Wheat Production

Based from the literature, wheat was originally a wild grass which first grew in Mesopotamia, in the Tigris and Euphrates river valleys (middle east) nearly 10,000 years ago. Evidence shows that it has been a major agricultural commodity since the prehistoric times and played an important role in the development of civilization.

As early as 6700 B.C. Swiss lake dwellers use it in flat cakes but it was the Egyptians who discovered how to make yeast-leavened breads between 2,000 and 3,000 B.C. Since wheat is the only grain with enough gluten content to make a raised loaf of bread, wheat quickly became favored over the other grains. Early explorers and merchants introduced wheat into Europe and colonists brought it to North America early in the 17^th century. In the US, wheat production started in Massachusetts and moved westward with settlers during next 200 years.

Archaeologists found carbonized grains of wheat in Pakistan and Turkey, in the tombs of Egypt and in storage vessels in other countries.

Wheat, Triticum aestivum evolved through the inter-crossing of at least 3 related wild ancestors. A proposal said that a tetraploid Emmer evolved from a wild type (Triticum dicoccoides) that carrries the A and B genomes. Mutations of Emmer resulted in other tetraploids- durum, poulard and polish wheat. Emmer eventually crossed naturally with Triticum taeeshii (Aegilops squarrosa ) diploid with the D genome, to produce the hexaploid spelt, with ABD genomes, spelt later mutated to common wheat (Triticum aestivum ) which in turn, mutated to produce club and shot wheat.

I. BOTANICAL CHARACTERISTICS

Wheat belongs to the grass tribe Hordeae and in the genus Triticum. An annual or winter annual grass with a single spikelet per node of the rachis and 3 or more florets per spikelet with at least one being sterile in most cases.

Wheat spike is indeterminate in growth, does not terminate with a spikelet. A spikelet is composed of 2 broad glumes and one or several florets. A floret consists of a lemma, palea and caryopsis. The awn arises dorsally on the tip of the lemma in awned sorts. The caryopsis or grain has a deep furrow and a hairy tip or brush. Color of the grain may be amber, red, purple or creamy white. Glumes in wheat are fairly large and may have an awn. In vegetative stage, like other cereals, wheat is narrow-leaved except for corn and sorghum, have neither ligule nor conspicuous auricles. The first internode in wheat seedlings elongates very little, thus the secondary roots form essentially where the seed is planted which differ it from other cereal seedlings.. The extent of elongation of the coleoptilar internode is genetically determined and varies among cultivars of winter wheat.

The plant normally produce 2 or 3 tillers under typical crowded field conditions but individual plants on fertile soil with ample space may produce as many as 25-30 grains in 14-17 spikelet. Large spikes may have 50-75 grains. The shape of individual kernel depends upon the degree of crowding within a spikelet. The spikelets at the base and tip of the spike usually contain small kernels. Within the spikelet, the second grain from the base usually is the largest and first grain is next in size but when present the third, fourth and fifth grains are progressively smaller. Pound of wheat may contain 8,000-24,000 kernels. A bushel of common wheat averages 700,000-1,000,000 grams. The legal weight of a bushel of wheat in legal transactions is 60lbs. but the average test weight is about 58lbs. The maximum test weight is about 67lbs. And the minimum is about 40lbs per bushel. The typical wheat kernel is from 3-10mm in length and from 3-5mm in diameter. Consist of the germ, about 2.5% (embryo, consisting of plumule, scutetlum, radicle and hypocotyls), high in protein and fats and is removed before miling; bran, 14% (pericarp, testa, nucellus and aleurone layer), by product of milling and is used in dairy and poultry feeds. And the starchy endosperm comprises from 83-87% (storage part of caryopsis that develop from the union of polar nuclei with the endosperm nucleus).

II. CHEMICAL COMPOSITION The approximate chemical composition of the wheat kernel is starch, 63-71%; protein, 10-15%; water, 8-17%; cellulose, 2-3%; fat, 1.5-2%; sugar, 2-3%; and mineral matter, 1.5-2%. Protein content of wheat varies in different regions.

Hard wheat flour usually have a higher ash content than do soft wheat flours. The environment, chiefly weather condition also affects the ash content of wheat and the resultant flour. The chief constituents of wheat ash are oxygen, phosphorus, potassium, magnesium, sulfur and calcium.

The hard red spring and hard red winter wheat contain an average of about 11-15% protein when grown in the great plains and northern prairie states. Soft wheat contain 8-11% protein when grown in humid areas..

The preferred protein percentages in wheat for various domestic purposes are about as follows: macaroni and noodles, 12.5-15; white bread, 11-14; all purpose flour, 9.5-12; crackers, 9.5-11; pie crust and donuts, 8-10.5; cookies, 8-9.5; cake, 8-9.5. Gluten of the wheat kernel contains about 17.6% nitrogen. The percentage of nitrogen determined by analysis is multiplied by 5-7 to determine the protein content. The protein of most feed crops contains about 16% N and the factor 0.25 is used.

III. SPECIES AND CLASSES

Some species of wheat are Triticum monoccocum, Triticum turgidum L., Triticum timopheevi , Zhuk and Triticum aestivum .

CLASSES:

1. HARD RED SPRING - grown in North Central States, mostly where the winter are too severe for the production of winter wheat.

2. DURUM WHEAT - produced also where hard red spring is grown but the chief section lies west of the Red River Valley in North Dakota, small acreages of durum were grown in the making of semolina from which macaroni, spaghetti grown extensively in North Africa, Southern Europe and Soviet Union.

3. HARD RED WINTER WHEAT - adapted esp. to the central and southern Great Plains where the annual rainfall is less than 35 inches.

4. SOFT RED WINTER WHEAT - grown principally in the Eastern States. They are softer in texture and lower in protein than the hard wheat. They are generally manufactured into cake, biscuit, cracker, pastry, and family flours.

5. WHITE WHEAT - grown in the Far Western states and in the Northeastern states. Largest acreages are in Washington. Used principally for pastry flour and shredded and puffed breakfast foods.

MIXED EMMER, SPELT, EINKORN, POLISH AND POULARD- are not considered wheat in the official grade.

 

IV. ADAPTATION OR ENVIRONMENTAL REQUIREMENTS

In the Northern Hemisphere, winter wheat is planted in the early fall when the soil temperature drops below 55⁰F (13⁰C). It tillers, elongates and then flowers in late spring or early summer and ripens in June, July or August. It requires vernalization, exposure to a prolonged, cold period during seedling stage to induce flowering. Cold temperature favor initiation of tillering. if planted in the spring, auxin- regulated phenomenon occur. Losses are intensified by low temperature and wind. It is damage if temperature falls below 32⁰F, freezing temperature causes stamen and pistil malformation and pollen sterility.

Spring wheat, is sown in early spring, germinates, grows and ripens during spring and summer, harvested in early fall or late summer. Planted after the soil temperature rises above 34⁰F and it can grow at near freezing. Early planting is desirable to insure maximum growing season.

All wheat grows best on loamy soils that are medium in texture, fairly high in organic matter and fertile. Wheat is not well adapted to acidic soils; most favorable pH range is from 7.0-8.5. It requires 10-25 inches (25.4-63.5) of annual precipitation distributed throughout its growing season. Wheat cannot germinate in dry soil. Any condition that reduces root growth of weak seedlings. Moisture stress reduces tillers per plant and thus reduces yield. Stress during flowering cause pollen sterility.

In summary, wheat does not produce well in warm, humid areas. It requires moderately cool conditions for germination followed by cooler period for tiller formation grain matures best under warm, dry condition that are also ideal for harvesting the cro.

V. CROP MANAGEMENT TECHNOLOGIES

A. SEEDBED PREPARATION

Similar to other cereals, except corn, fields are first cultivated with a moldboard plow or disc to a depth of 4-12 inches (10-30cm). The exact depth depends on the location and cropping history of each field. It is desirable to change plowing depth periodically to prevent the development of a compact plowsole or hard pan immediately below the plowing depth. The initial plowing spreads stubble over the surface of the soil to insure protection from wind and water erosion and to trap snow and thus foster water accumulation and storage. This type is referred as stubble mulching or trashy fallow. Plowing is followed by harrowing immediately before planting. Folds maybe chiseled periodically to loosen the subsoil. Noble blade is used in dry areas.

For spring wheat, an initial cultivation maybe made in the fall, after harvest. For winter wheat, it is desirable to prepare the seedbed as early as possible (July & August). Early seedbed preparation with cultivation immediately before planting is effective in controlling fall germinating annual weeds such as grass, it also allows time for organic matter to decompose and may enhance infiltration.

Seedbed must contain the proper balance of all necessary minerals, preparation should insure adequately moist soil within 2 inches (5cm) of the soil surface, the seedbed should be fine enough to minimize water loss and allow seed soil contact. Remember, seedbed must not be over cultivated.

With low levels of mechanization available, seedbed has proved difficult and time consuming in most facilities.

B. ROTATION

In eastern states where winter wheat often is seeded on corn stubble, rotations is likely to contain at least one legume and one or more cultivated crops. In the corn belt an efficient rotation for much of the area is winter wheat. After the wheat harvest, the lespedeza may be permitted to produce a crop of hay. A common rotation is corn, wheat, lespedeza for pasture, hay or seed, wheat. In cotton belt, wheat often cannot be sown immediately after cotton because of the late maturity of the latter crop. A rotation satisfactory for this area is wheat, followed by soybeans or cowpeas for hay or seed; well-fertilized cotton, with vetch or Austrian winter peas planted between the rows for green manure, corn, stalks cut and removed from the field.

For Kansas, a popular rotation for the Northeastern part of the State is clover, corn, oats and wheat. Red clover or sweet clover is seeded with the wheat to be grown for hay or seed the next year, making a five-year rotation. In central Kansas are those that contain alfalfa. Because of subsoil moisture depletion by alfalfa, the crop that follows, it must be bale to endure drought. A satisfactory rotation is alfalfa (2 or 3 yrs), sorghum, corn, oats, wheat. In Western Kansas, rotation is grain sorghum, fallow, wheat fallows, fallow. A suggested rotation is grain sorghum, fallow, wheat (2-3yrs) continuous winter wheat with mulch tillage has produced good yield in some areas where weeds and alternate winter wheat and fallow are a practical sequence where the annual precipitation is less than about 22-24 inches in the southern great plains, 18-20 inches in Central Great Plains, and 14-16 inches in the Northern great plains as well as in the intermountain region. A wheat-pea rotation is profitable in parts of the Columbia Basin where the annual precipitaion as 15-22 inches. Spring wheat follows an inter tilled crop such as corn, potatoes or sugar beets most advantageously in the Northern spring wheat region. Green manure crops in preparation for wheat have been unprofitable in semiarid regions.

C. PLANTING

American wheat crop is sown with a drill. Drills with disk furrow openers are used most generally in the humid regions. Hoe drills are popular in the semiarid sections of the Pacific Northwest on clean fallowed land. This type of furrow opener turns up clods and does little pulverizing and this is helpful in preventing soil blowing. Furrow drill has been widely used in the semiarid Western Great Plains where winters are server. It is a partial insurance against winter killing and soil blowing and it places the seed deep enough to reach moist soil sowing no-till fields or those covered with a thick stubble mulch requires drills with disk or blade cutters to penetrate the residues.

Seedling depth for wheat varies from 1-3 inches (2.5-6.7 cm) depending on the type of soil, seed size and the level at which adequate moisture is available for germination. It is desirable to plant into moist soil but not if the planting depth exceeds about 3 inches. Seedling deeper than 1-2 inches is advantageous only in permitting germination to occur and roots to develop before the surface soil dries out, seeding wheat at a depth of 1inch or less causes the crown to form just above the seed and deeper than 1 1/2 inches (except where necessarily to insure prompt germination) merely uses up part of the energy in the seed in producing an excessively long sprout, delays and weakens the seedling accordingly.

Wheat is sown from October to December depending on the farming system. In Cagayan Valley of Luzon, Philipines (Tuguegarao), the peak rainfall is in November normally in the form of typhoons which typically delay rice harvest and the subsequent seeding of the wheat crop. Wheat in the past few seasons has normally been sown in late December.

Medium-season seeding of winter wheat for any locality is usually most favorable. Wheat sown late generally suffer more winter injury, tiller less and may ripen later the next season. Wheat sown too early may use up soil moisture, joint in the fall, suffer from winter injury and foot rots and become infested with the Hessian fly. The chief disadvantage of too early seeding of winter wheat is the likelihood of injury from foot-rot diseases that develop under warm conditions. The safe date is the earliest date at which wheat can be seeded to escape damage from this insect. Wheat should generally be seeded 7-10 days earlier than the safe date when Hessian fly is not present. This gives the plants a better start in the fall. When wheat is sown during an extremely early mild period that is followed by a cold snap, the wheat remains in the ground and emerges during subsequent warmer weather usually without evidence of having been injured.

Rate

Planting rates depend principally on predicted available moisture. In semiarid regions that have only 10-20 inches (25u-30.5u) of rain per year, seeding rate may be as low as 20lbs of seed/acre (22.4kg/ha). All seeding rates should be based on a pure live seed rating. Areas that have high annual precipitation plain rates can be 100lbs per live seed rating. Areas that have high annual precipitation plain rates can be 100lbs per acre (112kg/ha). With higher planting rates, row spacing may be as narrow as 4 inches (10.2 cm), with lower planting rates. Rows are planted from 12-18 inches (30.5-45.7 cm) apart. Row spacing on commercial grain drills range from 7-9inches (17.8-22.9 cm)

D. FERTILIZER

Research into NPK requirements for wheat has been quite extensive in Thailand and Philippines. Responses to P have been rare. Banding of P with the seed has shown to be more efficient than incorporation before planting indigenous rock phosphate applied at equivalent rates of available phosphorus produced produced yield not significantly different to triple super phosphate in the following year. There have been no significant responses to potassium.

With the N fertilizer a fairly consistent picture has emerged under irrigated conditions, a straight line response to N is obtained, usually up to 100-120kg N/ha with seeds/ spike normally about 7kg/N. The response to nitrogen is markedly affected by seeding date.

In no instance has the splitting of N resulted in increased yield. In fact, in recent work in the Philippine all fertilizer NPK applied at the first irrigation resulted in yield slightly higher than basal or split application and significantly increased the number of spikes/m². No significant differences have yet been found below N sources.

For commercial production, median application are recommended. In the absence of consistent responses to phosphorus and potassium, 60kg N/ha for irrigated with 30kg for rainfed conditions are the general recommendations.

Specific fertilizer recommendations should be based on the results of soil tests. In general, yield of a plant is reduced if the plant is deficient in any element at any time during its life cycle, even though the deficiency is alleviated by the application of fertilizer. The earlier the deficiencies is corrected, the less yield will be reduced.

E. IRRIGATION

Irrigation management must aim to avoid waterlogging, particularly during the establishment phase were possible, irrigation is recommended although this is not practical in the heavier soils in Thailand with the present technology. Research is currently under way to investigate bed site and shape to avoid prolonged water logging. Many of the soil form and crust before the wheat emerges. This can be partially overcome by increasing the seed rate to increase pressure on the crust. However, it remains a substantial problem necessitating high labor inputs to maintain a moist surface until emergence. After establishment, the stage most sensitive to drought stress is around anthesis.

PEST MANAGEMENT

1. DISEASE CONTROL

As the current levels of genetic resistance to tropical diseases are low, some measure of control must be attempted by crop management. In the Philippines, a wide range of chemicals has been tested as seed treatment against the soil-borne disease complex (Sclerotium rolfsii, Rhizoctonia solani, Fusarium roseum, and Helminthosporium sativum ). Field studies under low disease pressure indicate that both propiconazol and mancozeb partially controlled Helminthosporium sativum when applied at 50 days after sowing with the former being more effective. However, propiconazol if not available in the Philippines, mancozeb is recommended. Under high inoculum load, it is totally unsatisfactory. An additional problem with helminthosporium control. It has been noted that wider row spacing reduced disease severity. Nitrogen application may restricted in high disease incidence areas in order to avoid excessive vegetative growth by which high humidity is maintained within the crop. In addition, some farmers are convinced that the use of NPK fertilizer reduces the severity of the disease.

2. WEED CONTROL

The predominant weeds in the wheat target areas are various species of Echinochloa Eleusine and Digitaria for grassy weeds, with Amaranthus spp. Portulaca oleracea and Trianthema portulacastrum the main broadleaf weeds. Volunteer rice can also be a problem. The lower yield of wheat currently attained in rainfed conditions preclude intensive weed control measures, where some supplementary irrigation is available, the increased yield potential should encourage more thorough weed control. An experimental data show that weed control is essential in the first 4-5 weeks. If the crop is kept weed free during that period, yield are as high as those from crops kept continuously weed free. Quite low populations, particularly of grassy weeds, reduce yield.

Mechanical aids to weeding hand weeders, hinged hand hoes, shallow ploughs and harrow are being promoted. However, a more satisfactory long term solution may be obtained using chemical weed control. Of the most commonly available chemicals; butahclor, alachlor, and oxadiazon used extensively in rice, the first two proved the most useful in wheat. Oxadiazon gave the best broad spectrum weed control but caused mild severe phytotoxicity that resulted in yield reduction. Of the traditional wheat chemicals, the combination application of diclofop-methyl and chlorsulfuron is superior in weed control and consistently results in higher yield than with other chemical treatments.

BIBLIOGRAPHY

Dewey, W.G., and R.F. Nielson. 1968. Effect of early summer seeding of winter wheat on yield, soil, moisture and soil nitrate. Agron, J.

Klatt A.R. January 1923, 1987. Wheat Production Constraints in Tropical Environment. Chian Mai Thailand.

Martin, John H., and Warren H Leonard. Principles of Field Crop Prodution. New York. Mc Millan Publishing Co, Inc.

Peterson, R.F. 1965. Wheat World Crops Books, ed. L.N. Polunin Interscience