Seed production of two brachiaria hybrid cultivars in - Tropical ...

Seed production in brachiaria hybrids 33
crops established from tillers produced 60%
(Trial 2 vs Trial 1) and 117% (Trial 3) more seed
than seed crops established from seed. When
the components of seed yield were examined, it
appeared that the number of inflorescences and
seeds/m 2 were the most critical components of
yield. Crops planted with tillers produced approximately
20% more inflorescences and 90% more
seeds/m 2 than crops planted with seed.
Currently, 2 of the 3 most important grass seed
crops in Thailand, Ubon paspalum and Purple
guinea, are established by planting tillers. While
the third crop, ruzi grass, has usually been established
with seed, there has been a shift recently
towards planting tillers, because vegetative
plantings usually produce quick establishment.
Farmers also prefer to plant tillers because it is
similar to their traditional method of establishing
rice, in which rice is first sown into nurseries and
4- to 6-wk-old seedlings are then transplanted
into paddies. Identical practices are followed
with first-year grass seed crops. For subsequent
grass seed crops, plants in existing fields can
be dug up and rooted tillers divided and transplanted
into new seed fields. By planting grass
seed crops with tillers, farmers can plant in wide
rows, which facilitates weeding and harvesting
and leads to increased seed yields (Loch et al.
1999; Souza 1999).
Planting early in the wet season (May or June)
produced the most brachiaria hybrid seed in
3 out of 4 trials in the current study. Trial 3 was
severely affected by drought, with the wet season
rains finishing 6 weeks early, in mid-September,
2004. May- and June-planted crops in Trial 3
were defoliated in early August and, because of
the drought, regrowth was very slow, resulting in
seed yields similar to July- and August-planted
seed crops.
Inflorescence numbers and seeds/m 2 were
again the most critical seed yield components
determining higher seed yields from early establishment.
As planting date progressed through the
wet season, inflorescence numbers declined, but
raceme and spikelet numbers increased. However,
increased raceme and spikelet numbers did
not compensate for the lower inflorescence numbers
and seed yields declined. Hare et al. (2001)
also found that inflorescence and seed numbers
were the most important seed yield components
influencing seed yields of Ubon paspalum. When
both components declined with later planting,
seed yields also declined.
Forage production from grass seed crops is
extremely important for smallholder farmers in
Thailand. Farmers either feed the forage to their
own livestock or sell it as fresh grass to other
farmers (Khemsawat and Phonbumrung 2002) for
current (July 2006) prices of US$0.05–0.07/kg
fresh weight.
Planting early enables farmers to cut forage
from their seed crops before closing in late July–
early August (Hare et al. 2007a). The forage of
the brachiaria hybrids cut before closing was of
a very high quality in all trials, with a high proportion
of leaf (55–60%) and a high leaf crude
protein concentration that averaged over 15%. In
addition, the harvest stubble of brachiaria hybrids
in the trials remained green, the stems were not
hard and woody and the overall stubble was of a
good quality. Farmers have commented on how
the harvest stubble of brachiaria hybrids is far
more readily eaten by livestock than that of Ubon
paspalum, Purple guinea or rice, which are generally
very stemmy and fibrous. The stubble yields
of up to 25 t/ha DM will provide a valuable feed
resource for farmers in the dry season, when feed
supplies are limited.
While the low seed yields of Mulato have
proved to be not commercially viable, the better
seed yields of Mulato II in villages and in other
trials (Hare et al. 2007a; 2007b) are commercially
viable. To produce acceptable seed yields, brachiaria
hybrid seed crops should be hand-planted
with tillers early in the wet season. Early sowing
also enables high quality forage to be produced
before closing to seed.
Acknowledgements
We thank the Thailand Research Fund (TRF)
for providing financial support to this research
program and the Faculty of Agriculture, Ubon
Ratchathani University for research facilities.
References
CIAT (2004) Annual Report 2004 Project IP-5: Tropical
grasses and legumes: Optimizing genetic diversity for multipurpose
use. CIAT, Cali, Colombia.
HARE, M.D. and PHAIKAEW, C. (1999) Forage seed production
in Northeast Thailand: A case history. In: Loch, D.S.
and Ferguson, J.E. (eds) Forage Seed Production Volume 2:
Tropical and Subtropical Species. pp. 435–443. (CAB International:
Oxon, UK).
HARE, M.D., KAEWKUNYA, C., TATSAPONG, P., WONGPICHET, K.,
THUMMASAENG, K. and SURIYAJANTRATONG, W. (2001) Method