224 REPORT OF OFFICE OF EXPERIMENT STATIONS. 



Progress was reported on all Adams fund projects, but in most 

 cases the work was only partially completed. The investigation of 

 the efficiency of rations fi*om single-plant sources in animal feeding 

 was continued. Previous work with cattle showed that an exclusive 

 wheat ration was apparently highly injurious, and a study to deter- 

 mine the cause of this effect was pursued with other types of farm 

 animals. 



The study of the mineral requirements of farm animals was 

 carried on as in previous j^ears. The normal grain feeds were found 

 to contain insufficient lime for the best development of growing ani- 

 mals, and the addition of floats, ground limestone, or finely ground 

 leguminous hay, such as alfalfa or clover, were especially helpful in 

 developing a strong skeleton. The experimental results further in- 

 dicated that mature swine, not fonning new muscular tissue, or 

 undergoing such physiological processes as milk secretion and re- 

 l^roduction, can be maintained in a normal condition on a low lime 

 supply. Magnesium salts directly injected into the blood of swine, 

 or added with the food as sulphates or chlorids, produced an in- 

 creased excretion of calcium in the urine. "\Mien feeds containing a 

 large amount of magnesium as compared to their content of calcium 

 were used, this increased calcium excretion did not occur. 



The soils department in the study of conditions affecting the avail- 

 ability of untreated rock phosphate, used as a fertilizer, found that 

 when this substance and manure are composted, the solvent action of 

 the organic matter on the phosphate is slight. When the carbon 

 dioxid produced by the composting of the manure was brought into 

 direct contact with rock phosphate held in suspension in water, the 

 solvent action was much greater. It was further found that the 

 process of solution in either of these conditions soon reaches an 

 equilibrium and no further solution takes place. It is concluded 

 that the availability of rock phosphates to plants can not be deter- 

 mined by its solubility in acid solvents, such as a 0.2 per cent citric 

 acid. In a siudy of the relation of bacteria to the solubility of rook 

 phosphate in fermenting manures, a reduction in the amount of 

 soluble phosphorus avj»s noted and found to be directly associated 

 with bacterial cell development. An investigation of oxidation and 

 heat in their relation to the solubility of soil phosphorus showed 

 that 80 to 90 per cent of the organic matter can be removed from a 

 soil by oxidation with hj^drogen peroxid. After the destruction of 

 this amount of organic matter, the increase in the solubility of the 

 phosphorus in fifth nonnal nitric acid was 30 to 50 per cent of the 

 total phosphorus. Heat did not increase the solubility so much and 

 did not increase it at all after the action of hydrogen peroxid. In 

 this connection, attention was also given to the solubility of iron, 

 aluminum, calcium, and manganese. 



