Effects of Variety and Seeding Rate on Performance of Sweet Lupin (Lupinus angustifolius) at Holetta, in the Central Highlands of Ethiopia

The study was executed to evaluate the agro-morphological and nutritional performance of four narrow-leafed blue sweet lupin varieties (Australian lupin, Probor, Sanabor, and Vitabor) sown with five seeding rates (60, 70, 80, 90, and 100 kg/ha) during the main cropping seasons of 2014 and 2015 at Holetta in the central highlands of Ethiopia. Randomized complete block design replicated three times in factorial arrangements was used for experimenting. The lupin varieties were sown in rows with an inter-row spacing of 30 cm. At sowing, diammonium phosphate fertilizer at the rate of 100 kg/ha was uniformly applied for all treatments in both years. Data were collected on plant height, dry matter yield, number of pods per plant, number of seeds per pod, seed yield, and nutritive value. All measured data were subjected to analysis of variance using procedures of SAS general linear model. The result revealed that plant height, number of pods per plant, and number of seeds per pod of lupin varieties were significantly (P<0.001) affected by experimental years. The varietal difference was the major cause of variation (P<0.05) for dry matter yield, the number of pods per plant, and seed yield. The Sanabor, Probor and Vitabor varieties had 38, 23, and 20% dry matter yield advantage over the introduced Australian lupin variety, respectively. The Sanabor variety which produced the highest seed yield had 25, 17, and 14% seed yield advantages over Vitabor, Australian lupin, and Probor variety, respectively. The seed yield performance of lupin varieties was positively correlated with the number of pods per plant while it was negatively correlated with the number of seeds per pod. The dry matter yield and number of seeds per pod were also significantly (P<0.05) affected by seeding rates of lupin varieties. The dry matter yield of lupin varieties increased with increasing seeding rates indicating the tested lupin varieties had a low tillering performance. The number of seeds per pod of lupin varieties decreased with increasing seeding rates. On the other hand, the nutritive values did not differ significantly (P>0.05) among the tested lupin varieties. However, Vitabor variety gave better CP and IVDMD followed by Australian lupin while Probor variety gave the lowest CP and IVDMD. Vitabor variety which exhibited better ash, CP, and IVDMD contents produced the lowest NDF, ADF, and ADL contents when compared with other varieties. Generally, Sanabor and Probor varieties had better forage dry matter yield and seed yield but Vitabor and Australian lupin had relatively better nutritive values. For forage production, lupin varieties should be sown with the highest seeding rate (100 kg/ha) while the lowest seeding rate (60 kg/ha) is recommended for seed production. However, this research should be done across locations and over years to prove the above-recommended seeding rates for forage and seed productions in the study area and similar agro-ecologies. Keywords: dry matter yield, herbage quality, plant height, pod number, seed yield, seeding rate.