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Bavec, F., L. Gril, S. Grobelnik-Mlakar, and M. Bavec. 2002. Production of pumpkin for oil. p. 187193. In: J. Janick and A. Whipkey (eds.), Trends in new crops and new uses. ASHS Press, Alexandria, VA.
F. Bavec, L. Gril, S. Grobelnik-Mlakar, and M. Bavec*
The Sajerska region in northeastern Slovenia and southern Austria has a long tradition of growing pumpkin (Cucurbita pepo L., Cucurbitaceae) as an oil crop. Oil types of C. pepo are also known as C. giromantiina var. oleifera Pietsch., syn. C. citrullina (L.) Greb. var. styriaca Greb. The seed oil is used for salad dressings but also has uses in pharmacology and alternative medicine (Wagner 2000), especially when produced organically. Oil content of pumpkin seed varies from 40% to 50% depending on genotype. The oil is dark green and contains free fatty acids. Vitamin E content, especially gamma-tocopherol, is very high (Hillebrand et al. 1996; Idouraine et al. 1996). The production of pumpkin seeds is on the increase and production techniques require further research (Bavec 2000).
Higher yield and more reliable production of vegetable cucurbits is often obtained with the use of transplants as compared to direct seeding (Spittstoesser 1990; Adams et al. 1993, Robinson and Decker-Walters 1997; Wien 1997). In this paper we review production of oil pumpkin by three methods: direct field seeding of dry seed, direct field seeding of pre-germinated seed, and the use of transplants grown in plugs.
The oil pumpkin establishment experiments were conducted at the University Agriculture Center Maribor, Faculty of Agriculture, Slovenia (43°34' N lat., 15°38' E long.) in 19971999. An overview of the experiment is presented in Table 1.
Table 1. Experiment overview.
|A. (direct seeding; non-germinated seed)||Planting depth 3 cm, 3 to 4 seeds per hill and thinned later.|
|B. (direct seeding; germinated seed)||Seed germinated in moist turf at 22°C, 3 days before sowing; 3 seeds per hill; planting depth of 3 cm.|
|C. (transplanting)||Sowing in plug trays on 1st May in 1997 and 1998, and on Apr. 29, 1999. Seedlings developed first leaves, second leaves in development stage. Seedlings were planted at the depth of cotyledons, one/hill and seedlings were irrigated at planting.|
|Cultivar||'Gleisdorfer Öilkurbis', a naked seeded pumpkin; oil content 43-45%; plant with long branched stems; registered in Slovenia since 1986; originally from Austria; seed germination 90%; seeds were treated with captan 50%.|
|Experiment design||Randomized block, 4 replications, 20 m2 (5 × 4 m)|
|Soil characteristics||Sandy-loam, 6.5 pH (n/10 KCl), 2% of humus, 9.5 mg P/100 g soil (Al extraction), 21.6 mg K/100 g soil (Al extraction)|
|Date of sowing and seedling plantings||May 16 in all years, sowing and planting were performed manually.|
|Fertilization||600 kg NPK/ha (7N:20P:30K) and 150 kg KAN-a/ha (25% N). N fertilization was made before sowing (1/2) and before flowering (June 14 in 1st year, June 26 in 2nd year).|
|Density||1.0 plant/m2, row spacing was 1 × 1 m. Young plants were thinned in treatments A and B on May 31.|
|Chemical protection||In the second half of June plants were infected with Erysiphe cichoracearum and Sphaerotheca fuliginea and protected with Bayleton special (triadimefon) at 0.5%. In the first half of August plants were infected with Pseudomonas lachrymans (Sm. Et Br.) Carsn.= Bacterium lachrymans Smith et Bryan|
|Weed treatment||Cultivated once in 1st year and twice 2nd and 3rd year. Stems were aligned on the plot many times.|
|Harvest date||Sept. 22|
Manual harvesting was carried out when 75% of fruits became yellowish-orange in color, the epidermal layer was easily pierced with a iron nail, and seed was dark green and well rounded. In 1997 and 1998 harvestable as well as unripe and decayed fruit were counted and diameter measured. Seeds were hand harvested and weighed. Seed moisture was analyzed on the basis of average sample weighing with standard drying procedure (3 days, 70°C).
Transplants were produced in plug trays in a heated greenhouse and seedlings were hardened before transplanting. Plug trays (28 × 50 cm) had 72 holes, each 3.7 × 4 cm, 5 cm deep. The volume was approximately 5.5 cm3. Plug trays were filled with the substrate (Asef) with one seed in every hole. Seeds emerged in well-lit area at day temperatures from 20° to 25°C and night temperatures 15°C. Five days after emergence plants were grown at 20°C. After 14 days at the first true leaf stage plants were transferred outdoors and covered with plastic during the night. After a month, seedlings were transplanted to the field location when they had 23 developed leaves, were 15 cm tall, and first flower buds were visible. Seedlings were well developed and roots survived transplantation without damage.
For costs calculation of oil pumpkin production expenses include direct costs (seed costs, substrate, fuel oil) and labor. The greenhouse was not amortized because a simple protective structure can be used. The price of pure nutrients was calculated on the basis of the prices of various mineral fertilizers.
Data was analyzed by the program Stat graphics + For Windows 2.1. Results (fruit weight, number of harvested fruits, number of decayed fruits, average diameter of fruits, weight of fresh pumpkins) were analyzed using analysis of variance and variance homogeneity test. Differences between individual treatments in each year was tested with Tukey test.
During the experiment the precipitation from May to September ranged from 565 mm in 1997 to 785 mm in 1999. In 1998 the second half of May was very cold which resulted in poor and uneven seed germination and slow growth of seedlings in the field. In 1998 and 1999 June, July, and August were warmer than 1997 compensating for the initial stagnation in plant growth.
Plants developed from direct seeding grew and developed more slowly in comparison to plants developed from transplants. Many morphological differences between treatments appeared in the beginning of June. Years and treatments had a significant influence on fruit yield, number of fruits, diameter of fruits, and seed yield in part to disease pressure (Table 2). In all years the transplants had the greatest fruit yield, highest number of harvested fruit, largest fruit, and highest seed yield. There were only small differences between the two seeding treatments and many were not significant. Average seed yields for 19971999 were 1.03 t/ha for direct seeding of dry seed, 1.27 t/ha for direct seeding of germinated seed, and 1.68 t/ha for transplants.
Table 2. Effects of direct seeding (non-germinated and germinated) and transplanting on seed yield and yield characteristics of oil pumpkin.
|Treatment (T)||Fruit weight (t/ha)||No. harvested (unripe and decayed)
|Fruit diameter (cm)||Seed yieldz (t/ha)|
|T × Y||ns||ns||ns||*|
z50% dry matter.
y means within column followed by the same letter are not significantly different at the 5% level (Tukeys test)
*, **, ns Significant at 5% (*), 1% (**), not significant (ns)
We conclude that seed yields of oil pumpkin are increased with the use of transplants but it is unclear if the use of transplants is justified economically. The cost in Euros (€) of 10,000 transplants, the minimum required population/ha was €0.04/plant or €400/ha. Calculations of oil pumpkins production costs with direct seeding (Table 3) indicate that expenses are acceptable if the purchase price of dry pumpkins ranges from €1.39 to 2.32/kg. The calculated expenses to produce 1 kg of dry pumpkin seed with direct seeding (treatments A and B) was calculated as €0.98 based on yields of 900 kg/ha. The expenses to produce 1 kg of pumpkin seed using transplants (treatment C) assuming yield of 1200 kg/ha was €1.20/kg. Note that the 30% higher yield in C treatment does not compensate for the additional expense of transplants. However, it may be possible to increase efficiency of transplant production by reducing costs.
Table 3. Pumpkin oil seed budget per hectarez.
|Type of expense||Production method|
|Unit/ha||Unit cost (€)||Total cost/ha (€)||Unit/ha||Unit cost (€)||Total cost/ha (€)|
|Fertilizer & fungicide||149.08||149.08|
|Harvest (combine)||3.3 hr||86.03||3.3 hr||86.03|
|Seed drying||900 kg||0.02||180.00||1200 kg||0.2||240.00|
|Mechanical service||23.6 hr||8.65||204.14||22.3 hr||8.65||192.89|
|Labor (net)||44 hr||2.32||102.31||41.5 hr||2.32||96.28|
|Breakeven expense||1 kg seed||€0.98/kgy||€1.20/kgx|
z1 km travel distance
yBased on 900 kg/ha yield
xBased on 1200 kg/ha yield