ANNUAL REPORT, 1942 25 



followed an entirely different pattern. As the concentration increased, the sorp- 

 tion followed a smooth curve until 12.3 milli-equivalents per gram were sorbed 

 from a solution containing 40.0 milli-equivalents. As the concentration increased 

 above this point, there was a marked decrease in the sorption of the arsenate 

 and also a considerable increase in the volume of Kaolin (from 1.7 ml. to 5.0 ml. 

 per gram). The amount of arsenate sorbed remamed constant at 10.8 milli- 

 equivalents per gram between the concentrations of 40 and 50 milli-equivalents 

 per 10 ml. of solution and then increased rapidly in a true adsorption pattern up 

 to 24.1 milli-equivalents for a solution containing 80 milli-equivalents of arsenate 

 ion. It seems likely that both arsenate and water are sorbed by the Kaolin and 

 at the critical concentration of 40 to 50 milli-equivalents per gram, the water Is 

 sorbed more, thus causing the tremendous increase in volume of clay and making 

 it appear as though arsenate were not being adsorbed when one uses the solution 

 concentration as an index of the sorption. 



The same type of experiment was made with phosphate solutions and a typical 

 adsorption curve was obtained for this ion. No apparent increase in volume was 

 noticed at any concentration of phosphate and the maximum sorption was found 

 to be about 12.4 milli-equivalents of phosphate per gram of Kaolin. This ion 

 apparently does not have the marked hydrating effect exhibited by the arsenate 

 ion, although it is sorbed in considerable quantity. 



The Effect of Orchard Mulches on the Plant Nutrient Elements in the Soil. 



(Dale H. Sieling and J. K. Shaw.) Three test plots were established in the sum- 

 mer of 1941 to determine whether mulching with hay and glass wool had any 

 effect on the mobilization of the plant nutrient elements of orchard soils. One 

 plot received a two-inch mulch of Fiberglass wool, the second received a liberal 

 application of meadow hay, and the third was surface-cultivated to prevent the 

 growth of weeds. One year after the initiation of the experiment soil samples 

 were obtained from four depths in each of the test plots and analyzed for ex- 

 changeable bases and available phosphorus. No material change had taken 

 place in the plant food content of the soils at any depth after one year of the 

 treatments. These results were to be expected since there had been very little 

 decomposition of the hay mulch. More hay has been added to the plots which 

 are to receive hay mulch and samples wall be taken for analysis from all of the 

 plots again next year. 



CONTROL SERVICES 

 P. H. Smith in Charge 



The fertilizer, feed, seed, and dairy laws are administered as one service and 

 the operations of each of these, with the exception of the dairy law, are completely 

 reported in annual bulletins issued for that purpose. 



Besides the regular control activities the laboratory, through its staff, coop- 

 erates liberally' on numerous research projects active in other departments and 

 also performs many analytical and testing services for State institutions and for 

 private citizens who, because of the nature of their problems, deserve this con- 

 sideration. 



Under the dairy law 5,984 pieces of Babcock glassware were tested and 107 

 Certificates of Proficiency were issued during the year ending December 1, 1942. 



The enlarged emphasis on the vitamin values of all feeds, and commercial 

 feeds in particular, and the increased interest in the manganese content of poultry 

 mashes and in the protein quality of meat and fish products used for feed demands 



