The Influence of Seed Inoculation upon the Growth of Black Locust Seedlings 1

T ability of black locust (Robinia pseudoacacia) to utilize atmospheric nitrogen, together with its spreading root system, makes it .particularly adapted for soil conservation work. Mattoon (5) 3 reported that it is found widely distributed over the eastern half of the United States, but that its native home was probably in the Appalachian Mountains, including the outlying Piedmont region. He described it it as growing best on well-drained, neutral soils, and stated that it has been recommended for planting from the New England states south to Georgia and west to Texas, Missouri, and Illinois. The important symbiotic relationship between the black locust and the legume foot,nodule bacteria has been pointed out by a number of investigators. Nobbe, et al. (7) found that well-nodulated black locust seedlings produced a better vegetative growth than similar plants without nodules but which received either ammonium sulfate or calcium nitrate fertilizer. Mattoon (5) concluded that the presence of rhizobia in the roots of the locust seemed to give it a greater resistance toward attack by the locust borer. McIntyre and Jeffries (6) found that nodulated black locust trees increased the nitrogen content of the soil and made" it more productive. They reported that the growth rate of catalpa and the amount of nitrogen in the soil decreased as the distance from the adjacent black locust plantings increased. Some investigators in working with black locust have failed to take advantage of this symbiotic relationship. Ware (~o), in a recent bulletin, reported that the locust grew but very poorly in the depleted soils of Alabama unless it received a complete fertilizer. He advocated about 0.4 pound per plant of a 2-8-4 fertilizer supplemented with about o. ~ pound of nitrate of soda. Accordingly it was concluded that the cost of establishing the locust satisfactorily makes it too costly to use in ]arge scale reforestation programs, or for largescale plantings on abandoned agricultural land. Throughout" the report, however, no mention was made of the use of any bacterial inoculant for the plants. It appears reasonable that proper inoculation of the seed might make the use of much of the expensive fertilizer materials unnecessary and also insure a more vigorous continued growth of t,he plants. Many experiments have been conducted which have shown the advantage of seed inoculation in the growing of the common legttmes. No papers are available, however, which report a similar study of the