Environmental requirements
[edit]Climate
P. ovata is a 119- to 130-day crop that responds well to cool, dry weather. In India, P. ovata is cultivated mainly in North Gujarat as a "Rabi" or post–rainy season crop (October to March). During this season, which follows the monsoons, average temperatures are in the range of 15–30 °C (59–86 °F), and moisture is deficient. Isabgol (P. ovata), which has a moderate water requirement, is given 5 to 6 light irrigations. A very important environmental requirement of this crop is clear, sunny and dry weather preceding harvest. High night temperature and cloudy wet weather close to harvest have a large negative impact on yield. Rainfall on the mature crop may result in shattering and therefore major field losses.
[edit]Soil
Isabgol grows best on light, well drained, sandy loams. The nutrient requirements of the crop are low. In North Gujarat, the soil tends to be low in nitrogen and phosphorus and high in potash with a pH between 7.2 and 7.9. Nitrogen trials under these conditions have shown a maximum seed yield response with the addition of 22 kg/hectare (20 lb/acre) of nitrogen.
[edit]Seed preparation and germination
P. ovata has small seeds; 1,000 seeds weigh less than 2 grams. Under ideal conditions of adequate moisture and low temperature 10 to 20 °C (50 to 68 °F), 30% of seeds germinate in 5 to 8 days. The seed shows some innate dormancy (3 months) following harvest. Attempts to eliminate this dormancy period by scarification, or by exposure to wet or dry heat, cold, ethylene, or carbon dioxide, are ineffective. Post-dormancy seeds show reliable germination in excess of 90% at 29 °C (84 °F), with lower rates of germination as temperature is increased.
[edit]Cultivation
The fields are generally irrigated prior to seeding to achieve ideal soil moisture, to enhance seed soil contact, and to avoid burying the seed too deeply as a result of later irrigations or rainfall. Maximum germination occurs at a seeding depth of 6 mm (1/4 in). Emerging seedlings are frost sensitive, therefore planting should be delayed until conditions are expected to remain frost free. Seed is broadcast at 5.5 to 8.25 kg/hectare (5 to 7.5 lb/acre) in India. In Arizona trials, seeding rates of 22 to 27.5 kg/ha (20 to 25 lb/acre) resulted in stands of 1 plant/25mm (1 inch) in 15 cm (6 inch) rows produced excellent yields. Weed control is normally achieved by one or two hand weedings early in the growing season. Control of weeds by pre-plant irrigation that germinates weed seeds followed by shallow tillage may be effective on fields with minimal weed pressure. Psyllium is a poor competitor with most weed species.
Plantago wilt "Fusarium oxyspirum" and downy mildew are the major diseases of Isabgol. White grubs and aphids are the major insect pests.
The flower spikes turn reddish brown at ripening, the lower leaves dry and the upper leaves yellow. The crop is harvested in the morning after the dew is gone to minimize shattering and field losses. In India, mature plants are cut 15 cm above the ground and then bound, left for a few days to dry, thrashed, and winnowing.
Harvested seed must be dried below 12% moisture to allow for cleaning, milling, and storage. Seed stored for future crops has shown a significant loss in viability after 2 years in storage.
[edit]Yield potential and performance results
The contract price for 95% purity psyllium husk set by the Indian Basic Chemical, Pharmaceutical and Cosmetic Export Promotion Council for April 1988 was $1.65/lb F.O.B. ($3.63/kg). This price is up from $1.14/lb ($2.51/kg) set in 1985. The average seed yield of P. ovata in India often exceeds 1 tonne/hectare (1000 lb/acre). Net yield of 95% purity husk after milling would be 275 kg/ha (250 lb/acre). Average gross revenue from milled product at 1988 prices would be $412/acre ($1030/ha). The costs of production and milling in the U.S. are unknown but would certainly need to be determined in order to analyze the potential profitability of a commercial psyllium venture.
[edit]Economics of production and markets
The U.S. currently imports and consumes approximately 8,000 tons of psyllium annually. A continued expansion of this market seems likely due to the high level of interest in natural dietary fibers. No variety has been tested in the Upper Midwest but it would seem that the varieties that are grown in India would not be suited to production in this area. A major cultural problem limiting psyllium production in this area is the shattering characteristic of the mature crop. Some success has been achieved by cross-breeding high yielding Indian varieties with varieties that are more shatter resistant. Until shatter resistant varieties are available, production of Isabgol is likely to be restricted to environments that consistently provide a cool dry harvest season.
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