APRIL, 1909 CIRCULAR No. 4 



CORNELL UNIVERSITY 



AGRICULTURAL EXPERIMENT STATION OF 



THE COLLEGE OF AGRICULTURE 



Departments of Soils and Agricultural Chemistry 



SOIL DRAINAGE AND FERTILITY 



Crop yields on many soils in this state are less than when the land 

 was new. The yields in New York State are much lower than in Eng- 

 land, notwithstanding the centuries of cultivation and cropping in that 

 country. England passed through a period of low yields, yet has not 

 only returned to its original productiveness, but has increased it. 



Some fundamental reasons for the decrease in yields are: 



(a) Decrease in humus, or decayed vegetable mold. 



(b) More extreme fluctuations in the moisture supply of the soil. 



(c) Tendency of some soils to become acid or sour. 



(d) Need of more intensive cultivation because of the above con- 

 ditions. 



A. Humus 



Uses of tJie humus in- the soil are: 



(i) When soils are well supplied with humus they are more easily 

 tilled. As the humus is burned out under cultivation, many soils tend 

 to compact. This is seen on clay soils that have been plowed while 

 wet. The presence of humus helps to bring about a granular condition 

 of the soil and to prevent the formation of clods. 



(2) Soils well supplied with humus have a better and more uniform 

 water supply. A granular condition of the soil enables it to hold a larger 

 amount of water and in a form available to plants, thereby giving the 

 plants a larger reservoir of water, and enabling them to withstand longer 

 periods of drought. Under these conditions artificial drainage is not so 

 necessary. 



(3) Soils well supplied with humus have more plant food and in 

 a more readily available condition than soils not so supplied. The 

 humus contains all the nitrogen of the soil. There is no nitrogen in the 

 rock particles of the soil. The nitrogen becomes available as food for 

 growing plants as the humus decays. In the decay of humus there are 

 acids formed which help to dissolve the rock particles and make their 

 plant food available. 



Three sources of humus supply are: 



(7) The remains of crops, as roots, stubble, etc. This source is in- 

 sufficient in soils under cultivation. 



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