investigate various weed management practices and evaluate their effect on weed control and white lupin performance (plant density, crop injury, yield, height and yield components). A two-year experiment was established at the Field Crops Unit as well as the Plant Breeding Unit, E. V. Smith Research and Extension Center of the Alabama Agricultural Experiment Station near Shorter, AL. Our treatments included ten PRE-applied herbicides, nine POST-applied herbicides well as organic treatments (2 cover crop living mulch, 2 mechanical weed control practices). Response variables measured were weed control, crop injury, plant density, grain yield, seed mass, plant height, number of yield components and seed yield per plant. Over the course of the experiment 14 weed species were encountered. Best control (>80%) of the most troublesome weed species, i.e. henbit (Lamium amplexicaule L.), Carolina geranium (Geranium carolinianum L.), wild radish (Raphanus raphanistrum L.) and corn spurry (Spergula avensis L.) was achieved with PRE applied diclosulam, metribuzin, pendimethalin, imazethapyr, S-metolachlor, and a mixture of S-metolachlor/linuron. Good control (>90%) of annual ryegrass (Lolium multiflorum Lam.) and annual bluegrass (Poa annua L.) by POST-applied herbicides was achieved by sethoxydim and fluazifop. More than 80% non-selective weed control was achieved by the POST-applied glyphosate. PRE-applied diclosulam and flumioxazin resulted in unacceptable crop injury and subsequent yield loss in both years. POST-applied thifensulfuron and chlorimuron caused complete crop injury (death) of all three cultivars which resulted in crop density reduction and severe yield loss in 2007. Hence these herbicides were excluded in study year 2008. The application of glyphosate lead to inacceptable crop injury and significant yield reduction, but did not significantly reduce crop density. Diclosulam, fomesafen and glyphosate significantly reduced lupin height, number of fruiting branches and seed yield. Summing up, it can be stated that the chemical treatments [S-metolachlor/linuron mixture, pendimethalin, imazethapyr (PRE and POST), 2,4-DB, sethoxydim and fluazifop] and all organic treatments offered good weed control without causing inacceptable crop injury and yield loss. However, our data showed that the lupin cultivars yielded well even without the use of weed control practices.