122 EXPERIMENT STATION RECOED. 



soil mulches of different depths, cultivation to different depths, and shallow 

 and deep furrow irrigation. 



The results show that a dry granular soil mulch 3 in. deep reduced the loss 

 by evaporation from the soil at least one-half, a mulch 6 in. deep saved 75 

 per cent of the evaporation, and a 9-in. mulch was still more effective in 

 reducing evaporation, but was too expensive to be of practical value. The 

 effect of cultivation in lessening evaporation was especially marked in case of 

 the heavier soils. " There is a tendency in light sandy soils for the unculti- 

 vated surfaces to mulch themselves, and after the first few days following the 

 irrigation the losses diminish very rapidly, and in the end little advantage is 

 shown in favor of cultivation." 



The loss of water decreased with the depth of application. " Practical con- 

 siderations, however, limit the depth. Under conditions such as exist through- 

 out the arid, region this practical limit lies, it is believed, somewhere between 

 6 and 9 in. . . . In general, it may be stated that wherever the soil and the 

 crop will permit the water should be applied in deep furrows rather than by 

 flooding; that one deep, heavy irrigation is preferable to numerous lighter 

 irrigations, providing the crop is deep-rooted ; that cultivation should be prac- 

 ticed as early as possible after irrigation ; and that deep and frequent cultiva- 

 tion prevents evaporation and aerates the soil." 



Effect of heat and oxidation on the phosphorus of the soil, P. P. Peterson 

 {Wisconsin Sta. Research Bui. 19, pp. 16). — The author briefly reviews pre- 

 vious investigations on the subject, and reports the results of studies of the 

 effect of heat and of oxidation with hydrogen peroxid on the solubility of phos- 

 phoric acid of the soil and of wavellite and dufrenite. 



Heating wavellite for 5 hours to 200° increased the solubility of the phos- 

 phoric acid from 4 to 50 per cent, and heating it to 240° increased the solubility 

 to 100 per cent. Dufrenite, when heated to 200°, was but slightly increased in 

 solubility. 



The increase in solubility of the phosphoric acid of the soil was small at 130" 

 and rose rapidly with a rise in temperature above this point, reaching a maxi- 

 mum at 200°. The solubility of the phosphoric acid in clay and clay loam soils 

 was increased on an average about 50 per cent by decomposing the organic 

 matter with hydrogen peroxid. For sandy soils the increase was about oO per 

 cent. The increase in solubility by treating with hydrogen peroxid was always 

 larger than that due to heating, and there was no increase in solubility by heat- 

 ing after treatment with hydrogen peroxid. The phosphoric acid rendered 

 soluble by heating was from the same source as that obtained from oxidation 

 with hydrogen peroxid. The solubility of the mineral phosphates of the soil 

 did not seem to be increased by heating to 240°. The increase in solubility was 

 greater in the early than in the later stages of oxidation, being greatest when 

 from 25 to 30 per cent of the organic matter had been decomposed and ceasing 

 with GO per cent. 



The solubility of calcium and manganese was not increased by oxidation, 

 that of iron and aluminum was increased, the increase following pretty closely 

 that in the solubility of phosphoric acid. " The increased solubility of phos- 

 phorus by oxidation with hydrogen peroxid probably comes, in large part, from 

 precipitated iron and aluminum phosjjhates, held from solution before the oxi- 

 dation as part of a complex of insoluble organic matter and compounds of iron 

 and aluminum. Oxidation increases the solubility of the phosphorus but 

 slightly in subsoils. Heating after oxidation has a moi-e marked effect on the 

 solubility of the phosphorus in the subsoil than it has in the surface soil." 



Methods of determining' the intensity of respiration of bacteria in the 

 soil, J. Stoklasa (Ztschr. Landw. Versuchsiv. Osterr., IJf {1911), No. 11, pp. 



