120 EXPERIMENT STATION RECORD. 



The yield of grain was found to increase with increased loam addition. Fer- 

 tilization with a mixture of phosphoric acid and potash further increased the 

 yield, and somewhat more than fertilization with phosphoric acid alone, but 

 with increasing loam treatment the difference in yields brought about by the 

 two fertilizers steadily decreased. When practically the same experiments were 

 made using sand instead of loam, the same general results were obtained ex- 

 cept that the yields of grain were not nearly so large. The addition of lime 

 showed little or no beneficial effect except where iron sulphid was present in the 

 loam. 



Comparative tests of lime and loam treatment of peat soils favored the loam, 

 although the crop yield increased as the application of lime increased up to 

 2,670 lbs. per acre. It was found that repeated burning in case of certain peat 

 swamps so reduced the nitrogen content that the crop yield was considerably 

 lowered, making the addition of nitrogenous matter necessary. 



The heat conductivity of damp sand and loam was found to be three or four 

 times that of the peat. It was also found that loam treatment of peat soils suffi- 

 ciently arrested frost action to allow plant life to exist in much colder weather. 

 This is attributed to the better physical condition of the soil. 



Moor culture, A. Kostlan (Jahresher. Landiv., 27 {1912), pp. 200-215, fig, 

 1). — Reports of recent investigations on this subject are classified and reviewed. 



The shrinking of swamp soils resulting" from drainage and cultivation, 

 B. Tacke {Jalir'b. Moork., 1 {1912), pp. 35^5, pi. 1). — Attention is called to the 

 marked shrinking and sinking of swamp soils resulting from drainage and 

 other improvements. A sinking of from 15 to 25 per cent of the soil depth has 

 been found to take place within 15 years after drainage in many swamps, 

 especially in those from which the peat has been stripped. The shrinking and 

 sinking occur in layers and not as a solid mass. 



The degree to which drainage so affects the soil is said to depend chiefly on 

 the physical and chemical composition and depth of the soil, on the amount 

 and depth of drainage, and on the character and condition of the subsoil. In 

 some upland swamps which are drained and stripped of peat the bed soil sinks 

 below the water level in the drainage ditches. To obviate this it is suggested 

 that in stripping the peat a bed be left somewhat more than 50 cm. above mean 

 water level in the ditches and this be mixed with sand to reduce the shrinkage. 

 Cultivation of peat stripped soil reduces the shrinkage more than the sand 

 treatment, but the productivity is said to be not nearly so great. The effect 

 of drainage on such soils can best be determined by observing the relative 

 movements of the layers and comparing their densities as determined before 

 and at intervals after drainage. 



Investigations on the influence of plant roots on the structure of the soil, 

 M. Berkmann {Internat. Mitt. Bodenlc, 3 {1913), No. 1, pp. 1-Jf9, figs. 6). — ^A 

 series of pot experiments with two representatives soils, one a sandy soil con- 

 taining considerable humus and little clay and the other a clay loam soil, were 

 conducted over a period of two years to determine the influence of plant roots 

 on the soil structure and also the effect of physical changes within the soil 

 itself. The soils were prepared by tamping some and puddling others into 

 place, and still others were experimented with in a loose mellow condition. 

 Plants representative of the two general types of rooting were grown on some 

 of the soils while others were left bare. 



It was found that different kinds of soils, especially those rich in clay, are 

 loosened not only by absorbing water but also as a result of the eff'ect of frost, 

 variations in moisture content, etc. In loose soils a very small percentage of 

 the spaces is filled by the stronger tap roots so that there is no essential de- 

 crease in the original mellowness from this source. In compact soils roots may 



