LONCHOCARPUS, DERRIS, AND PYRETHRUM CULTIVATION 21 
Manguel * observed that only one-third as many man-hours were neces- 
sary to hand-weed derris plots mulched with 6 inches of sugarcane 
leaves as compared with control plots not mulched. 
Although the application of cane trash constituted an additional 
labor cost, yields were in some cases 31.7 percent greater, and rotenone 
content of the roots was slightly, although not significantly, higher than 
those of control plots. They recommend mulching as a commercial 
practice when suitable material can be applied economically. In an 
unpublished comment to the writer, White remarked that a good mulch 
decreased the amount of rooting at the nodes, thereby aiding removal 
of the vines. 
Harvest Methods and Yields of Roots 
Clearing the tops from a field of unmulched trailing derris (fig. 13) 
is complicated by the tendency of matted vines to become rooted to 
the soil. These tops are removed by cutting the thick blanket of 
Figure 13.—Derris elliptica; ground cover of leaves and vines is cleared away 
preparatory to digging the roots. Vines are cut by machete and then rolled 
into piles with long poles. 
vines into strips about three rows wide and 18 to 20 feet long. 
Machetes are used to sever the mat from the ground. This is rolled 
up and moved aside as it is cut loose. Once the vines are out of the 
way, the field can be plowed either with a tractor or with oxen. 
> Waite, Davip G., MULCHING TROPICAL PLANTS; and Wuite, Davin G., 
PaGan, CALEB, and ManGueLt Jos& C., THE EFFECTS OF MULCHING DERRIS 
ELLIPTICA. [Manuscripts accepted for publication in Journal of Tropical Agricul- 
ture (Trinidad).] 
783559°—48 4 
