3. Results
In order to determine the response of vetiver to fertilization, the effects of different fertilizer levels in the irrigation water on growth of the plants were determined. Fresh water with low salinity (EC ∼1 dS/m), which is a common quality of fresh water in arid and semi-arid regions, was used for irrigation. Total dry foliage weight of vetiver plant for two harvests and the plants height at different dates for three fertilizer treatments are presented in Figs. 1A,B, respectively. The 2 mL/L fertilizer treatment, which contained 118, 15.2, and 72.2 mg/L N, P and K, respectively, was the optimal fertilizer level for obtaining maximum total dry weight of plant foliage in both harvests (Fig. 1A). No significant differences in plant height were observed between the 1 and 4 mL/L fertilizer treatments for the 1st harvest or among all three fertilizer treatments after the 1st harvest (Fig. 1B). Therefore, one regression line was plotted for the plant height data in the 1 and 4 mL/L fertilizer treatments before the 1st harvest and another line for the three fertilizer treatments after the 1st harvest (Fig. 1B). The elongation rate (the slope of the regression lines) of the longest leaf of the different plants in the three fertilizer treatments was higher after the 1st harvest (Fig. 1B). The average slope of the regression lines before and after the 1st harvest was <1.6 and 3.9 cm/day, respectively. Plant heights for the 2 mL/L fertilizer treatment were significantly higher than the other two fertilizer treatments from 30 days after planting until the 1st harvest (Fig. 1B). The exponential increase of the plant height in the 1 and 4 mL/L fertilizer treatments before the 1st harvest (Fig. 1B) indicated that a delay in the growth of the vetiver plants occurred during the beginning of the growing season in these two fertilizer treatments.
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