IV. EFFECT OF FERTILIZER ON GROWTH OF VETIVER

Whereas it is generally claimed that Vetiver will grow under nutrient-stressed conditions and whereas it is also generally expected not to fertilize Vetiver hedgerows under normal practice, it is critical to know the response of Vetiver to fertilizer. This is especially so under special conditions where Vetiver hedgerows need to be established very rapidly. Examples are highways, dams, waterway constructions and housing areas in humid tropics with intense rainfalls. The different requirements of cut-earth and filled-earth are entirely different and have to be assessed.

Maximising production at economic cost is also important in relation to possible production of fodder.

Trial 1

This trial compares five treatments in four replicates as detailed and illustrated in Photo 23.

The use of slow release fertilizer is conditioned by two factors:

1. easy to control at application and therefore would not confound results. This is most critical for experimental purposes.
2. Economical to use in Malaysian context where labour is expensive.

Response to fertilizer application is by measuring the dry weight of cut-off tops at 40 cm at three months and four months after application (Photo 24) and the number of tillers produced at four months. The results as summarised in Table 9 and Figure 9 show:

1. Fertiliser aids in dry matter production and tiller production.
2. However, even without fertilizer application, the plants grow and multiply.
3. Increasing fertilizer application rates did not increase growth and multiplication rates significantly suggesting that the cheapest application rate of one Kokei nugget is sufficient.

Trial 2

This trial tests three treatments:

(1) K₁ + O : One Kokei nugget at beginning of trial.

(2) K₁ + K₁: One Kokei nugget at beginning of trial followed by another nugget after two months.

(3) K₁ + K₂: One Kokei nugget at beginning followed by two nuggets after two months.

Photo 25a shows condition of plants just after the second fertilizer application; Photo 25b compares plants grown under two treatments. Photo 26a and 26b show cut-of at 40 cm to measure dry matter production of tops. The main results are summarised below:

1. K₁ + K₂ increases the rate of height growth; while there was no difference between K₁ + O and K₁ + K₁ (Figure 10).
2. Dry weight of tops at three and four months were improved by a second round of fertilizer, but the two rates of application do not produce different dry matter production (Table 10 and Figure 11).
3. Tiller production was not affected by fertilizer treatment (Table 10 and Figure 12).
4. Dry weight of shoots and whole plant was increased by the second round of fertilizer application (Table 10).
5. Root production and % root/shoot were not affected by fertilizer application (Table 10 and Figure 12).
6. In general, increased fertilizer application resulted in higher nutrient value of the leaves and roots (Table 11).

CONCLUSION

These two trials show that fertilizer improves the growth and tiller production. However, increasing the amount of fertilizer application does not result in corresponding increase in productivity. Therefore, a minimum amount of fertilizer application of one Kokei nugget is sufficient for polybag plants raised to three months. Only for longer periods in another nugget necessary.