The influence of seed inoculation upon the growth of black locust seedlings
1936
Thorne, D.W.
Experiments conducted in cooperation with the U. S. Dept. of Agriculture Soil Conservation Service and Forest Service nurseries in Iowa have shown the advantages of inoculation of black locust seeds. Although there was considerable nodulation of seedlings throughout the nurseries as a result of the presence of root-nodule bacteria in the soil, seedlings growing from the inoculated seed made better growth and fewer died during the summer months than did the seedlings which were infected only with the native microflora of the soil. The increase in total nitrogen content of the seedlings as a result of inoculation was 297.2% on a soil of low fertility and 80.4% on a soil of rather high fertility. The nodules formed from pure culture inoculation were more numerous and were generally located much nearer the tap root of the host plant and closer to the surface of the soil than the nodules induced by the rhizobia occurring in the soil. Two reasons for the beneficial results from inoculation were suggested, viz., (a) inoculation resulted in a greater number of nodules located nearer the tap root of the plant; and (b) the strain of organisms supplied in the pure culture inoculum was more efficient than the average of the strains of this species originally present in the soil. Cross inoculation tests showed that Rh. meliloti, Rh. trifolii, Rh. leguminosarum, Rh. phaseoli, Rh. japonicum from both soybeans and cowpeas, Rh. lupini, and the root-nodule bacteria of dalea (Wood's clover) were not capable of producing nodules on black locust roots. Furthermore, the black locust root-nodule bacteria were not capable of producing nodules on the leguminous symbionts of the above species of bacteria.
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