SOILS AND FERTILIZERS 371 



Moreover, the great weight of such a plow is extremely beneficial to 

 pack the soil so as to secure a firmer seed bed. This compacting of 

 the peaty soil doubtless hastens its rotting and the necessary chemical 

 decomposition to produce fertility, while it also firms the soil, thus 

 greatly improving its texture as a seed bed, especially for cereals. 

 These crops ordinarily do best on rather close soil, such as clay or 

 clay loam, and the more nearly marsh soils can be brought into that 

 condition the better will they be adapted to their culture. 



In chemical composition, marsh lands differ from upland soils 

 chiefly in having a very large amount of nitrogen, due to their high 

 content of organic matter and usually a relatively smaller amount 

 of the other essential plant food elements, phosphorus and potassium. 

 When marsh soils occur in a limestone region, such as that in the 

 eastern and southeastern part of Wisconsin, the lime from the sub- 

 soil and rock of the regions surrounding the marsh is dissolved out 

 by the waters percolating through the soil and carried to the marsh 

 so that these marshes are usually well supplied with lime and are 

 not acid. (Wis. E. S. B. 205; F. B. 78; F. B. 320; F. B. 465.) 



ACID SOILS. 



The breaking down of organic matter in the soil is accompanied 

 by the formation of various organic compounds. The exact nature 

 of these compounds is not well known, though it is generally agreed 

 that certain organic acids are among the products. These organic 

 acids have been variously spoken of as humic, ulmic, crenic, and 

 apocrenic. Some writers have questioned the existence of such 

 acids, but it is very certain that the water extract of certain soils, 

 especially muck soils, does have a decidedly acid reaction, even after 

 it has been thoroughly boiled ; and since muck soils are made up al- 

 most entirely of organic matter, it would seem safe to assume that 

 acids result from the breaking down of the organic matter, at least 

 until this has been disproved. 



There are two principal effects produced by using lime on 

 soils : One of these is to correct the acidity of the soil, and the other 

 is to decompose the soil itself. To correct the acidity of sour soils is 

 certainly a very desirable and profitable use of lime. Clover, alfalfa, 

 alsike, cowpeas, soy beans, and many other legumes will not live or 

 will not thrive to the best advantage on soils which are strongly acid. 

 To be sure such crops can be made to grow on acid soils by liberal 

 applications of farm manure or other complete fertilizers but the 

 nitrogen gathering bacteria of the legume plants do not properly 

 develop and multiply in acid soils and consequently the legumes do 

 not have the power which they should have to accumulate large 

 quantities of atmospheric nitrogen by means of the bacteria which 

 inhabit, or should inhabit, their roots. Furthermore, the process 

 which is termed nitrification by which the nitrifying bacteria trans- 

 form the insoluble organic nitrogen in farm manure and plant 

 residues into soluble nitrate nitrogen, the form in which it becomes 

 available as plant food, is greatly promoted by the presence of lime 

 and retarded by acid conditions. 



