-J0"2 X. H. AGR. EXPERIMENT STATION. [Bulletin 13S 



and cropped with hay for three or four years, was 4.50 per cent. 

 The average difference in humus between these two classes of 

 grass land on the same soil was 1.23 per cent, which, calculated 

 for an acre to the depth of six inches, would be 18,450 pounds, 

 or over nine tons per acre. 



The new fields had of course received a dressing of manure 

 at seeding time, but the difference in humus would be equivalent 

 to organic matter in over thirty-five tons of manure per acre, 

 which is more than is ever applied in the practice of the farm. 

 Therefore a considerable part of the gain must have come from 

 the decay of the turf, roots and stubble turned under by the 

 plow. 



It is apparent that the marked decrease in the yield of hay 

 after three or four years' cropping is due in part to the decrease 

 in humus and its accompanying fertilizing constituents. 



Top dressing with chemicals helps for a time, but at length 

 they fail to yield profitable returns. In fact, their best results 

 have been produced when the field was still comparatively new 

 and before there could have been much decrease in humus. 



Available nitrogen is an important element in grass culture 

 and abundant humus will furnish it, provided the soil condi- 

 tions are favorable to the formation of soluble nitrogen from the 

 insoluble compounds of the humus. By the decrease in humus 

 and the lack of tillage, grass land gradually becomes deficient 

 in available nitrogen, while there may be many pounds per acre 

 locked up in the roots and turf in inactive combinations. 



Humus in Wet Clay Soil. 



There are many small areas of low wet land which are pro- 

 ducing but little on account of poor drainage. Frequently 

 such soils are considered to be muck beds, but usually they are 

 found to consist mainly of clay. They have a high percentage 

 of humus, however, due to the fact that the excess of water hin- 

 ders its destruction and favors its formation. In two such soils 

 the humus was found to be respectively 6.33 and G.40 per cent 

 and the total nitrogen was .49 per cent, the ratio of nitrogen to 

 humus being 1 to 13, or practically the same as in our clay soil. 



