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Regrowth and Nutritive Value of Setaria Splendlda Stapf at Different Cutting Intervals and Levels of Nitrogen Fertilization
Thesis Abstract:
An experiment was conducted at the Dairy Training and Research Institute (DTRI), University of the Philippines Los Banos (UPLB), from May to December 1992 to quantify the regrowth, weed invasion, and nutritive value of setaria grass (Setaria splendida) after defoliation. Setaria grass sward was cut at three cutting intervals (20, 40, and 60 days) and fertilized with nitrogen at three levels (50, 100, and 150 kg N/ ha).
Plant regrowth after defoliation was significantly affected by cutting interval. The 60-day cutting interval enabled the plants to recover their growth well. These plants produced more tillers, had higher leaf area, height, and dry matter yield. Even though a reduction in root growth occurred, it was less severe compared to those cut at 40 and 20 days interval. Likewise, at 60 days interval, some plant tissues reached their maximum growth rates as reflected by a high amount of standing dead and dead stubble per plant. There was no standing dead observed in plant cut at 20 days interval. With repeated defoliation, the rates of leaf emergence and root growth were retarded due to a decline in accumulated carbohydrate reserves. Hence, the plants' regrowth capability decreased from the first to the last cutting periods.
Weed growth at 60 days cutting interval was the shortest. The plant canopy covered more soil surfaces, thereby restricting the growth of weeds. There were more weeds (2.0 tons DM/ha) in those cut at 20 days cutting interval. However, the number of weed species noted were the same for all treatments.
No significant differences were observed in in vitro dry matter digestibility at different cutting intervals. At shorter cutting intervals, crude protein content remained higher than those in longer cutting intervals even though the leaf to stem ratio was lower.
Results suggested that the optimum cutting interval for S. splendida under an intensive forage production scheme (cut and carry system) was about 40 days, wherein regrowth and yie ld were high and the forage feed harvested was of good quality for the ruminant animal.
Setaria grass did not respond to the levels of nitrogen applied in this experiment. Therefore, a lower rate of nitrogen fertilizer (50 kg N/ ha) applied after each cutting may be sufficient to maintain the regrowth and productivity of a grass sward.