'S7 



part colder than that free from stones, while during its maximum it is 

 warmer. In regard to conditions of moisture, field soil covered with stones 

 is found to be wetter during the warmer seasons than uncovered soil of 

 otherwise similar composition. Soil covered with stones lets more water 

 slip through than does one not so covered. 



The Use of Lime, Marl and Plaster. 



The importance of lime arises from its chemical action as a direct 

 nutritive substance as well as from its properties, which change the mechan- 

 ical constitution of the soil. Aside from favoring friability, it should be 

 emphasized that the lime attacks the silicate in clay soils and sets free sol- 

 uble potassium compounds. By its more rapid destruction of the organic 

 substances, it causes a better decomposition of humus. 



In regard to the technique in using lime, it is advisable to keep burnt 

 (quick) lime in baskets under water until no more air bubbles arise (possibly 

 3 to minutes) and then to heap up the pieces in layers. They decompose 

 (slake) of themselves and the lime stone, which lost its carbon dioxid in the 

 previous burning, now becomes the ^white powdery calcium hydroxid 

 (Ca(OH)^) and as such represents slaked lime, which is soluble in 730 

 parts of cold water, and only in 1300 parts of boiling water (lime water). 

 100 parts of quick lime correspond to 132 parts of slaked lime. The lime 

 should be uniformly spread over the field in quiet weather by hand, or with 

 a suitable shovel. It is well to spread it in the fall on the stubble and then 

 to work it under the surface. If it is necessary to wait until spring, it must 

 be spread as early as possible before seeding, as soon as the soil has dried. 

 Smaller doses (750 kg: to 1500 kg. per hectare) repeated about every five 

 years, are more advisable than a single heavy liming, because, in the latter, the 

 decomposition of the humus is so violent that the subsequent increase in the 

 harvest is at the cost of a later production. It is said in practice that fer- 

 tility is difficult to maintain on a lime-stone soil, because organic matter dis- 

 appears rapidly. 



Naturally the amount of lime depends upon the soil. Tough clay soil 

 will bear most, while great care must be used with poor sandy soil. Soils 

 which are lacking in organic matter or have water standing on them, may 

 not be limed at all. The results which become evident most quickly are 

 given by a humus soil poor in lime ; — Sorrel (Rumex acetosella) indicates 

 a scarcity of lime. Lime will act here splendidly as a fertilizer. 



If local lime deposits be used, such as possibly meadow-lime or marl, or 

 the so-called waste lime (gas lime, lime ooze, lime ash), it is distinctly ad- 

 visable, before using it, to let the air pass through in order to decom- 

 pose it, or still better, to let it freeze. When using waste lime one should 

 convince oneself first of all, by a simple experiment, that no injurious sec- 

 ondary action can take place. According to Hoffman's experiments^ it 



1 Mitteilungen der Deutsch. Landwirstchafts-Ges. 1905, p. 367. 



