570 EXPERIMENT STATION RECORD. 



nitrifying organisms derive their carbon from carbon dioxid and not 

 from carbonates. To further test this matter 3 experiments were 

 instituted in Avhich solutions containing hke amounts of ammonium 

 sulphate and magnesium carbonate were inoculated with nitrifying 

 organisms. In 2 of the experiments the apparatus was filled with 

 air containing carbon dioxid ; in the other with pure air. In the first case 

 there was a reduction of volume which was not noticed in the latter 

 case. The magnesium carbonate was not utilized as a source of carbon. 

 In the presence of carbon dioxid the nitrifying organisms converted 

 almost all of the ammonia into nitrous acid, although no nitrates were 

 formed and a variable amount of the nitrogen was lost in the free state. 



Forestry-meteorological observations, E. Wollny {Forsch. Geb. 

 agr. Phys., 10 {1S96), No. 1-3, pp. 151-171). — These include studies of 

 the influence of plant cover on the carbon dioxid content of soil air, on 

 the organic and mineral constituents of the soil, and on the productive 

 capacity of the soil. Data for observations on the carbon dioxid con- 

 tent of the soil air, and on the carbon, humus, and nitrogen in the cases 

 of soils covered with pines (with and without cover of litter), with 

 birches, and with grass, and manured and unmauured plowed land are 

 tabulated. The yields on bare soils and on soils which had been covered 

 in previous years with several difierent kinds of plants are also given. 



The results show that soils covered with plants contained more car- 

 bon dioxid than bare soils, the conditions being otherwise the same. 

 This was not true of soil to whi(;h manure had been applied. In this case 

 the carbon dioxid content was much greater than in any other case. 

 There was a larger percentage of carbon dioxid in the air of the soil 

 covered with grass and with birches than in that bearing pines. In the 

 case of the pines the amount was greater where the soil was covered 

 with litter than where the litter had been removed. 



Soils covered with living plants contained considerably more carbon, 

 humus, and nitrogen than the bare soil, other conditions being the 

 same. Of the soils covered with vegetation, those in grass and pines 

 with a cover of litter contained more of these constituents than simi- 

 lar soils in birches and pines without litter. In the soils covered with 

 j)lants the increase of carbon was relatively higher than that of nitro- 

 gen. In 7| years there was a marked increase of these constituents in 

 soils covered with plants, and a decided loss of organic matter in bare 

 soils of similar character. 



Soils covered with vegetation contained a larger amount of mineral 

 matter soluble in hydrochloric acid than those remaining bare, the con- 

 ditions being otherwise the same. This difference was most marked in 

 the case of lime, the other constituents being affected to a much less 

 extent. The soils in grass and in pines with a cover of litter contained 

 a larger amount of mineral matter, especially of lime, than those in 

 pines without a cover of litter and in birches. 



The yield on soils which had previously been for a number of years 

 in forest was considerably greater than on those which had remained 



