The Effect of Plant Population on Kenaf Yield
S.W. Neill and M. E. Kurtz
Population trials were conducted at several locations in the
Mississippi Delta during 1989 through 1992 (Table 1). The results
generally showed that the higher the plant population, the greater
the yield. However, the data in Table 1 can be misleading at the
lower populations because kenaf plants spaced widely apart tend
to grow large trunks (34 inches in diameter) and branch
excessively, and are therefore able to keep yields at a relatively
high tonnage. This phenomenon has caused difficulty in the harvesting
of research plots and is believed to present the same problems
for commercial harvests. More input by end product users will
determine if this is a desirable characteristic or one to be avoided.
Another characteristic of kenaf that is somewhat worrisome
is the selfthinning of the plant stand that takes place
through the growing season. Final plant stand can often be as
much as 20 percent less than that at a month after emergence.
Some of the lower treatments in Table 1 are the result of this
characteristic. The thinning is much more prevalent in the wider
spacings than the narrow because of intraspecific crowding along
the row. A mature kenaf stalk can have a base diameter of 1.5
to 2 inches at ground level and will usually thin down to about
five plants per foot of row. The only way to increase plant population
on a per acre basis is to narrow the row spacings. Literature
review indicates a desired plant population of approximately 80,000100,000
plants/acre.
Bast ratio is a component that can be directly manipulated
by plant population. Bast ratio increased as the plant population
increased, most likely because of competition for nutrients and
sunlight. This crowding effect resulted in smaller stalk diameter.
Stem diameter is considered a component of yield along with height,
and populations at higher populations tend to produce stalks shorter
and smaller in diameter than plants at the lower population levels.
End user specifics could have a role in the plant population levels
selected.
Table 1. Population trial results 1989 thru 1992 at all locations.
Stoneville
Leverette
1990 1991 1992 1992
Treatment 1989 1990 Glendora Field 13 Field 13 Field 16
plants/acre) ---------------(tons/acre)-------------
17,000 4.9 1.6
35,000 5.3 1.9 2.5
52,000 2.9 6.3 2.3
70,000 3.2 5.3 4.7 6.0 2.2 3.3
87,000 3.0 5.2 5.1
104,000 5.9 5.6 3.8
280,000 4.3