Scientific Agriculture. 



374 



[June 1907. 



ill a pamphlet entitled " Soil inoculation for legumes" (Bureau of Plant Industry, 

 Bulletin No. 71). In the course of these investigations many very interesting facts 

 have been brought to light and the conclusions arrived at are of great importance. 

 The most interesting information to the practical agriculturist, however, is that 

 dealing with the inoculation of the soil and the effect produced upon the crops 

 grown. The materials necessary for inoculatioii as originally issued by the United 

 States Department of Agriculture consisted of three small packages, one of which 

 contained a mixture of sugar, magnesium sulphate and potassium phosphate, another 

 contained some ammonium phosphate and the third a pad of cotton wool which had 

 been soaked in a pure culture of the organism and afterwards carefully dried. In 

 this state the organism retains its activity for some months, while if kept in nutrient 

 agar, it looses its activity in a few weeks. It has, however, been found that the 

 dried cultures on cotton are not wholly satisfactory, and further investigations on the 

 subject have resulted in a modification in which the pure cultures of the organism 

 are issued in hermatically sealed tubes. Full particulars of the new method are 

 given in Parmer's Bulletin No. 240, " Inoculation of Legumes," 1905, published by the 

 Department of Agriculture, U.S.A. 



The method of inoculation is as follows. The contents of the first package 

 are dissolved in a certain quantity of clean water and in this nutrient solution is 

 placed the bacterial preparation. The liquid is allowed to stand in a Avarm place for 

 twenty-four hours, being protected as far as possible from dust and the ammonium 

 phosphate is then added whereby a further growth of bacteria is induced. After 

 standing for another twenty-four hours the solution becomes cloudy from the 

 growth of the bacteria, and is then ready for immediate use. 



Either the seed or the soil itself may be inoculated. In the former case 

 inoculation is effected by thoroughly moistening the seed with the liquid and then 

 drying it in the shade ; the seed may then be kept for several weeks before sowing 

 without deterioration. Inoculation of the soil is carried out by moistening some 

 dry soil with the liquid, thoroughly mixing this with a further quantity of soil, and 

 then distributing it over the field- In order to test the efficiency of these methods 

 of inoculation, 12,490 packages of material were distributed free by the United 

 States Department of Agriculture between November 1902 and November 1904. In 

 this way some 12,500 tests were obtained in almost all parts of the United States and 

 in many other countries also- Out of 2,502 tests with various leguminous plants only 

 26 per cent, of failures were recorded, and many of the latter were due to the experi- 

 ments having been made in places which were obviously unsuitable for the method 

 of treatment. 



The following conclusions may be drawn from the results of these 

 experiments. Inoculation is not likely to produce any beneficial effect upon soils 

 which already contain the necessary bacteria or upon soils rich in nitrogen, or again 

 upon soils which on account of their acidity are unsuitable for the growth of legu- 

 minous plants. Inoculation is undoubtedly of value where the bacteria do not 

 already exist in the soil, or have lost their activity, as indicated by failure in the 

 growth of leguminous crops and absence of root nodules. 



Experiments have also been carried out by the United States Department of 

 Agriculture with such leguminous plants as are suited to the climate and 

 and soil of the districts in which Experiment Stations exist, with a view to dis- 

 covering their value as green manures and as fodder. The conclusions arrived at 

 from the results of these experiments have been published in a bulletin (Farmer's 

 Bulletin No. 16), and the fertilising value of some of the plants tested is shown in the 

 (following table i— 



