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Robinson, F.E. 1993. Response of kenaf to multiple cutting. p. 407-408. In: J. Janick and J.E. Simon (eds.), New crops. Wiley, New York.

Response of Kenaf to Multiple Cutting

Frank E. Robinson

  1. METHODOLOGY
  2. RESULTS
  3. DISCUSSION
  4. REFERENCES
  5. Table 1
Kenaf thrives in the desert area of El Centro, California (Robinson 1988). The high protein content of the leaves may offer promise as a forage crop, if the plant can survive multiple harvest as it does in Oklahoma (Phillips 1989). A project was initiated to examine the response of 11 kenaf cultivars to multiple cutting. Treatments consisted of: (1) a single cut in the fall on Oct. 24, 1990; (2) two cuts on July 2 and Nov. 9, 1990; and (3) three cuts July 2, Sept. 10, and Nov. 7, 1990.

METHODOLOGY

The plot area was 56 rows wide by 12 m long. The kenaf was field sown on Apr. 3, 1990 with two rows per 1 m bed and furrow irrigated. Soil was an Imperial clay; fertilization was 110 kg N/ha applied as urea preplant, and two sidedress applications of 55 kg N/ha. Superphosphate was applied preplant at 110 kg P/ha. Colorado river irrigation water contained 5 ppm K, so the 20 irrigation applications made during the 30 week crop period supplied approximately 101 kg K/ha. We left 3 m of each row uncut until final harvest. The remaining 9 m of each 4 row plot was cut two nodes above the soil surface (Phillips 1989) on July 2; of these 3 m were allowed to regrow until harvest. On Sept. 10, 6 m of the original 9 m of the plot were cut again and allowed to regrow until harvest. This produced 3 m cut once at the final harvest, 3 m cut twice i.e. on July 2 and at final harvest, and 6 m cut three times July 2, Sept. 10, and at final harvest. At each cutting, the diameter of the stems in the center 3 m of two rows in each cultivar were measured either at the ground surface or next to the main stem where side shoots originated. Stem heights and weight, leaf weight, and plant density were determined. Sub-samples were taken and oven dried at 65deg.C to calculate percent dry weight. A single 6 m strip of two rows on the border was cut at the soil surface to observe regeneration.

RESULTS

The stems cut for the first time had no side shoots and only 30% of the stalks cut at the soil surface regenerated. Those that grew after being cut two nodes above ground developed multiple side shoots. Cultivar means were 2.6±1.1 shoots for second cutting (10 Sept.) 2.3±0.9 shoots (Nov. 9), and 2.6±1.3 for a third harvest on Nov. 7.

The multiple cuts produced thinner stems. Shoot diameters were 9.9±4.2 mm and 8.4±6.8 mm for second cuts, 7.6±3.8 mm for the third cut as compared to 17.5±1.0 mm for the single cut at final harvest.

The height of the stalks was greatly reduced by multi-cutting. The treatment with the tallest stalks (3.1±0.2 m) was uncut until final harvest. The stalks cut on 2 July were 1.4±0.2 m with regrowth reaching 1.5±0.7 m by Nov. 9. The treatment with three cuts was 1.1±0.3 m on first regrowth and 0.4±0.2 m at the second regrowth at final harvest.

The cumulative result of the shorter, thinner, multiple stems on the cut treatments was a leafier harvest which should provide a more palatable forage. Total yield comparisons are shown in Table 1.

DISCUSSION

Our results indicate that kenaf grown for forage should be cut two nodes above ground, rather than at the soil surface as is alfalfa. The treatment with one intermediate cut before the final harvest produced the best forage with highest leaf percentage and thinnest stems. A 2.5 t loss in total stalk yield was accompanied by a 1.4 t increase in total leaf production increasing the percent leaf dry matter in the total harvest from 12 to 20%. A second intermediate cut in September caused a large 6 t reduction in total stalk yield while increasing the total leaf yield only 0.5 t as compared to the single intermediate cut. Moving the first and second cuts up to earlier dates may produce a higher total yield and should be explored.

REFERENCES

Table 1. Total kenaf dry matter yields with either one harvest on Oct. 24, total of two harvests on July 2 and Nov. 9, or total of three harvests on July 2, Sept. 10, and Nov. 7.

Stalk (t/ha) Leaf (t/ha) Leaf (%) Total yield (t/ha)
Harvests Harvests Harvests Harvests
Cultivar 1 2 3 1 2 3 1 2 3 1 2 3
CV-34Sp 22.1 18.3 12.4 2.6 4.3 5.0 13.7 19.2 28.9 25.0 22.6 17.4
Xiang 21.6 20.1 13.0 2.7 4.4 5.1 12.9 17.9 28.1 24.7 24.5 18.1
E-41 20.4 18.4 8.9 3.2 5.2 5.3 10.4 21.9 37.0 23.9 23.6 14.2
Tainung 1 19.7 16.7 8.8 3.0 5.2 4.5 13.0 23.6 33.8 23.1 21.9 13.3
45-9X 19.3 13.0 10.2 3.0 3.4 4.5 11.9 20.9 30.8 22.8 16.4 14.7
RS-10 18.9 16.4 10.2 2.8 4.8 5.0 13.3 22.5 33.0 21.9 21.2 15.1
CV-34 18.8 17.0 11.4 2.2 4.0 4.8 10.2 19.2 29.8 21.5 21.0 16.2
G-45 18.8 16.4 8.9 3.0 4.0 4.4 10.9 19.8 32.8 22.1 20.4 13.3
E-71 18.2 17.7 11.7 3.0 3.1 4.5 12.4 14.8 27.7 21.6 20.8 16.1
C-108 17.8 15.9 8.7 2.5 3.9 4.3 13.4 19.6 32.8 20.7 19.8 13.0
C-2032 17.0 16.1 9.2 2.7 4.9 5.3 13.2 23.3 36.5 20.2 21.0 14.6
Mean 19.3 16.9 10.3 2.9 4.3 4.8 12.3 20.3 31.9 22.5 21.2 15.1
SD 1.5 1.7 1.5 0.3 0.7 0.4 1.2 2.5 3.0 1.5 2.0 1.6

Last update April 23, 1997 aw