102 BULLETIN 1105, U. S. DEPARTMENT OE AGRICULTURE. 



are thought to be due to unequal distribution of tree roots. Herbace- 

 ous vegetation is believed to have been a relatively unimportant fac- 

 tor, because it was sparse and closely cropped by cattle. 



A survey of all the soil-moisture data shows a fairly consistent 

 superiority of brush-covered over uncovered ground during dry 

 periods. Against this stands the fact that only in a single instance, 

 namely, the 1914 experiment previously described, has a brush cover 

 proved a really effective aid to reproduction. This discrepancy is 

 in a considerable measure explained by the fact that seedlings can 

 not grow directly under a dense mat of brush, where the greatest 

 benefits in the way of moisture conservation are secured. Seedlings 

 can grow only under a light cover, in the edges of the larger 

 brush masses, or in openings between branches. Even these situ- 

 ations afford considerable protection against water loss; but, as will 

 be shown later, the seedlings may be forced to yield these benefits 

 to older and more aggressive plants. 



Table 24. 



-Available soil moisture (percentage of dry weight), brush experi- 

 ment, Fort Valley, 1919-20. 





1919. 



1920. 





June 6. 



June 30. 



Aug. 2. 



Aug 



.30. 



Sepl 



.15. 



May 17. 



June 4. 





» 





& 





% 





8 





i 















f! 





■S 





■a 





% 





f? 







i 



1 





§ 





a 



8 



.3 



n"? 



B 



8? 



a 



a> 



.3 



gj 



% 



<8 





o 



I 



CO 



2 



I 



co 

 o 



! 



CO 



o 



1 



CO 



o 



■8 



a 



a 



1 



a 





tN 



co 



<N 



o 



<M 



CD 



CN 



co 



<M 



o 



CO i-i 



CD 



•-< 



No brush 



6.2 



10.8 



-,.2 



0.6 



22.8 



15.6 



7.8 



6.0 



3.2 



2.9 



7.0 ' 9.2 



4.5 



8.3 



Between branches. 



12.3 



10.4 



-1.0 



4.5 



22.4 



18.2 



12.2 



7.6 



17.3 



11.7 



6. 1 6. 6 



3.9 



4.7 



Under branches... 



15.8 



12.3 



-0.9 



3.4 



21.5 



15.4 



12.9 



7.6 







6.8 7.9 



6.0 



7.0 



Under litter 



17.7 



11.9 



-0.1 



2.0 







13.7 



9.2 













North edge of 











" "| 







brush pile 



18.6 



14.8 



6.1 



3.9 







18.4 



14.2 





















\""\ 







June 19. 



July 6. 



July 13. 



Aug. 9. 



Sept. 3. 



Oct. 6. 



Nobrush 1.8 5.0 



Between branches 2. 4 ■ 2. 



Under branches 1.8 2.1 



0.0 

 -o..; 

 1.0 



2.9 

 5.7 

 2.9 



-0.2 



-0.6 



0.6 



7.0 

 3.9 

 2.0 



6.4 

 7.9 

 9.0 



4.1 

 3.9 

 3.4 



0.1 

 4.0 

 6.8 



2.7 

 -1.3 



0.6 

 0.9 

 1.9 



5.0 

 2.3 

 4.7 



Wilting coefficient: Per cent. 



1919. Depth, 2 to 3 inches 7.8 



Depth, 6 inches 11.3 



1920. Depth, 6 inches 13.1 



Depth, 12 inches 15.4 



i Interpolated July 13. 



