CORN
Introduction
Corn ranks second to rice, not only in terms of area devoted to its production but it has been a staple food of about 20% of the total population of the Filipinos. Aside from this, the green corn, boiled or roasted, is a popular snack food and may also be cooked a vegetable or soup. Other by-products of corn include corn flour and syrup, sugar and oil. In terms of nutritive value, corn is richer source of vitamin A than polished rice. It contains high amounts of minerals such as calcium and phosphorous. Moreover, it is also a source of starch derivatives for oil, fibers and other industrial uses.
Corn has also been used as an important ingredients in animal feeds. Corn may be planted anytime of the year provided there is adequate soil moisture. However, it is best to plant from May to June during the wet season and from October to November during the dry season.
Recommended Varieties
Seed Selection
Select varieties that are high yielding, early maturing, tolerant to pests and diseases, and adopted to the climatic conditions of the area.
Some parameters of a good seed:
- High purity in terms of cultivars and species
- High viability or high percentage of germination
- High vigor-vigorous under wide condition
- Non-lodging
Land Preparation
Prepare a well-pulverized field for uniform germination and good root development. Plow at a depth of 15-20 centimeters when soil moisture is right. That is, when soil particles 15 cm below the surface separate and only thin portion sticks to the finger but no ball is formed. Harrow twice with 2-3 passings to break the clods.
If a disc plow is used, plow under corn stubbles at a depth of 18-20 cm. The use of dusc plow enables a farmer to utilize corn stubbles as additional source of fertilizer. Clayey and weedy fields require tow or more plowings and several harrowings.
Crop Establishment
Planting
To attain an optimum plant population density of 50,000 - 60,000 about 16-18 kilograms (kg) of hybrid seeds or 18-20 Open Pollinated Variety hybrid seeds per hectare is needed. Space the furrows with 75 cm interval/ Plant sees about 3-5 cm deep when the soil moisture is just right for planting, then cover the seeds with soil.
Thin seedlings to one plant per hill about 7-10 days after emergence.
Success in corn production depends on proper care and maintenance of the crop throughout its life cycle. Refer to the Management Guide for the Various Growth Stages of the Corn Plant.
Cultivation
Cultivation improves soil tilts and control weeds. Off-bar between furrows to aerate medium-textured or heavy soils 22-25 days after planting. Hilling-up 27-30 days after planting or just after side dressing the remaining recommended amount of nitrogen.
If the field is weedy, use an inter-row cultivator (paragut) or employ line weeding.
Nutrient Management
The rate of fertilizer should be based on the results of soil nutrient analysis. Soil samples may be submitted at the Municipal Agriculturist Office in the area or at the regional soils laboratory. Negotiate with the agricultural technologist in the area to determine the general fertilizer recommendation.
Otherwise, use 4 bags of complete fertilizer (14-14-14) per hectare as basal application in the furrows and cover the fertilizer with a thin layer of soil, about 2 cm thick. After 25-30 days of planting, side dress with 4 bags of ammonium sulfate or 2 bags of urea. Cover the fertilizer immediately by shallow hilling up.
During wet season, split application of nitrogen (N) fertilizer is recommended. Apply all the needed phosphorous and potassium and half of the recommended amount of N in the furrows before planting. Side dress the other half of N at least 4-5 cm away from the base of the plant 20-24 days after emergence or immediately before hilling-up when there is a right soil moisture. To attain higher yields apply animal manures and crop residues just before land preparation.
Due to the possibility of drought during the dry season, apply all the recommended amount of fertilizer in the furrows just before planting to provide all the needed nutrients to the plants. However, if supplemental irrigation is available, follow the application of fertilizer for the wet season. Cover the fertilizer with 2-4 cm soil to prevent seed injury. Organic fertilizer or compost may be applies in addition to the recommended inorganic fertilizer.
Water Management
Insufficient or excessive soil moisture is a limiting factor in corn production. Excess in the rootzone within 36 hours injures the plants.
Insufficient soil moisture during reproductive stage decreases yield from 20-30 percent. When there is no adequate moisture during tasseling stage, irrigate the cornfield by "flush irrigation" if available.
Overhead or sprinkle irrigation may also be sued in elevated or sandy loam soil. In flat rolling furrow irrigation is advisable.
Weed Management
To optimize yield control weeds during the critical period - at 28-35 days after planting, should be removed. After this period, weeds may no longer reduce yield significantly.
Weeds can be effectively controlled by combination of two or more practices. It depends on weed species present, availability and comparative cost of control to be employed.
Some of the common weed control are:
- Physical control
- Thorough land preparation
(Off-barring 17022 days after planting can control weeds and loosen the soil. Hilling up to 25 to 30 days after planting also reduce weed population.) - Inter-row cultivation
- Hand weeding
(or line weeding is recommended if necessary) - Or a combination.
(Weeds can also be eliminated by cultivation before planting. Remove weed seeds before they produce seeds to reduce sources of weed seeds in the succeeding cropping season.) - Chemical Control
- This can be employed through the use of selective and non-selective herbicides. Non-selective herbicides kill all vegetation they may come in contact with. Apply this kind of herbicides before crop emergence or immediately after planting or spraying between planted furrows.
- Pre-emergence herbicides are effective against grasses and to some extent sedges and broad leaf weeds. However, it is not advisable to walk or roam around the sprayed area because weeds will grow on the footprints.
- Apply post emergence herbicides when both the crop and weeds have already emerged.
Pest Management
- Corn Borer (Asiatic Corn Borer)
Scientific Name: Ostrinia furnacalis (Guenee)
Local Names: Dalipog (Ilocano); Amasok or Tibgoy (Bicol/Ilonggo); Tuhob (Cebuano) - Eggs are flat, creamy, shiny and laid in mass (about 25-50 eggs/egg mass) in fish scale-like arrangement on both sides of the corn leaves. Incubation period is 4-5 days.
- Newly hatched larvae are pinkish with black or brown heads. Later instars are creamy and brownish-yellow. It molts five times from 12-13 days.
- The pupa is dark red and the pupal period is about 5-12 days,
- Total development period from egg to adult emergence ranges from 27-52 days.
- The adult is yellowish brown moth with waxy dark lines on wings with an expansion of about 35 mm.
- Pinhole lines lesions on leaves caused by first instar larvae.
- Match head-size holes and elongated lesions on leaves and leaf sheaths caused by second and third instar larvae.
- Broken stalks and leaves.
- Premature drying of whole plant and ear
- Early and synchronous planting in contiguous areas using resistant varieties
- Manual picking/crushing of eggs masses and larvae while inspecting the plants
- Detasseling of clumped tassels one to two days after emergence or detasseling three rows out of four rows of corn plants
- Trichogramma parasites at 33-35 days after planting (after hilling-up) at 3-4 days intervals.
- Crop rotation coupled with weeds elimination.
- White Grub (June Beetle)
Scientific Name: Leucopholis irrotata L.
Local Names:
Larva- Buc-an (panay/Visayan); Ulalo (Tagalog); Abaling (Ilocano); Aruwag (ibanag); Burlod (Cebuano)
Adult - Kalibobog (Bicol); Buod (Bohol); Bakukang (Cebuano); Afang (GAddang); Asimuwa (Ibanag); Aros-aros or Abal-abal (Ilocano); Dahueng (Negros Oriental); Salibubang (Kapampangan); Labog-labog(Panay/Visayan); Organo (Surigao/Agusan); Salagubang (Tagalog); Batungol (Waray) - The larval stage of the June beetle (simmawa or abal-abal) is fleshy, wrinkled and normally curved. It is white when newly hatched but turns light brown.
- The full grown larva is pale yellow with blackish abdominal portion due to intestinal contents seen through transparent skin. The dorsal part is covered bu stout brownish and thickly setae. These are longer, weaker and fewer at the ventral surface along the sides of the body. The whole larval period lasts from 252 - 336 days.
- Larvae eats the roots of the corn plant
- Irregular patches of stunted plant, yellowing or wilting plants
- Prepare land thoroughly before planting
- Practice deep plowing in areas inspected to have chronic grub infestation
- Seed treatment with chemicals
- Incorporate corn stubbles (composted) in the soil for white grub to eat instead of the corn plant.
- Corn Seedling Maggot
Scientific Name: Atherigona oriyzae (Malloch)
Local Names:
Larva - Apihis (Cebuano)
Adult - Bangaw (bicol); Ngilaw (Ilocano); Langaw (Ibanag) - Eggs are elongated, peral-white turning dark when about to hatch, anterior and roundish, slightly curved and laid singly on the outer surface of the leaves. Incubation period is 2-3 days.
- Newly hatched larvae are creamy white to transparent, elongated and taper towards the head end, becoming dark yellow in the last instar. Larvae undergo three instars from 8-18 days.
- The pupa is ovoid and light to dark brown. Pupal period is 5-11 days
- The adults are greenish-black with three blackish stripes on the back of the thorax and three pairs of black spots on the last abdominal segments.
- Leaf feeding lesions, curling and breaking of young leaves
- Wilting, drying and rotting of central shoot
- Infested seedlings show stunted growth and later may produce side tillers
- Synchronous planting in contiguous areas
- Early planting in the growing season to escape high maggot population
- Clean culture including the removal of alternate host plants
- Seed treatment with thiodicarb or carbofuran ST before planting
- Common Cutworms
Scientific Name: Spodoptera litura
Local Names: Ulod (Ilonggo, Bicol); Arabas (Ilocano) - Eggs are round and pale white and laid in mass on leaves or objects on the ground covered with yellowish-brown hairs. Incubation period is 3-5 days
- Young larva is greenish with black band one-third of the length from head and a full-grown larva (developed from 20030 days) is green with bright yellow dorsal lone and lateral stripes with black spots.
- The pupa is reddish brown and about 1.6 cm long. The pupation period in soil is from 6-10 days
- The adult is about 20-25 mm long with wings (forewings are purplish-brown with numerous lines and spots and hind wings are whitish with narrow band along the center margins).
- Scrapping of leaf tissues by young larvae, leaving irregular grayish white patches on the leaves
- Older larvae may cut stems and leaves, including veins and midribs
- Young plants may be completely defoliated by older larvae (third to sixth instars)
- Plow fields to remove weeds which may serve as alternate hosts.
- Collect egg masses and crush them
- Make small trenches around the field and put some cut grasses for shade. Collect hiding larvae during early morning
- Chemical spraying if severe infestation (use pyrethroids)
- Corn Semilooper
Scientific Name: Chrysodeixis chalcites
Local Names: Dangan-dangan (Ilocano); Dangaw (Ibanag); Dangaw-dangaw (Cebuano) - Eggs are pearl, white and spherical laid singly on leaves. Incubation period is 3 days
- Larvae are greenish with lighter dorsal and lateral stripes and about 50 mm long. They have modes with lopping motion.
- The pupa is light green then turns reddish brown later. The pupation period takes place either in silver cocoon on lower leaf surface or in the soil and lasts for 7 days.
- The adult is brownish with golden bronze Y-shaped mark and white spot on outer wings.
- Elongated lesions o shedding of leaves due to feedings on soft leaf tissues but sparing the veins and midrib
- Corn silks are cut during silking stage
- Synchronous planting in contiguous areas.
- Armyworms
Scientific Name:
Black Armyworm - Spodoptera exempta Walker (BAW)
Grass Armyworm - Spodoptera mauritia Basidural (GAW)
True Armyworm - Mythimna separate Walker (TAW)
Local Names: Uod sa humay/Amigba (cebuano); Igges ti bunubon/Arabas (Ilocano); Balulo (Misamis Oriental); Ulad gueng punlang pale (Kapampangan); Tagus-tus (Panay/Visayan); Uod ng punlang palay (Tagalog)
Description:
Plant growth stages affected: Seedling to maturity
Damage:
Control Measure:
Description:
Plant Growth stages affected: Emergence to seedling stage (especially during heavy infestation)
Damage:
Control Measure:
Description:
Plant growth stages affected: emergence to early whorl
Damage:
Control Measure:
Description:
Plant growth stages affected: Emergence to Early Whorl
Damage:
Control Measure:
Description:
Plant growth stages; Emergence (one leaf stage) top silking
Damage:
Control Measure:
Description:
| Black Armyworm | Grass Armyworm | True Armyworm |
| Eggs | ||
| • Pearly pale yellow | • Yellow | • Smooth. Shining and milky white • Spherical |
• Subglobular and slightly flattened; laid in mass on leaves and covered with buff-colored hairs. • An egg mass contains 200-450 eggs which can be hatched in 3-5 days |
||
| Larvae | ||
| • Generally black • Head is faintly mottled with dark brown spots, light yellow meridian line on the back • Narrow stripes on the side |
• Light or dark brown with pale stripes on each side along the back | • Greenish or purplish-brown on the back but pale neutrally • Above and beneath the |
Management Guide for Various Growth Stages of Corn
The time of emergence at any of the critical growth stages of corn can be predicted in normally growing plants, based on the number of expanded leaves before flowering, the appearance of the reproductive organs and the kernel development.
The maturity stages start after the silking phase is about 115 days after emergence.
Growth Stages
- Emergence
- Leaf Stage
- Fourth Stage
- Sixth Leaf Stage
After sowing and under favorable conditions, the seeds swell and the embryo enlarges. The coleorhiza enclosing the radicle emerges first. The radicle elongates rapidly followed by the plumule.
About two to five seminal roots emerge at the base of the plumule. These roots and the radicle constitute the primary root of the young seedling. The first internode formed elongates to raise the plumule towards the surface of the ground. As soon as the coleoptile which encloses the plumule is exposed to light, it burst and two leaves emerge.
Adventitious roots develop at the node just below the surface of the ground. These become the permanent root system if the plant. Regardless of the depth of planting, the permanent roots develop only a few centimeters below the ground surface. The first internode between the seminal and permanent roots (mesocotyle) normally elongates to not more than five inches.
Management guide
Depth of planting influences the length of time from planting to emergence. Seedlings from deep planted seeds have a greater depth of soil to penetrate. In addition, the temperature is cooler at greater depths and growth is slower.
Nutrients and food reserves in the seed generally supply the young plant adequately prior to emergence. Place the fertilizer in band to the side and slightly below the seed to allow the primary roots to easily get in contact with the fertilizer. Fertilizer placed too near the seed can result in salt injury to the young plant.
The emergence of two leaves marks the beginning of a new mode of growth of the plant. The roots at the base of the first two leaves elongate but have but yet branched or formed root hairs. However, the primary roots have many branches and root hairs.
Management guide
Since the roots are relatively small, higher concentration of fertilizer nutrients is needed to stimulate early plant growth. However, the amount of nutrients required is relatively small. The fertilizer is effectively absorbed at this stage if placed in band where the primary roots get in contact with it. Roots are not attracted to this fertilizer band, so that the fertilizer must be placed where the root. It takes about a week from plant emergence to this stage.
At this stage, roots of the first node branch develop root hairs. The primary roots grow very little, and usually die but new roots at the second node elongate. The tassel is initiated at the tip of the stem, but it is still below the soil surface. All the leaves and ear shoots have initiated.
Management guide
Cultivating too near the plant after this stage destroys some of the permanent roots, Exposed leaves may be damaged but the plants may outgrow the damaged parts with minimal reduction in yield.
The permanent roots of the first and second nodes are extensive and well-branched while new roots are elongating at the third node. The internodes of the fifth, sixth and ear shoots have been initiated and the growing point levels with the ground surface.
Management guide
Since the nodal root system is now well-distributed in the soulm precise placement of fertilizer is less critical. However, the plant node begins to absorb greater amount of nutrients. Fertilizers should be applied in adequate amount to supply deficient nutrients in the soil.
Root worms may destroy the developing nodal roots and thereby restrict plant growth. Later, root development at higher nodes may result in plant recovery.