LEGUMES AXD GRASSES 



27 



Only age of grass showed any 

 statistical significance in rate of 

 water entry (table 17). Rate of 

 water entry for each time interval 

 beyond 10 minutes generally in- 

 creased with increased age of grass. 

 Four years of grass substantially 

 improved soil structure. Twenty- 

 year grass plots showed the highest 

 rate of water entry at all time 

 intervals. Bulk density of the sur- 

 face 3 inches of soil was signif- 

 icantly decreased by 6- to 20-year 

 grass stands. 



Their data (table 18) indicate 

 that the total nitrogen and oxidiz- 

 able organic matter in the surface 6 

 inches increased with the age of 

 grass stand. Nitrogen fertilizer 

 increased the nitrogen content of 

 the surface soil, but it had no 

 significant influence on the organic 

 matter. 



Mazurak and Conard (53) com- 

 pared rates of water entry into 

 soils of three Great Soil Groups 



when cropped for 7 years to various 

 grasses and small grains. Only the 

 data for the Chernozem and the 

 Chestnut soils are presented (tables 

 19 and 20). The Chernozem was 

 Holdrege fine sandy loam near 

 North Platte. The Chestnut was 

 Rosebud very fine sandy loam near 

 Alliance. On the Chernozem soil, 

 five cool-season grasses, four warm- 

 season grasses, and a wheat, fallow 

 rotation were compared. Only cool- 

 season grasses and a wheat, fallow 

 rotation were compared on the 

 Chestnut soil. Half of each plot 

 was fertilized with nitrogen each 

 spring. In both studies, moisture 

 content of the soils were near the 

 permanent wilting percentage when 

 rates of water entry were measured. 

 On both soils, the rate of water 

 entry for the first 10 minutes was 

 highest for the wheat, fallow rota- 

 tion plots. Infiltration rate was 

 determined when the land was in 

 stubble. On the Chernozem soil, 



Table 18. — Total nitrogen and oxidizable organic-matter contents oj soil by 

 soil depths, as influenced by the age oj grass and application oj nitrogenous 

 jertilizer, North Platte, Nebr., 1947-56 J 



Rotation and age of 

 grass (years) 



Annual ap- 

 plication of 

 nitrogenous 

 fertilizer, 

 per acre 



(2) 



Total nitrogen at 

 depth (inches) of 2 — 



Total oxidizable 



organic matter at 



depth (inches) of 2 — 



(1) 



to 6 



(3) 



6 to 12 



(4) 



to 6 



(5) 



6 to 12 

 (6) 



5-year grain fallow 



Grass: 



2 



Pounds 







/ 40 



1 o 



/ 40 



1 o 



/ 40 



1 o 



/ 40 



1 o 







Percent 

 0.092 



.097 

 .096 

 . 105 

 . 100 

 . 109 

 . 104 

 . 122 

 . 109 

 . 121 



Percent 

 0.088 



. 103 

 .098 

 . 102 

 .098 

 . 107 

 . 106 

 . 106 

 . 104 

 . 102 



Percent 



1. 6 



1.8 

 1.9 



2. 1 

 1.9 

 2.2 

 2. 1 

 2.4 

 2.2 

 2.7 



Percent 



1.6 



1.8 



4 



1. 8 

 1.9 



6 



1. 9 

 2.0 



8 _ 



2. 

 2.2 



20 



2. 



2. 







i Data from Mazurak and coworkers (54). 



2 Differences statistically significant (at the 5-percent level) for comparisons between ages and between fertilizer 

 and no fertilizer in column 3 and between ages in column 5. 



