पॉपकार्न : वि‍शेष प्रकार की मक्‍का उगाने की वि‍धि‍ 

Corn (Zea mays L.) is one of the important cereal crop in the world.  In India 49% of corn is used in poultry feed industry, 12% as animal feed and 25% as food in various forms. Diverse types of corns like sweet corn, dent corn, flint corn, pod corn,flour corn, waxy corn and pop corn are grown in India of which pop corn is the only corn that pops. Pop corn type is characterized by a very hard, corneous endosperm containing only a small portion of soft starch. Pop corn is essentially small-kernelled flint type. Pop corn has several grain colours are grown viz., white, yellow, red etc.

When kernels of popcorn are heated, they explode and produce large puffed flakes (popping). Once popped, pop corn has two basic shapes: one is snowflake or butterfly, which pops big and is shaped like a cumulus cloud and another is mushroom, which pops into a round ball.  Besides their use as a popular snack, ground pop corn, as flour or grits, can be used in the preparation of many traditional dishes.

Isolated planting is not necessary in case of pop corn, since there are no major xenia effects on popping expansion and many pop corns are cross-sterile with field corn. Although conditions for growing pop corn are the same as for dent corn, special harvesting, drying and storage practices are necessary to maintain popping quality.

Packaging and practices of pop corn:

Climate:

The climate requirements for cultivation aspects of pop corn are similar to that of dent corn. Pop corn requires considerable moisture and warmth from germination to flowering. The most suitable temperature for germination is 21°C and for growth 32°C. Extremely high temperature and low humidity during flowering period damage the foliage desiccate the pollen and interfere with proper pollination, resulting in poor grain formation. Pop corn growth requirements are similar to those for dent corn, with less adaptability to environmental extremes.

Soil:

Any type soil suitable for normal corn should produce a good pop corn. Soil pH should be in the range of 6.5 to 7.5 to get a good crop. Pop corn seeds germinate more slowly than dent corn, and the seedlings grow at slower rate. Thus, medium to coarse textured soils, which warm slightly faster than fine-textured soils, should improve germination, emergence and seedling establishment. The pop corn root system is less extensive than that of normal corn. Therefore, high clay soils and or poorly drained soils will weaken the roots, increase lodging and ultimately reduce corn yield.

Land Preparation:

Land preparation for popcorn is similar to that of normal corn. To ensure the optimum moisture for germination, pre-sowing irrigation should be applied. After reaching the field to tilth condition, two cross ploughings with disc plough and one ploughing with cultivator followed by planking were done for good seedbed preparation. If needed, a spike-tooth harrow or other finishing tools can be used with the last pass over the field to smooth the seedbed.

Sowing time:

Optimum time of sowing is depends on type of variety, weather condition, soil type and irrigation facility etc. However, most appropriate time of sowing is the last week of May to the first fortnight of July. Planting later than 15^th July often results in a reduction of yield. Early planting permits the crop to mature and reach the desired harvesting moisture of 15-18% by early to mid-October. Rabi sowing preferably is completed in between October end and middle of November so that the crop can establish itself before the onset of winter.

Seed and sowing method:

Seed rate for popcorn is lower than for normal corn because of its smaller kernel size. Seed was dibbled on the side of the ridges at a spacing of 15-20 cm keeping 3-4 cm seed depth. With irrigation facility the population should be from 80,000 to 83,000 plants/ha. A slightly lower population is used for dry land areas. Thus recommended seed rate of popcorn varieties is 12-14 kg/ha.

Seed treatment:

Before sowing of the pop corn, the kernel/seed should be treated with Imidacloprid @ 2g/kg seed, to avoid the insect attack.

Choice of varieties:

There are three types of pop corn kernels viz., white, yellow and red kernels. Generally white pop corn has a rice-shaped kernel and yellow pop corn kernels are pearl-shaped. Growers and processors should think about this when selecting a variety. In India there are mainly four released pop corn varieties (Table 1). However, all of them are medium in size and yellow and white pearl kernels types. These varieties can be grown across the country during kharif season, while in rabi they can predominantly be grown in peninsular India. Besides this another major consideration in pop corn variety selection is maturity because maximum popping potential of a variety can be achieved only if it reaches full maturity. If planting is delayed, consider an earlier maturing variety.

Table 1 Popular popcorn varieties in India

Fertility management:

Fertility requirements for pop corn are similar to normal corn. Fertilizer doses should be decided on the basis of soil test. In general the recommended doses of fertilizers are 120: 60: 40 kg/ha each of N, P₂O₅ and K₂O. In common the efficiency of nitrogen utilization during rabi season is better than kharif season. Nitrogen requirements are based on expected yield. The nitrogen should be applied into three split (¹/₃ each as basal, tassling and grain formation stage) doses. As pop corn seedlings grow slower than normal corn, a starter dose is more important than subsequent split doses. However, it must be kept in mind that high nitrogen rates can cause lodging, especially when less than the recommended rate of potash is used while, full dose of P₂O₅ and K₂O should be applied at the time of sowing with a uniform application of 25 kg/ha zinc sulphate once in three seasons.

Intercropping:

Pop corn being a snack items can successfully be cultivated in peri-urban areas in world wide. Though, instead of cultivating pop corn as sole crop it may be intercropped with other highly remunerative crops like cabbage, cauliflower, radish, spinach, coriander, potato, marigold, garlic, tuberose, gladiolus, spices and pea etc. It provides additional income to the farmers from unit area and makes agriculture more productive, profitable and sustainable.

Irrigation:

Irrigation of pop corn is the same as that for normal corns. Some growers like to delay early irrigation to stimulate better rooting of the developing plants. However, the value of this practice has not been determined. Irrigation during pollen shed is not recommended. Irrigation, should continue until the black-layer has formed in the developing kernels.

Weed Control:

Two hand-weeding are sufficient at 25 and 50 days stage after sowing to check weed growth. Tractor or bullock drawn cultivator is usually undertaken once at knee-high stage if weed situation requires. For chemical weed control, application of Atrazine or Simazine @ 1 kg a.i. per hectare at the time of sowing or before emergence of plants is used. This gives weed protection up to 30-35 days after sowing.

Insect and Disease Control:

Pop corn is more susceptible than field corn to diseases especially stalk rots and ear rots, and blue eye disease caused by three types of molds Penicillium viridicatum, P. cyclopium and Aspergillus glaucus. These pathogens not only affect the crop in the field but may also affect stored grains leads to low popping volume, low germination and sometimes a high level of toxicity. This disease is best controlled by proper aeration during storage. However, application of Bavistin @ 1 g a.i. per litre takes care of most of the foliar diseases.

Maturity:

Pop corn matures in 85-90 days in kharif and 95-105 days in rabi. Since kernels are the monetary product, harvest should necessarily be done on the attainment of physiological maturity, which is evidenced by the formation of a black polyphenol layer at the base of the kernels. For optimum popping expansion the pop corn should be dried to 14-15% grain moisture. The harvested and shelled pop corn is stored in moisture-proof sealed containers.

Harvesting and Storage:

Either ear or shelled popcorn may be harvested. Moisture at harvesting for ear corn should be 18-20% and for shelled corn 16-18%. Harvesting equipment should be adjusted accurately and carefully so that kernel damage is prevented. Damaged kernels do not pop properly and will cause a discount on the grain market. Depending on the proximity of the processing plant, the grain may be delivered directly at harvest or stored on the farm until delivery is requested. If on-farm storage is required, storage facilities must be clean and good aeration must be provided. Aeration is essential for extended storage. Generally, the delivery of the grain is taken at 14-15% moisture, so the storage and aeration facilities must be able to remove some grain moisture. Relative humidity of 70% will maintain the grain at the proper moisture. Kernels that are too dry will not pop properly. Dirt, cob remnants and other foreign material at harvest must be cleaned before storage. Proper moisture level is the reason to store pop corn properly. For day-to-day use pop corns are to be stored in airtight container and in cool cupboard. Pop corn should not be stored in refrigerator. Air inside a refrigerator contains very little moisture and can cause the pop corn to dry out.

Marketing:

Pop corn is mainly produced under contract farming, which specifies the varieties and the acreages to be planted. The grower usually buys the seed through the contracting company. Pop corn seed grown without sales contract is difficult to market and is risky for farmers who do not have appropriate storage facility with good aeration.

Popping Quality:

The quality of pop corn is expressed as popped volume, shape of the popped kernels, tenderness, and flavour. Only volume can be measured easily. The popped volume is perhaps most important because the commercial buyers buy on weight basis but sell the popped pop corn by volume. The conventional oil popping methods are still most common. However, air popping and microwave popping are becoming increasingly important in the retail market. Popping expansion of the commercially occupied pop corn varieties in USA is 40: 1, while that in India is just 20: 1. Problems associated with low expansion volume, the high number of unpopped kernels and scorching of popped kernels make conventional popping superior to microwave popping. Popcorn variety, the moisture content of the kernels, storage conditions, type of package, and microwave oven wattage influence the quality of microwave popping.

Value Addition:

Pop corn while being popped can be coated with salt or sugar or cheese. Sometimes coating with chocolate, enhances the market value and consumer acceptance. The manufacturers prefer butterfly type of popping due to increased volume since pop corn after popping is sold on a volume basis. But consumers prefer mushroom types.

Future Strategies for Pop corn in India

Till date in India no hybrid of pop corn is available. Thus the produce has less uniformity, which in turn affects their market acceptance, particularly in international market. Therefore, there is a need to develop pop corn hybrids in India. Second problem associated with Indian pop corn cultivars is less popping ratio. Best pop corn variety has popping ratio of 20: 1 as against 40: 1 in USA and they group in medium size only. Thus there is scope to breed for pop corn cultivars with enhanced popping ratio and with soft texture and bigger volume. During breeding, scheme selection is to be made towards kernels with thick pericarp, hard coating with soft starch cavity inside. For this purpose efforts may be made in screening of germplasm and their utilization in breeding schemes. Popping ratio of pop corn is very much dependent on storage as well as popping temperature and moisture. Therefore, appropriate drying and storage of pop corn grains are very much essential. In USA and other developed countries food industries are involved in packaging pop corn with appropriate oil, butter and salts in popping bags. These bags are ready to pop in microwave. As a result such packings are very handy for end users and they fetch very good market price. Such entrepreneurship is very much essential in India. This is possible only with support from food industry and policy makers.

Authors:

B. P. Meena, V. D. Meena and M. L. Dotaniya

Indian Institute of Soil Science,

Nabi Bagh, Berasia, Road, Bhopal-462 038

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