| dc.description.abstract | This study was conducted to determine the effects of tractor-ploughing and handclearing
as land treatment methods on morphometric characters and aboveground
biomass production of Eragrostis superba, Cenchrus ciliaris and Enterepogon
macrostachyus. The study also evaluated the returns from range reseeding in eastern
Kenyan rangelands of Kitui district.
Seed viability was tested under laboratory conditions following standard procedures
using petri dishes over a period of 17 days. On-farm field trials involved
broadcasting seeds of the grass species in two land treatments; namely, tractorploughing
and hand-clearing. Each of the grass seeds were broadcasted randomly in
six sub-plots (6 m x 6 m) in both treatments at a density of 100 grams m-2
. Thirtyfive
plants were randomly selected per sub-plot and tagged for sampling.
Measurements of morphometric characters were taken weekly, whereas aboveground
biomass was estimated by harvesting standing grasses in the sub-plots after three
months of establishment. Data for economic analyses were generated from the costs
of physical inputs used and costs incurred at the time reseeding was done.
After 17 days of laboratory observation, C ciliaris had the highest percent
germination of 28.4%, whereas E. macrostachyus and E. superba had percent
germination of 20.1% and 8.6% respectively. These differences were attributed to
the intrinsic properties of the grass seeds such as dormancy and tegumental hardness.
To ensure successful reseeding in these ecosystems, it is necessary to determine that
grass seeds are viable for rehabilitation. Results obtained showed that land treatment
had a significant (p<0.05) effect on morphometric characters of grass species.
Seedling mortality was found to be significantly higher in the hand-cleared than in
the tractor-ploughed plots. In the tractor-ploughed plots, C ciliaris (10.5%), E.
macrostachyus (15.4%) and E. superba (24.8%) demonstrated lower percent
seedling mortality than those in the hand-cleared plots. Percent mortality was
relatively higher (C ciliaris (20.5%), E. macrostachyus (18.2%) and E. superba
(32.4%) in the hand-cleared plots than in the tractor-ploughed plots. Similarly,
foliage cover, plant height, leaf and tiller numbers in the tractor-ploughed plots were
significantly higher (p<0.05) than those in the hand-cleared plots. This scenario was
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attributed to the opening-up of the soil surface, which might have increased capture
of scarce rainfall water by the soil in the tractor-ploughed plots than in the handcleared
plots. Aboveground biomass was also significantly higher (p<0.05) in the
tractor-ploughed than in the hand-cleared plots at the milky stage of grass
development. This ranged from; 3,682.5 kg ha-l to 4,908.5 kg ha-l DM, 2,734.0 kg
ha-l to 3,240.0 kg ha-1 DM and 1,899.5 kg ha-l 2,434.5 to kg ha-1 DM for E.
macrostachyus, C. ciliaris and E. superba, respectively, in hand-cleared and tractorploughed
plots. Higher aboveground biomass in the opened-up plots than in the hard
soil surface plots was also attributed to increased capture of scarce water by the soil.
Of the three grass species tested, E. macrostachyus presented the best results for
ecological rehabilitation for the area while C. ciliaris and E. superba were the
medium and least suitable grasses, respectively.
An economic analysis demonstrated that investing in range reseeding using the two
land treatment methods are both economically viable ventures. Computations based
on the internal rate of return and benefit-cost ratio derived from the hypothetical sale
of hay revealed that a net annual profit of about 15.4% and 26.4% could be obtained
from the hand-cleared and tractor-ploughed investment respectively. This study also
demonstrates that reseeding a similar area using these treatment methods can yield a
benefit-cost ratio that is greater than one. Furthermore, E. macrostachyus, C. ciliaris
and E. superba are all economically feasible species for reseeding in the eastern
rangelands of Kenya. It is however recommended that, a study covering more than
two seasons be carried out, as this would yield more information on the
establishment of pastures under the two land treatment methods. Other potential
species such as Digitaria macroblephara, Cynodon dactylon, Chloris roxburghiana
and Themeda triandra should also be studied under different land treatment methods
so as to increase knowledge on how to capture the scarce water by the soil which
may be used to boost forage production and halt degradation in the rangelands.
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