1917] SOILS FERTILIZEES. 319 



9 (1917), No. 7, pp. 18S-252, figs. i9).— Experiments conducted in cooperation 

 ^Yitll the California Citrus Substation at Riverside are reported. 



It was found that " semiarid soils frequently fail to nitrify dried blood when 

 added in 1 per cent quantities, but invariably nitrify blood when added in 

 amounts not greatei" than are ordinarily applied under the field conditions. 

 The addition of dried blood to semiarid soils in 1 per cent quantities frequently 

 caused large amounts of ammonia to accumulate in the soil. The addition of 

 dried blood or other nitrogenous substances applied as fertilizers caused no 

 marked increase in the ammonia content of the soils. When 1 per cent of dried 

 blood is added to semiarid soils, as much as 50 per cent of the nitrogen added 

 may be lost during an incubation period of six weeks. As the soils frequently 

 give off a strong ammoniacal odor, it is believed that this loss is due, in a large 

 measure at least, to the volatilization of ammonia. Ammonification or nitrifica- 

 tion studies on semiarid .soils in which 1 per cent of dried blood is added are of 

 questionable value and may lead to erroneous conclusions. 



" Green manures, especially the legume varieties, nitrify very rapidly. As 

 much as 50 per cent of the nitrogen contained in green plant tissues may be 

 converted into nitrates in 30 days. Green manures furnish a valuable source 

 of energy for the nonsymbiotic nitrogen-fixing organisms. 



" The furrow system of irrigation frequently causes a very unsatisfactory 

 distribution of the soil nitrates. In many citrus groves more than two-thirds 

 of the nitric nitrogen in the upper 4 ft. of soil is found in the surface 6 in., in 

 which, because of the frequent cultivation, few feeding roots are found. The 

 furrow system of irrigation frequently causes the formation of niter spots. 

 Surface scrapings from these spots in heavily fertilized groves may contain 

 as much as 1 per cent of nitrogen as nitrates. The brown color which charac- 

 terizes the niter spots is probably due to a number of factors, but it is 

 believed that the deliquescent character of the calcium nitrate is important 

 in this regard. Where the furrow system of irrigation is employed, the 

 fertilizing materials should be plowed down somewhat deeper than the land 

 is cultivated. The feeding roots will then have an opportunity to assimilate 

 the food as it is rendered available, whereas, if it is formed within the culti- 

 vated zone, the irrigation will tend to carry it farther away from the roots. 



" Much nitric nitrogen is lost from citrus lands by leaching. The most 

 effective means of preventing this loss is by growing a winter cover crop. 



" Basin irrigation or overhead irrigation gives a more satisfactory distribu- 

 tion of soil nitrates than the furrow system. The basin system of irrigation 

 seems to give greatest promise when combined with a mulching system. How- 

 ever, the rapidity with which organic materials rich in nitrogen decay would 

 seem to make it inadvisable to maintain a constant mulch with these materials, 

 as the nitrates produced will probably be far in excess of the needs of the tree, 

 and much loss will result." 



Conclusions as to mottle-leaf are noted on page — . 



Fourteen references to literature bearing on the subject are appended. 



Tests on the disinfection of soil, Mr&CE (Conipi. Rend. Acad. Sci. [Paj'is], 

 164 (1917), No. 9, pp. S62-S65). — Two series of experiments on field, garden, and 

 greenhouse soils with potatoes, buckwheat, tomatoes, kidney beans, carrots, 

 leeks, cucumbers, and carnations are reported. The materials used were 

 toluene, carbon bisulphid, lysol, potassium permanganate, copper sulphate, 

 formalin, sulphur, calcium hypochlorite, charcoal, and oxygenated water. 



It was found that treatment of the soil with these substances had a favorable 

 influence on the different vegetables on different soils. This favorable influence 

 was found to be specific with reference to the chemical substance used for cer- 



