MSc

Pennisetum polystachyon (L.) Shult. and P. pedicellatum Trin. are two
major grass weeds that are widespread in young plantation crops and non-arable
areas of the tropics. The present investigation was undertaken to have an
understanding on the biology, growth behaviour and fodder production potential of
these two Pennisetum spp. at the Research F~ College of Horticulture,
Vellanikkara during 1998-2000.
Germination tests were conducted at monthly intervals. P. polystachyon
did not show any dormancy and started germination as soon as the seeds are
collected (December). P. pedicel/alum seeds remained dormant during December
and January and it started germination by February only. Both species showed
above 80 per cent germination by late March. Germination percentage started to
decline in P. polystachyon after April.
Phenological characters of both species were noted from a natural
population during the year 1999. Seeds of Pennisetum spp. started germination
soon after the receipt of monsoon showers by the end of April. Flowering started
after the completion of the rainy period in September. Plants started senescence by
mid December in P. polystachyon and mid November in P. pedicellatum.
Both Pennisetum species studied showed remarkable regeneration
ability from different cutting heights. The percentage of plants regenerated was
similar in both species. Allelopathic reactions of roots, leaves and seeds were also
studied. Boiled and unboiled extracts were prepared and germination test were
conducted using cowpea, bhindi and cucumber as test crops. The cold and boiled
leaf extracts of both species did not show any effect on germination of test crops.
However, cold root extract of both Pennisetum spp. reduced the germination
percentge ofbhindi. Cold root extract of both species also showed some promotery

effect on shoot length in cowpea. Seed extracts showed inhibitory effects only on
cowpea germination.
Growth was comparatively fast in P. pedicellatum than P. po/ystachyon
during its early stages. P. polystachyon showed higher leaf : stem ratio than
P. pedicellatum. Growth indices like LAR, LWR, RGR, AGR and NAR were
similar in both Pennisetum spp.
In terms of total green fodder production, P. pedicellatum was superior
to P. polystachyon. Two cuttings, one at 70 days after sowing and the other just
before flowering recorded maximum fresh weight of fodder. Though crude protein
content was similar in both the species, P. pedicellatum showed a higher crude
fibre content than P. polystachyon. The results indicate that as the fodder quality is
good, utilizing these grasses as cattle feed can be one of the strategies for
managing them. However, cultivation of these grasses for fodder purposes involves
some risks because of their high reproductive capacity and persistence.