The effect of harvest date and inoculation on the yield and fermentation characteristics of two varieties of white lupin (Lupinus albus) when ensiled as a whole-crop

An experiment was conducted to determine the ensiling potential of whole-crop white lupins (Lupinus albus). Three replicate 0.1 ha plots of an autumn variety (cv. Arthur) and a spring variety (cv. Nelly) were sown in spring and harvested at 12.5, 14.5, 16.5 and 18.5 weeks after sowing. Following yield determinations the forages were artificially wilted for a 24 h period, and sampled to determine chemical composition. Representative sub-samples of forage from each harvest were then ensiled in 10 kg mini-silos, either untreated or treated with an inoculant (Lactobacillus plantarum). The silos were opened after 97 days, and the ensiled forages sampled to determine chemical composition. The aerobic stability of the different silages was then determined over an 8-day period. The optimum growth stage for harvesting for both varieties occurred at 16.5 weeks after sowing. Although the fresh matter yield of Nelly was significantly higher than that of Arthur (47,590 kg ha−1 versus 36,580 kg ha−1), the dry matter (DM) yield of the two varieties was similar (overall mean 5953 kg DM ha−1). Choice of harvesting date significantly affected the DM, water-soluble carbohydrate (WSC), neutral-detergent fibre (NDF) and nitrate concentrations of the wilted forage, but did not influence the crude protein (CP) concentration or buffering capacity. The silages prepared from the Arthur variety had lower concentrations of CP (209 g kg−1 DM versus 229 g kg−1 DM), WSC (12.2 g kg−1 DM versus 16.3 g kg−1 DM) and free amino acids (FAA) (0.510 moles kg−1 DM versus 0.666 moles kg−1 DM) than those produced from Nelly. Between-harvest date differences in the concentrations of DM, ammonia-N, WSC, NDF, lactic acid, acetic acid and FAA of the lupin silage were observed, together with effects on dry matter digestibility. Inoculation was found to significantly reduce the pH and ammonia-N, acetic acid, FAA and CP concentrations, and increase the DM and WSC concentrations of the lupin silages. Effluent production and DM losses were higher for silages prepared from the Nelly variety, but the aerobic stability of the silages from the two varieties was similar. The results obtained indicate that white lupins can be successfully ensiled as a whole-crop, and that the application of an inoculant is beneficial. In terms of agronomy and silage composition the spring variety Nelly out-performed the autumn variety Arthur when both were sown in spring.