LEGUMES AND GRASSES 



29 



Table 20. — Rates, at several intervals, of water entry into a Chestnut soil 

 after 7 years oj grasses and wheat, fallow, Alliance, Nebr., August 1952 l 



Species or rotation 



Rate of water entry, per hour, at end of- 



o 



min. 



10 

 min . 



20 



min . 



40 



min. 



60 



min , 



120 



min. 



420 



min . 



Cool-season grasses: 



Agropyron smithii (western 

 wheatgrass) 



Agropyron desertorum (desert 

 wheatgrass) 



Agropyron cristatum (crested 

 wheatgrass) 



Elymus junceus (Russian 

 wildrye) 



Agropyron intermedium (in- 

 termediate wheatgrass) 



Bromus inermis (smooth 

 brome) 



Mean 



Wheat, fallow 



Least significant difference 

 (5-percent level) between 

 means 



Cm. 



10. 2 



11. 5 

 11. 6 



8. 5 



9. 6 

 7. 2 



Cm. 

 8.4 

 8. 4 

 8. 2 

 7. 1 

 6. 3 

 5. 8 



Cm. 

 1.1 

 6.3 

 6.3 

 5. 6 

 4.7 

 4. 8 



Cm. 

 7.2 

 5.0 



5.4 

 4. 1 

 3.4 

 4. 



Cm. 

 6. 9 

 4. 7 

 4. 1 

 3.4 

 2. 9 

 3.8 



Cm. 

 6.4 

 4. 4 

 3.3 

 2. 6 



2. 5 



3. 5 



Cm. 

 6. 1 

 4. 7 

 2.8 

 2.3 

 2. 4 

 3 6 



9. 8 



7.4 



4. 8 



4. 3 



3.8 



5. 6 



14. 1 



10. 



5. 4 



4. 4 



2. 4 



4. 4 



2. 6 



2. 1 



2.3 



2.5 



2.7 



3.0 



i Data from Mazurak and Conard (55). 



readily oxidizable materials. Blue 

 grama, buffalograss, bromegrass, 

 bluegrass, and orchardgrass pro- 

 duced the highest organic-matter 

 contents. Side-oats grama, blue 

 grama, bluegrass, and bromegrass 

 imparted the greatest stability to 

 soil aggregates as measured by the 

 percentage of soil aggregates greater 

 than 0.25 mm. diameter. No sig- 

 nificant difference was found for 

 measurements of pore-space satu- 

 ration, or volume weight. 



Their findings indicate that or- 

 ganic-matter content was higher 

 and physical condition of the soil 

 cropped to grass was better than 

 that in an adjoining cultivated 

 field. Stable soil aggregates were 

 correlated with total nitrogen con- 

 tent and readily oxidizable material, 

 but they were not closely related to 

 the vegetative production of the 

 various grasses. Differences in ag- 



gregate stability were attributed to 

 differential root development of the 

 grasses. 



After 2 years of small-grain crop- 

 ping, McHenry and Newell (49) 

 again determined the water-stable 

 aggregates in the soil from the same 

 plots as sampled in their previous 

 study. Water-stable aggregates 

 greater than 0.25 mm. had de- 

 creased an average of 70 percent in 

 all grass plots except buffalograss 

 plots. Buffalograss plots decreased 

 approximately 50 percent in aggre- 

 gate stability. 



Duley and Domingo (18) made 

 infiltration tests on several grassland 

 soils to determine the effect of grass 

 cover on infiltration. A sprinkler- 

 type infiltrometer was used. The 

 total cover, including live grass and 

 associated litter, affected infiltra- 

 tion more than the kind of grass or 

 the type of soil. There was little 



