A look-see at Vetiver Grass in Malaysia

2.2 EFFECT OF SPACING CUM FERTILIZER ON GROWTH OF VETIVER HEDGEROWS

In any terrain and soil condition, production of good quality hedgerows is mainly dependent on 3 factors:

The quality of planting materials used
The planting distance between clumps
The amount of fertilizer used

A trial was set up to test these using 3 spacing distances and 2 rates of fertilizer applications. Good quality 3-month-old polybag plants, selected for uniformity, were used for all treatments. The details of the trial are given in Photo 4.

The fertilizer treatments are:

Months Level F- 1 Level F-2

0 Kokei 6 gm - 1 nugget Kokei 6 gm - 3 nuggets

4 Kokei 6 gm - 1 nugget Kokei 6 gm - 3 nuggets

8 Kokei 6 gm - 1 nugget Kokei 6 gm - 3 nuggets

Field Field

King 15 gm - 1 nugget King 15 gm - 3 nugget

Kokei 15 gm - 1 nugget Kokei 15 gm - 3 nuggets

16 Kokei 6 gm - 1 nugget Kokei 6 gm - 3 nuggets

Field Field

King 15 gm - 1 nugget King 15 gm - 3 nugget

22 Kokei 6 gm - 1 nugget Kokei 6 gm - 3 nuggets

Field Field

King 15 gm - 1 nugget King 15 gm - 3 nuggets

24 Kokei 6 gm - 1 nugget

Assessments were based on determination of dry matter production from tops cut above 40 cm. Because of staff constraint, gap measurement was not started fill ten months later, at which time, it was not possible to measure the gaps between the 15 cm planting as the error would be too great (see previous discussion page 4).

RESULTS

In the First Progress Report the results of the first and second months were given. For easy reference and discussion, they are reproduced here.

(a) Photographic Record

Photo 5 Show the influence of planting distance on inter-clump gaps at 4 months after planting. Note that while there were still small gaps in the 15 cm, planting, the hedgerow would already be functional enough to slow down the speed of water rushing through the hedgerow. Also, the trapped twigs, leaves and other debris would help to retain the soil-wash.

Photo 6 Shows the good hedgerow formed by the 15 cm planting after 18 months. Note the neat dense and compact hedgerow with uniform good growth.

Photo 7 Shows the hedgerows of 3 planting densities at 19 months after planting. Note the big inter-clump gaps at the 60 cm planting.

Photos 8, 9 & 10 Show 2 different views of the hedgerows at 24 months after planting. Large inter-clump gaps are evident in the 60 cm planting; this hedgerow is still not functional to protect soil erosion. Small gaps still exist in the 30 cm planting and the individual clumps are still observable. The 15 cm planting has become a defined and integrated hedgerow. There was no inter-clump gap and the individual clumps cannot be observed.

Photo 11a & 11b Show the good quality of Vetiver clumps with active evenly distributed growth.

Photo 12a & 12b Show conditions where the "centre" has died.

Photo 13a & 13b Show the result of layering the older culms in the 60 cm planted hedgerow. Only 10.3% of inter-clump gaps were filled with new plants.

(b) Inter-clump Gaps

Inter-clump gap measurements were only started when the trial was 10 months old and only involved the wider spacings of 30 cm and 60 cm plantings. It was not possible to measure the 15 cm planting as the gaps would be too small for accurate measurement (see page 4).

Table 4 and Figure 3 summarise the results from 10 to 25 months. Improvement from higher fertilizer rates was marginal and was generally not significant. Spacing has highly significant (P< 0. 001) effect with the 60 cm planting having consistently higher gaps than the 30 cm planting. Table 5. summaries the variations in the plot cv. CV of 60 cm plantings is consistently lower than that of 30 cm plantings. This is largely because of the bigger interclump gap measurements. There appears to be a slight increase in cv for the 30 cm plantings from 19 months onwards. This could be due to certain dying out of the clumps and will be discussed later.

Table 4 also summaries the gap reduction which quantifies the rate of closure of the inter-clump gaps. The 2 rates of fertilizer application did not have any effect. However, spacing effect was highly significant in the earlier periods of 10-12, 12-13 and 13-15 months with the 60 cm plantings closing at a much faster rate than the 30 cm plantings.

From 19 months onwards, we noted certain die-back in the centre of the clumps. This situation became worse by the 24th month. Photos 11a & 11b show the good clumps while Photos 12a & 12b show the "centre" has died. This is mainly in the replications, which became more shaded as the neighbouring Hevea trees canopy develops. In addition, it was also observed that these weaken plants subsequently succumbed to termites attack. All these will have very adverse effects on the measurements and therefore the trial was terminated at 25 months.

The results are given in Table 6a & 6b and Figure 4. Generally the fertilizer effect was marginal and significant only up to the 7th month. The higher level of fertilizer produced higher top dry matter. The significant difference in the 25th month was surprising and may have been confounded by the dying off of centre of certain clumps.

Spacing did not have any effect in the first 2 months. Thereafter the lower spacing treatment produce consistently higher dry matter than those planted closer.

(d) Top Dry Matter Production per 10 m Run

The results are summarised in Tables 7a & 7b and Figure 5. The fertilizer effect is similar to the results for dry matter per clump given above; the higher level of fertilizer application produced significantly more dry matter than the lower level for the first 7 months. The dry matter production per 10m run is influenced by the production per clump and the spacing, which determined the number of clumps per experimental plot. The effect of spacing was observed from the first month. The closest planting distances of 15cm have the highest gramme per 10m run up to 7 months largely because of the higher number of plants. The 30 cm planted hedgerow catches up with the 15 cm, from the 8th 10, 13, 15, 18, 19 and 23rd months; it even surpasses the production by the higher density planting at 22nd and 23rd month. The 60cm planting produces significantly lower dry matter per unit length (gramme per 10 m) over the entire 25 months period suggesting a much poorer hedgerow.

(e) Layering

After recognising that the inter-clump gaps will close very slowly for wider spacing planting, attempts were carried out to fill the resultant gaps with new plants by layering the older culms from adjoining clumps along the hedgerow. Observation on 68 gaps showed that the success was poor at 10. 3 % only (Photo 13). This differs from other results (85.9% success) of layering the culms perpendicularly away from the hedgerow. The most likely reason is self-shading by the clumps in the hedgerow itself. Therefore this approach will not be satisfactory. Closer planting should be used from the start to produce good hedgerows.

DISCUSSION AND CONCLUSION

Since this was only an observation trial for practical application the conclusions are tentative. More fertilizer treatments and wider range of spacing would be preferred. Additional fertilizer seemed to have an effect on dry matter production in the early months, but the higher level did not produce any increase later. Spacing plays a big role in dry matter production; the wider spacing produces significantly higher dry matter per clump. The reverse was noted in dry matter production per linear distance, reflecting the interaction of individual plant growth and the planting density. There is an apparent time x density interaction and 30cm spacing seem to have caught up with the 15cm spacing after 8 months. However, 60cm spacing stayed consistently lower. The dry matter studies, the measurement of inter-clump gaps and gap reduction strongly indicate that close planting of 15 cm is preferred for quick establishment of a functional hedgerow. Use of layering of culms to fill the gaps between wider spacing is of little value.