81 



A 

 B 



rh 





rti 





-s/S 



c 



___ 



s 



B 



C 

 B 



— 



C 

 

 N 



s 





S 



B 

 C 



B 





T 

 R 

 

 L 







S 







B 





1 



c 





B 



< 



S 



— ■■ — — * 



B 



C=CHIPS 



c 



B 



S 



S=SAND 

 B=BLANK 



B 





C 





Figure 12. Experimental design for adding builder's sand and wocd 

 chips to houses 1 through h at the tilling site. 

 Only the front two-thirds of the houses are shown. 



