June, 1908.] HUMUS IN N. H. SOILS. !!•!> 



sod was in a plum i)lot, where it was serving as a cover crop. 

 The percentages of humus follow: 



Cl:iy soil. Rye Plot. 2.37 Fallow plot, 1.3G 



Alfalfa plot, 2.83 Corn plot, 1.97 



Clay loam. Clover plot, 2.51 Vegetable plot. 1.85 



Raspberry plot, 2.43 Vegetable plot, l.GO 



Fig. 2. — Vark'fi/ Plum Orchard on Clay Loam. 



The average loss of humus due to continuous stirring is .93 per 

 cent on the clay and .74 on the loam. Calculating these differ- 

 ences in pounds per acre to the depth of 12 inches, gives 28,000 

 pounds of humus in the first case and 22,000 pounds in the 

 second. 



On our soils removed generations ago from. the virgin con- 

 dition, it has not been easy to demonstrate clearly that loss of 

 humus necessarily meant loss of productive pOwer. 



But in the West it has been possible to demonstrate it, since 

 virgin soils and cropped soils could be directly compared. 



In both Minnesota" and North Dakota,^*^ comparative analyses 

 of virgin soils and wheat soils have shown marked losses in 

 humus. In the former state in eight years of continuous wheat 

 culture, the loss of humus was 17,000 pounds per acre, or over 

 one ton per year. In the latter state old soil cropped for seven- 

 teen years continuously was found to contain 1.56 per cent of 

 humus, while new soil showed 2.56 per cent. In another case 

 unbroken prairie contained humus equivalent to 109 tons per 



» Bull. 70, Minn. .\jrr. Exp. Stn. 



10 Bulls. 32 an<l 35. No. Dak. Agr. Exp. Sta. 



