By Khawar Jabran, Dr Zahid Ata & Dr Muhammad Farooq
MAIZE ranks third most grown crop in the world with an area of more than 118 million hectares with an annual production of about 600 million metric tones. In Pakistan, maize is the fourth largest grown crop after wheat, cotton and rice. The area under maize here is over one million hectare and production 3.5 million metric tonnes.
Punjab contributes 39 per cent of the total area under maize and 30 per cent of total production; NWFP contributes 56 per cent of the total area and 63 per cent of the production while five per cent of the total area and three per cent of the total production is contributed by Sindh and Balochistan.
Maize has a variety of uses. Its grain is a rich source of starch, vitamins, proteins and minerals. One hundred gram of fresh grain contains 361 calories of energy, 9.4 g protein; 4.3g fat, 74.4g carbohydrate, 1.8g fibre; 1.3g ash, 10.6 per cent water, 140mg vitamins, 9mg calcium, 290mg, phosphorus and 2.5mg iron.
In the green state, maize can be parched, baked, roasted, boiled or steamed on the cob. Maize flour has a very mild flavour and is used for making breads and as a thickening agent in foods such as custards and jellies. Popcorn is kernels of certain maize that burst when heated, forming fluffy pieces that are eaten as a snack.
The starch extracted from maize grain is used in making confectionery and noodles. Corn syrup from maize contains high fructose and act as sweetener and retains moisture when added to certain foods. Edible oil is extracted from maize seeds, which is an all-purpose culinary oil.
Levulinic acid, a chemical derived from maize, is used as ingredient in antifreeze and is capable of replacing the toxic petroleum-based ingredients in use. Plastics and fabrics are made from corn stocks.
Ethanol obtained from maize can be used as a biomass fuel. Stigmas from female corn flowers, known as corn silk, can be used as herbal supplements. Maize straw is a cheap source of energy and can be used in home-heating furnaces.
Maize can be used as forage, feed for livestock and making silage after fermentation of corn stocks. Maize is used extensively as the main source of calories in animal feeding and feed formulation. Maize gives the highest conversion of dry substance to meat, milk and eggs compared to other cereal grains. Maize is a valuable feed grain, because it is among the highest in net energy content and lowest in protein and fibre content. Animals like and eat it readily.
The maize hybrids possess capability of producing more than 12 tones grains per hectare which is very high as compared with 3.48 tones per hectare, the average yield of maize in Pakistan. Important hybrids available in Pakistan include High corn-8288, NK-8001, X-2276, Monsanto-6525, Monsanto-919, Pioneer-3335, YHD-555 and FSH-523. The gap between the realised and potential yields can be bridged up by adopting suitable agronomic practices and minimising the biotic and a biotic stresses on the crop.
Soil and Climate: Maize is adapted to wide variety of soil and climate and can be grown from coastal areas to high altitude. Maize required a temperature of more than 10 0C to flower. Soils with a pH range of 6.5-7.5 are most favourable. Well drained, heavy soils with high organic matter content and good water holding capacity give high produce.
Seed bed preparation, Sowing dates and Sowing Method: Favourable conditions for germination and seedling establishment are the important objectives of seed bed preparation. Fine and compact bed is needed for maize. The land with optimum moisture after rainfall or irrigation is loosened 20-25 cm deep through ploughing or disking 2-3 times, immediately followed by planking.
In Pakistan, maize crop is sown mainly in two seasons; spring and the autumn season. Spring maize can be planted in the first week of February up to first week of March while the sowing time for autumn maize starts from the last week of July and ends in mid of August. Seed rate for maize is 20-25 kg per hectare. Seed is dressed with some systemic insecticide, for example imidacloprid at the rate of 1g per kg of seed.
Maize can be sown on both flat soils as well as on the ridges. Ridge sowing is better for water saving. Ridges are made 75 cm apart with a tractor drawn ridger. Choka method or manual sowing is practiced for ridge sowing. In case of flat sowing, maize is sown with automatic tractor drawn drill or manual/hand drill with 75 cm distance between the rows. Thinning is done after 10-15 days of emergence, consisting pulling out or cutting the weak plants and maintaining a plant to plant distance of 20-25 cm. A plant population of 70,000 to 75,000 per hectare is inevitable to harvest optimal yields.
Fertilizer: Fertiliser rate for maize is 150-100-100 kg nitrogen, phosphorous and potassium per hectare respectively. All phosphorus and potassium while half nitrogen are side dressed with sown seed rows while the remaining half N is added to soil in 2 splits, first when the crop is at knee height and second at tasseling.
Plant Protection Measures: Immediately after emergence, maize crop faces a serious threat of shoot fly and stem borer attack. Stem borer bores into the stem and makes a hole in the stem. Furadan powder should be dropped into the shoots or broadcast at the rate of 20 kg ha-1 followed by irrigation. This practice should be repeated twice at 1-2 week interval.
Weeds reduce maize yield by 29-43 per cent or even more. Competition of weeds with maize plants is maximum 2-5 weeks after crop emergence. The most common weeds of maize in Pakistan include purple nutsedge (deela), horsepurslane (itsit), slender amaranth (jangli chulai), digera (tandla), jungle rice (jangli swank), burclover (maina) and swine cress (jangli haloon).
Common herbicides effective to control these weeds include Primextra Gold at 800 mL per acre, Pendimethalin at 1300 mL per acre and Dewal Dold at 800 mL per acre used as pre-emergence to weeds. While atrazine at 350 mL can be used as early post emergence 15 days after weeds emergence. A hand hoeing about 25 days after sowing provides satisfactory weed control at small scale.
Irrigation: Maize is drought sensitive crop and requires frequent irrigations for successful vegetative and reproductive growth. An irrigation within 10-15 days interval results in good growth. Drought will restrict many physiological processes leading to reduced yields.
Moisture stress at critical stages i.e. flowering, fertilisation or milking may cause a yield reduction up to 40 per cent due to reduction in number of grains per cob. Total number of irrigations for maize may vary from 6-9 depending on climate, soil type and method of sowing.
Harvest and Post Harvest: Maize crop is harvested when the moisture content of the grains are 20-25 per cent. The cob sheath dries completely at this stage, some drying may occur on the stalk. Cobs are removed from standing crop and dried under sunlight until the moisture content of the grains is below 15 per cent.
Hand operated or powered maize shellers are better than manual or hand shelling for safe exclusion of dried maize grains from cobs. Shelled maize grains after cleaning are stored in jute sacks in a cool, dry and airy place, either on a cement floor or on wooden planks; it should not be stored on earthen floors. The temperature of store room is kept 20-25 0C while relative humidity is maintained at 30-50 per cent.
Maize has prospective to play major role in nutrition of Pakistani people. It can act as the alternate food source when the conventional cereal grains i.e. wheat and rice are deficient.