Knowledge of the morphological and physiological responses of the
plant on the specific soil and climatic conditions of each region is fundamental for
determining management of defoliation recommendations and more efficient
fertilizer to encourage the soil-plant interface. The objective was to evaluate the
best time to cut the palisadegrass Marandu (Urochloa brizantha cv. Marandu)
submitted to different levels of fertilization (zero-00:00:00, low-100:32:100,
medium-170: 55 170 and High-240:78:240 N-P2O5-K2O) associated with different
times of defoliation (90, 95 and 100% light interception) for different seasons
(transition dry/water - D/W, period of the water - W and the water/dry - W/D).
Therefore we conducted two studies, the first to determine the effect of fertilizer
levels and the second to assess the effect of interception of photosynthetically
active radiation - IRPA on the performance of palisadegrass Marandu the
seasons. The work was composed of portions of 4x3 m² with three replicates per
treatment, which were distributed in a completely randomized design (CRD). The
first work was evaluated in repeated measurements over time and the second in
a factorial arrangement 4x3. The tiller population density (TPD tiller-1 m2
), height
(cm) and leaf area index (LAI m2 m2
) were strongly influenced by fertilization
strategies but were stable after the first evaluation. The senescence rate leaf
(SRL) has shown to be quite variable with the seasons, in which the lower
fertilization had an increase in 30,2% daily SRL compared to higher fertilization.
The leaf elongation rate (LER mm tiller-1 day-1
), stem elongation rate (SER mm
tiller-1 day-1
) and Phyllochron (PHYLLO days-1 sheet-1
) were influenced by the
seasons of the year, which provided the highest LER and SER at the time D/W,
the PHYLLO tended to decrease with increasing soil fertility and on average the
lowest value of 9,6 days-1
leaf-1 obtained for the high fertilization and among the
seasons the lowest value obtained for PHYLLO was at the station D/W with an
average of 9,1 days-1
leaf-1
. The lifetime leaf (LTL days) was not flexible to
treatment, the length of sheath (LS mm tiller-1
) and the number of living leaves
(NLL sheets-1
tiller-1
) proved to be greatly influenced by the treatments and
especially the time of year where the largest LS was obtained at the station D/W
with an average of 359,6 mm-1
tiller-1
, provided mainly by the low number of tillers
that resulted in higher LS to reach the goal target 95% of IRPA and for the same
period showed the highest NLL with an average of 4,9 leaves-1
tiller-1
. The total
dry matter (TDM kg ha-1
) of leaf blade (DMLB kg ha-1
), stem (DMS kg ha-1
) and
dead material (DMDM kg ha-1
) were influenced by the treatments, which both rise
fertility as the interception of light increased the production of dry matter (DM),
however, the increase provided after LAIcrítical was mainly due to the increase
of stem and dead material, and this response promoted the reduction in the ratio
L/S, which resulted also decreasing the SPAD index, which rose from 18,3 in
90% IRPA to 11,2 in IRPA 100%, this fall, demonstrates reduction in the
nutritional status of the plant. The accumulation rate of forage (ARF kg ha-1 day 1
) was influenced by fertilization strategies, where most fertilization provided an
increase of 204,6% in ARF compared to zero dose. Thus, we conclude that the
morphogenetic and structural characteristics of palisadegrass Marandu and their
forage production are strongly influenced by growing seasons and the
management of fertilization is fundamental to the realization of fertilization
associated with favorable environmental conditions for good forage production
both quantitative and qualitative. Finally, the next time the canopy 40 cm
coincides with the LAIcrítico, which is the optimal time for the defoliation of the
plant under edafoclimatic factors tropical conditions.
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