Effect of combined inoculation strains on growth of lupin on newly reclaimed land in Egypt

Abstract

Inoculation studies with Bradyrhizobium isolates were investigated in a glasshouse and field experiment to compare the effects of single and multiple rhizobium inoculations on growth and symbiotic performance in lupin cultivation. A clear difference in host–strain compatibility was observed 120 days after sowing (greater number and dry weight of nodules, higher shoot dry weight and total N accumulation). To confirm the results from the glasshouse, combined inoculations with a different level of N fertilizer and six lupin cultivars were tested on newly reclaimed land at Tahreer Governorate, Egypt. N fertilizer application significantly decreased nodulation status of white lupin, but increased seed and straw yields compared with the non-fertilized control. Two combined inoculations were superior to the other strains in terms of infection and development of nodules in four accessions (1, 20, 30 and 32) and the cultivar Giza 1. All combinations of rhizobium strains tested enhanced the growth and total N accumulation of the lupin cultivars. Rhizobium inoculation increased seed and straw yield compared with the non-inoculated control. Reactions of the tested strain inoculations and interaction between Rhizobium strains and host plant in the glasshouse were almost identical to their reaction in the field. The results from this study suggest that the improvement through development of combined inoculation strains could be possible and would offer security for nodulation. High yields were accomplished with seed inoculation, particularly when lupin was cultivated for the first time and indigenous populations of rhizobia in the soil were low.