No. 6. DEPARTMENT OF AGRICULTURE. 215 



should not give a good inoculation, that is, if used within two or 

 three months after treatment. 



In regard to the proper method of handling soil-inoculating cul- 

 tures very little need be said; the directions are quite simple. The 

 dried cotton culture is usually wrapped in tinfoil and, after open- 

 ing, is placed in a solution formed by adding the contents of package 

 "No 1" to a definite quantity of clean water. This solution contains 

 one per cent, of sugar 1-10 per cent, of potassium phosphate, and 1-100 

 per cent, of magnesium sulphate. These salts with the sugar as a 

 source of energy, favor the growth of the nitrogen-fixing bacteria 

 held dormant in the cotton but do not offer a good medium for the 

 growth of yeasts and molds carried about in the air and which are 

 bound to contaminate the culture in a greater or less degree. This 

 contamination should be reduced as much as possible by previously 

 boiling the water and allowing it to pool, at loast until lukewarm 

 scalding out the bucket or tub, and keeping the liquid covered at all 

 times. The temperature maintained should be that of an ordinary 

 living room; about 70 degrees Fahrenheit. After twenty-four hours- 

 growth in this solution, another package is added, containing ammo- 

 nium phosphate in amount equal to one-half per cent, of the total 

 solution. This causes a rapid division or growth of the bacteria 

 so that during the next twenty-four hours, with all conditions 

 favorable, the liquid will become so filled with the organisms that 

 it will appear slightly milky or cloudy. It is then r'eady to apply 

 to seed or to be mixed with soil, either method being effective for 

 carrying the bacteria into the soil. One gallon will moisten at 

 least two bushels of seed which should then be spread out to dry 

 but not so as to receive the direct sunlight; if mixed with soil for 

 top dressing the same amount, one gallon, will impregnate sufficient 

 soil to spread over four acres (or less). By hand-sowing, a wagon 

 load will be sufficient for this area. 



The successful issue of last season's experiments brought about 

 a demand for the cultures which the Department of Agriculture 

 could not have anticipated, nor is it probable that our laboratories 

 could have met the demand in any case. Early in February we 

 found that we had already liste.d as many applicants as we could 

 accommodate up to July 1st and since that time we have been unable 

 to furnish cultures except in cases where, for special reasons, a 

 test appeared necessary. This fall and next spring, however, the 

 distribution will be continued as far as our limited facilities permit, 

 but our lists will not be made up more than two months previous 

 to seeding time. 



Naturally we have had a great many inquiries in regard to the 

 quality of the cultures obtainable from commercial sources. We can 

 only say that the bacteriologists for such concerns have been given 



