The effects of inoculation and N fertilization on soybean [Glycine max (L.) Merrill] seed yield and protein concentration under drought stress

  1. Basal, A. Szabó

 

Institute of Crop Sciences, Faculty of Agricultural and Food Sciences and Environmental management, Böszörményi út 138, Debrecen, Hungary

 

DOI: 10.15547/ast.2018.03.044

(Manuscript received 7 June 2018; accepted for publication 8 August 2018)

 

Abstract. An experiment was conducted during 2017 growing season in Debrecen, Hungary to investigate the effects of inoculation and N fertilization on the seed yield and protein concentration of soybean [Glycine max (L.) Merr.] cultivar (Boglár) under three irrigation regimes: severe drought (SD), moderate drought (MD) and control with no drought stress (ND). Three N fertilizer rates were applied: no N (0N), 35 kg/ha (35N) and 105 kg/ha of N fertilizer (105N). Half of the seeds in each treatment were inoculated with Bradyrhizobium japonicum inoculant. The results showed significant differences in the seed yield associated with both inoculation and irrigation, whereas there were no significant differences in the seed yield associated with fertilization. When seeds were inoculated, yield was increased when (35N) was applied compared to (0N); however, high rate (105N) reduced the yield to a level even less than (0N). When seeds were not inoculated, the highest rate of N increased the yield the most compared to the other two N fertilizer rates under drought. Under severe drought, inoculation was positively and significantly correlated with yield; however, adding N fertilizer increased the yield of non-inoculated plants compared to the inoculated ones, regardless of N-fertilizer rate. Protein concentration in the seeds was significantly affected by irrigation and by fertilization, but not by inoculation. Protein concentration increased as N fertilization rate increased, regardless of inoculation or irrigation; moreover, increasing N rate reduced the correlation coefficient of protein concentration with irrigation. It was concluded that adding N-fertilizer is not always recommended, especially when seeds are inoculated before being sown; however, it is very important under severe drought stress to sustain yield. Enhanced protein concentrations could be achieved by applying N fertilization, whether the seeds were pre-inoculated or not.