BUREAU OF PLANT INDUSTRY. 165 



carriers. Field experiments have been conducted on the Washburn 

 and Caribou silt loam in Maine; on the Sassafras silt loam on Long 

 Island and in New Jersey ; on the Penn loam in New Jersey ; on the 

 Hagerstown loam in Pennsylvania ; on the Norfolk fine sandy loam in 

 Virginia, North Carolina, South Carolina, and Florida; on the Nor- 

 folk sandy loam in Florida and the Norfolk coarse sandy loam in 

 South Carolina; on the Portsmouth sandy loam in South Carolina; 

 on the Coxville fine sandy loam in South Carolina ; on the Orange- 

 burg sandy loam in Georgia; on the Pope fine sandy loam in Arkan- 

 sas; on the Greenville sandy loam in Georgia; on the Susquehanna 

 fine sandy loam in Georgia; on the Scottsburg sandy loam in In- 

 diana; and on the Superior silty clay loam at Ashland, Wis. 



In the plan of experimentation followed there are being deter- 

 mined the best ratios of the plant-food constituents in the fertilizer 

 mixture suited to the respective soils, the amount of these fertilizers 

 giving the most profitable returns, and the availability of the various 

 carriers for phosphate, potash, and nitrogen in the fertilizing mate- 

 rials commonly employed, as well as those which have been intro- 

 duced during the war. 



The American sources of potash studied are the salts from the 

 Nebraska lakes, which are principally carbonates ; the salts from the 

 California borax lakes, which are principally muriates; the product 

 from alunite mined in Utah, which is a high-grade sulphate of 

 potash; ground kelp from the Pacific coast, tobacco stems, beetr 

 waste potash, and several potash materials collected as dust from 

 the cement mills. The sources of nitrogen studied are sodium ni- 

 trate, ammonium sulphate, dried blood, cottonseed meal, and cyana- 

 mid, a nitrogen-fixation product now used in fertilizers. The ex- 

 periments are showing that these different materials have different 

 economic importance, depending upon the soil and crop. 



The crops grown in these fertilizer tests are those of greatest in- 

 terest or economic importance to the region studied and include po- 

 tatoes, cotton, corn, citrus fruits, pecans, sorghum, clover, celery, etc. 

 These experiments are carried on cooperatively with the State agri- 

 cultural experiment stations and other local associations and also 

 with various offices of the department. The results obtained are be- 

 ing collected for a comprehensive study of these different soil types, 

 but they are already yielding valuable results for local application 

 as to the fertilizers best suited for particular regions and are also 

 furnishing information to the farmers as to the various nitrogen and 

 potash carriers most likely to produce the best returns in practice. 



STUDIES OF THE MALNUTRITION OF CROP PLANTS. 



The study of the malnutrition of certain plants, most notably of 

 potato and cotton, which became particularly emphasized during the 

 war, has been continued, and further facts regarding the distribu- 

 tion of these diseases and their relation to soil types, systems of agri- 

 cultural practice, and fertilizers used have been determined. New 

 and untried fertilizing materials are sometimes responsible for these 

 troubles, but more often they have been due to an unbalanced con- 

 dition in the fertilizers, due to too great an increase in one of the 

 ingredients, with often total elimination of another. This in some 

 regions has produced the so-called potash hunger of the potato plant, 



