POPCORN VARIETIES (Su; approximately 110 days)

White, yellow, red, and black kernel types are available. Only white and yellow (small yellow and large yellow), are of commercial importance; yellow being the most important. Kernel size is generally recognized by the kernel count of 10 grams: Small (76-105); medium (68-75); large (52-67). Small kernel types are tenderer and are preferred for home use. Two popped kernel traits are recognized, butterfly and mushroom. Butterfly describes branched or irregular popcorn, usually more tender and free of hulls, but more fragile. Mushroom types are preferred by vendors of popped products. Buyers and processors will specify varieties. Commonly used varieties: White Cloud, Crookham 1084. For trial: Robust

ORNAMENTAL CORN VARIETIES (Su; approximately 100 days)

Chinook, Indian Ornamental, and Fiesta are standard size cobs; Wampum, Little Indian, and Strawberry Popcorn are small or miniature cob types.

ISOLATION

Popcorn and ornamental Indian corn should be considered as two additional, separate, isolation classes to be separated from all other isolation classes by 250 feet. (See ISOLATION in the file Sweet Corn for Processing.)

SEEDING

Due to its smaller plant size, popcorn is planted at slightly higher density than sweetcorn. Accurate spacing between plants is important because, due to its poorer stalk strength, excess crowding predisposes popcorn to lodging. Plant populations are between 20,000 and 30,000/acre, depending on variety and lodging susceptibility.

NITROGEN (N)

Popcorn N rates are lower than for sweet corn. Excess N predisposes plants to lodging. In the absence of research-based information for fertilization of popcorn, use 200 lb N/acre following a grain crop, 150 lb/acre following a vegetable crop or a poor crop of clover or alfalfa, and 100 lb/acre following a good crop of clover or alfalfa.

HARVESTING

Popcorn hybrids yield about 65%-70% that of dent corn. In research plots in the Hermiston area 10,000 to 11,000 lb/acre yields were measured in an extensive 1994 variety trial. Kernel yield is only one factor determining the suitability of a variety. Popping ratio (the ratio of popped kernels to total kernels), popping volume, pericarp characteristics, popped kernel texture, color and flavor are others. Mechanically-harvested popcorn should be harvested when kernels are between 16% and 18% moisture if a combine harvester is used. If ear-picked by a corn picker, moisture may be as high as 25%. When it is hand harvested, moisture can be as high as 30% provided that ears can be dried evenly to the necessary storage moisture of 13.5% to 14.5%. Drying too rapidly may cause kernel cracking. In commercial production, mechanical handling is minimized and moisture levels are strictly controlled to maintain popping volume and quality. Generally, popped corn that is "chewy" is too high in moisture, while that leaving too many unpopped kernels is probably too dry and should be conditioned. Other factors, especially mechanical damage, can affect popping quality.