IQ'2 N. H. AGR. EXPERIMENT STATION. [Bulletin 138 



It can be easily reasoned out that the thin soil must be the 

 most quickly exhausted and require the most systematic feed- 

 ing with fertilizers, and if this soil is subject to easy drainage, 

 soluble chemicals in excess of plant needs will wash out and 

 be lost, since there is seldom much opportunity for capillary at- 

 traction to bring up water through sand or gravel. 



Loams overlying clay are in a whollN' different situation. 

 Drainage is slow, capillary attraction is strong and soluble ele- 

 ments of fertility remain in place until the plants can make 

 use of them, hence the term "strong." 



Humus. 



One of the most important constituents of a soil is the brown 

 or black vegetable matter, called humus, a substance which has 

 always received much attention from agricultural chemists. It 

 is produced during the decay of vegetable matter, in the pres- 

 ence of moisture, and is a mixture of compounds, some of which 

 are known, while some, perhaps many, are not yet identified. 

 Humus may thus have a variety of properties due to its com- 

 plex character. It is usually obtained in analysis by extracting 

 it from the soil with strong ammonia water. ]\Iany views have 

 been held with regard to its relations to crop production and 

 opinions have changed from period to period as new facts have 

 been observed and new truths worked out. But throughout the 

 century or more of study and argument, humus has always been 

 recognized as one of the leading factors in making a fertile soil. 

 It is the object of this bulletin to show how much luimus there 

 is in our soils and how to maintain it as an effective constituent. 



Types of Soil Studied. 



Three different types of soils on the college farm have been 

 examined and they are classified by Professor Taylor as clay, 

 clay loam and sandy loam, respectively. The sandy loam forms 

 only a small part of the farm and exists in low rolling ridges or 

 knolls formed by the water of the glacial period. Borings to 

 the depth of thirty inches show the loam to be underlain by a 



