516 EXPERIMENT STATION RECORD. 



The economical maintenance and development of soil fertility, C. E. 

 Thokne {liicii. Rpt. Tonn. Dept. Agr., 1900-10, pp. 28-',-S00) .—This article de- 

 scribes the system of rotation, the use of manure reenforced with ground rock 

 phosphate, growth of clover, and application of lime and commercial fertilizers 

 followed at the Ohio Experiment Station in increasing the productiveness of 

 tlie soil. 



The development of the use of manures and fertilizers, P. Schack {Ver- 

 handl. Naturw. Vcr. Hainhurf/, 3. scr., 17 (l<J0D),pp. LXV-LXV 1 1). —The author 

 concisely reviews the develoiiment of the use of manures and fertilizers from the 

 earliest ages to the present time, and in conclusion points out that the object 

 sought in the use of fertilizers, according to Liebig's theory, should be to find 

 the optimum amount of fertilizer to use with each soil and to avoid the use of 

 anything more than this. 



Stable manure and green manuring, Schneidewind (Ber. Landw. Reich- 

 samtc Imiern [Germany^, 1910, No. 17, pp. 69-77). — This article, based upon 

 experiments at Halle, deals with the composition, deterioration, and preserva- 

 tion of manure, and the effect of stable manure and of green manures on differ- 

 ent crops. 



The results indicate that the most profitable returns can be obtained in the 

 case of root crops only by the use of manure with commercial fertilizers. 

 About 25 per cent of the nitrogen of the manure was found to be utilized in 

 the course of two years. It was thought that the beneficial effect of the 

 manure was due to a considerable extent to the potash and phosphoric acid 

 which it contained. 



Green manures were found to give best results on light soils poor in humus 

 and nitrogen. The crops which appeared to be best suited to culture with 

 green manures were beets, potatoes, and oats. The sugar content of beets 

 was slightly depressed by green manures, but to a less extent than by stable 

 manure. The effect of the green manures on potatoes was very variable, but 

 they were less beneficial than stable manure. The beneficial effect of the green 

 manures was increased by thorough cultivation. Oats made a most decided 

 response to green manures. 



The Halle experiments indicate that green manures should not be plowed 

 under deeper than 25 cm. (about 9.S5 in.). On light soils they should be 

 plowed under in late fall, winter, or early s]iring, while on better soils they give 

 best results when plowed under before frost in the fall. In the case of light 

 soils early plowing under is likely to result in loss of nitrogen. It was found 

 profitable to use a small amount of nitrate of soda in addition to green manure 

 on light soils, and on all soils a basal fertilizer containing potash and phos- 

 phoric acid is recommended. 



The deterioration of manures under semiarid conditions, W. P. Headden 

 and E. Douglass {Colorado Sta. Bui, 168, pp. 32). — This bulletin is based upon 

 examiuations of a large number of samples of sheep and cattle manure of 

 various ages and kept under different conditions of moisture and exposure. 



The main facts brought out in the bulletin ai-e that manure under arid con- 

 ditions does not lose weight as rapidly as in more humid regions. Sheep ma- 

 nure lost 32.5 per cent in weight in about 15 months and 56.7 per cent in a little 

 over 2 years. Such manure normally contains about 13 per cent less moisture 

 than in moist climates. 



The phosphoric acid decreased 42 per cent in 15 months and 59 per cent 

 in 2 years, the loss in phosphoric acid agreeing quite well with the loss in 

 weight. 



Manures in semiarid regions differ most decidedly from those of humid 

 climates in percentage of potash. Probably as a result of the light rainfall, 



