2 FERTILIZING VALUE OF HAIRY YETCH. 



IMPORTANCE OF INOCULATING HAIRY VETCH. 



If hairy vetch was to prove at all valuable as a fertilizer, it was nee- 

 essary to get the crop w^ell inoculated. Plat experiments in collabora- 

 tion with Mr. Shamel were therefore undertaken in the autumn of 

 1906 at Hockanum, Conn., by the Ofl&ce of Soil Bacteriology Inves- 

 tigations to determine, if possible, the value of hairy vetch as a fertili- 

 zer on the soil of that region. Tobacco following uninoculated vetch 

 has shown but little advantage over that following a rye cover crop, but 

 where hairy vetch has been inoculated and an abundance of root 

 nodules have resulted the tobacco following has been greatly benefited 

 both as to yield and as to qualit3\ When one compares the growth of 

 inoculated and uninoculated vetch this will be easily understood. 



The yield of hairy vetch in 1907 at Hockanum, Conn., as found 

 from sample cuttings on 1 square rod of our test plats, amounted to 7 

 tons 400 pounds an acre (green weight) for the inoculated vetch and 2 

 tons 240 pounds an acre for the uninoculated vetch. Rye on this land 

 made a vigorous growth, yielding at the rate of 7 tons 720 pounds an 

 acre. 



To determine further w^hether the difference in yield in this test could 

 be due to any difference in soil nitrogen, determinations of total nitro- 

 gen in samples of the soil were made by the Bureau of Chemistry. It 

 was found that the soil where vetch was growing without inoculation 

 contained 0.19 per cent of total nitrogen, or more than that found on 

 either the plats of rye (0.17 per cent) or inoculated vetch (0.14 per 

 cent). Yet with this greater source of nitrogen in the soil the vetch 

 lacking nodules made less than one-third the growth attained where 

 the plants were properly inoculated. It may be said that in one case 

 nodules were absolutely lacking, while in the other the nodules were 

 so abundant that when the vetch was plowed under the upturned soil 

 was dotted white with the glistening nodules. 



POT EXPERIMENTS WITH HAIRY VETCH. 



To check under controlled conditions the results obtained in the tests 

 at Hockanum, Conn., a quantity of soil from the uninoculated plat was 

 shipped to Washington and some experiments were undertaken in the 

 greenhouse. This soil was placed in large pots (holding about 30 

 pounds of soil each) and planted with seed of hairy vetch, ten plants 

 to a pot. One-half of the pots were sown with seed treated with a pure 

 culture of the vetch-nodule organism, the remainder being untreated. 

 The pots were watered throughout with water sterilized by boiling. 

 Despite this precaution and a preliminary sterilizing of the pots and 

 seeds, a partial inoculation of the control plants took place — probably 

 due to insects traveling from the inoculated pots. This chance inocu- 

 lation occurred, however, too late to benefit the control plants as much 



