In this article we will discuss about:- 1. Origin and Distribution of Maize 2. Area and Production of Maize 3. Nutrient Management 4. Cropping Systems 5. Varieties and Seasons 6. Harvesting and Storage 7. Weed Management 8. Quality Considerations.
Maize (Zea mays), also known as corn, is the world’s third most important cereal crop after rice and wheat. With its average yield of 4.82 t ha-1 as in 2006, maize ranks first among cereals and is followed by rice (3.8 t ha-1) and wheat (2.7 t-1).
Maize is primarily grown for grain and secondly for fodder and raw material for industrial processes. World area under maize is about 145 M ha with a production around 695 M t and productivity 4.82 t ha-1 (2006).
Unlike many of the cereal grains such as wheat, rice and barley that evolved and were selected as food crops in the Old World, no wild forms of maize have been found. Scientists can readily find intermediates, if not the actual ancestral forms of Asian cereal grains growing wild today and can, therefore, develop models for evolution, domestication and cultivation of these grains. This is not so for maize. To date, no feral plant has been found having a reproductive structure remotely similar to the corn ear.
Origin and Distribution of Maize:
Cultivated maize may have originated from the pod corn indigenous to lowlands of Southern America. However, De Wet (1972) suggest that teosinte like grass could be the wild progenitor, although now extinct. Euchlaina mexicana (teosinte) is the closest wild relative of maize. Archaeological evidences suggest its cultivation 5000 years ago. Preserved pollen in New Mexico (USA) dates much earlier to 5600 years.
Greatest genetic diversity for maize is available in the South American continent and the centers of origin are per se Bolivia and Equador. Some prefer to believe that maize originated around southern Mexico and Central America. In fact, development of the centers of variability for maize types is believed to have coevolved with the development and spread of native America -Indian civilisation in the great continents.
Archaeological and botanical evidence suggest that maize was domesticated and existed by 5000 BC in central Mexico. Remains of cobs found in Peubla state of Mexico are the earliest dated remains. These cobs were from a very primitive race of maize, perhaps from an intermediate between teosinte and all extent maize races. These cobs are similar to teosinte cobs and the plants were more maize-like than teosinte-like in that cobs were non-shattering and had either four or eight rows of grains.
These cobs also are similar to most primitive stable biotypes or races of maize grown in western Mexico. From central and southern Mexico, maize culture spread in all directions
reaching northern Chile by 2700 BC and New Mexico by 1200 BC. Once introduced into the Old World by Columbus in 1493, maize culture spread to most of the eastern hemisphere within 100 years.
The antiquity of maize in India is not clearly established. It is, generally, believed that the Portuguese introduced it to India from Europe during the early part of sixteenth century. There is no evidence for its existence on the Indian plains in pre Columbian times.
Watt (1892) indicated that the vernacular names for maize did not throw any light on the history of maize in India. The most commonly occurring name makkai or makka, which would mean from ‘Mecca’, suggests introduction from outside India.
Area and Production of Maize:
Maize is one of the most important cereals of the world. In terms of world area, India stands next to USA, Brazil, China and Mexico, where as in production it ranks eleventh. Countries in the order of production are the USA, China, Brazil, Argentina, Mexico, France, South Africa, USSR, Rumania, Yugoslavia and India.
Maize has many assets for its wide distribution: its husk give protection from birds and rain, can be harvested over a long period since it can be left dried in the field until harvesting in convenient, can be stored long, provide numerous useful food products and frequently preferred to sorghum and other millets. As indicated already, it is cultivated in about 145 M ha in the world with a production around 695 M t.
Top five maize producing countries (M t) are:
1. USA: 331.17
2. China: 152.41
3. Brazil:52.11
4. Mexico: 23.51
5. Argentina: 21.7.
In India, maize is grown in an area of 8.17 Mha with a production of 19.73 M t and productivity 2414 kg ha-1. In terms of national hectarage, it ranks next to rice, wheat, sorghum and pearl millet. Though consumed all over the country, it is the staple food in hill and sub-mountain tracts of northern India.
As a fodder and grain crop, it is extensively grown in Karnataka, Rajasthan, AP, UP, MP and Bihar. As per 2008-09 statistics, Karnataka has the largest area under maize (1.07 M ha) followed by Rajasthan (1.05 M ha). Production is highest in AP (4.15 M t) followed by Karnataka (3.03 M t). Yield is highest in AP (4.87 kg ha-1) followed by TN (4.39 kg ha-1).
Considerable variation in grain yield is observed in the country depending upon the variety, fertiliser use and rainfall pattern. Under irrigated conditions, average yield of 4.0 t ha-1 in the Indo- Genetic plains is not uncommon. In Peninsular India and at higher elevations, a mean yield of 5.0 to 7.0 t ha-1 has frequently been obtained.
Under rainfed conditions with poor yielding varieties, grain yield ranges from 1.0 to 2.0 t ha-1. There is ample scope for increasing the productivity. The genetic potential of present hybrids is 7.5 t ha-1 and the realisable potential is 5.0 t ha-1 in comparison to national average of 1.7 t ha-1.
Nutrient Management in Maize:
Nutrient Uptake:
The average uptake of minerals by maize crop of 5 t ha-1 grain yield is 105 N, 50 P2O5, 75 K2O, 10 CaO, 10 Mg and 6 S kg ha-1. A detailed study of uptake and distribution of nutrients in different plant parts has been conducted by Karlen (1988). Total shoot nitrogen accumulation was approximately 386 kg ha-1 in 32 Mg ha-1 dry matter at physiological maturity.
Accumulation of nitrogen in lower leaves, upper leaves, stem and ear and ear and silk were about 122, 81, 56 and 255 kg ha-1 respectively. Total phosphorus accumulation was about 70 kg ha–1 and peak accumulation in lower leaves, upper leaves, stem and tassel and ear and shank were 13, 10, 9 and 59 kg ha-1, respectively. Phosphorus accumulation steadily increased until maturity.
During grain development, there was considerable translocation from vegetative parts to grain. With regard to potassium, 86 per cent was accumulated by silking and only 19 per cent of it was contained in ear and shank portion. Thus, most of potassium remained in stover.
In conclusion, the results of Karlen (1998) showed that the total accumulation at physiological maturity was approximately 31800, 386, 70, 59, 44, 40, 0.13, 0.14, 1.9, 0.9 and 0.8 kg ha-1 for dry matter, N, P, K, Ca, Mg, S, B, Cu, Fe, Mn and Zn, respectively. Such studies will provide general guidelines for high maize yields.
Nutrient Concentration:
Plant analysis has long been used in various ways to diagnose plant nutrient adequacy and estimate fertiliser needs. Table 4.5 provides values of adequate nutrient concentrations in maize plant at 30-45 days after emergence. These values can be used as a guide for identifying nutrient deficiencies or sufficiency in maize plant.
TABLE 4.5: Adequate nutrient concentrations in maize at 30-45 days after emergence in whole plant.
Nitrate Accumulation:
Under conditions of limited supply of soil moisture and low atmospheric humidity, plant may take up more NO3 than it requires due to either high concentration of nitrogen in the soil solution or high transpiration rate.
Before NO3 is used in the synthesis of amino acids and protein, it must be reduced to NH3. Inadequate supply or decreased activity of NO3 reductage system may slow down the reduction process. Consequently, metabolisation of NH4 is retarded and the danger of toxic levels being reached in the plant is increased.
Young maize plants must contain high levels of NO3 for optimum yield. As the ears develop, NO3 is reduced to amino form to supply for the protein synthesis. When the grain is mature, NO3 should be present in stalk below the ear but not above the ear.
Absence of NO3 in the stalk below the ear at maturity indicates scope for reduced yield due to shortage of nitrogen. Drought, high temperature, low P/K levels and excessive K fertilisation contribute to high NO3 content in maize.
Cropping Systems in Maize:
Rainfed Systems:
The largest area under kharif maize is in Uttar Pradesh followed by Bihar, Rajasthan, Madhya Pradesh and Punjab. Over 72 per cent of the area receives 200-300 mm per month rainfall in at least 2 or 3 months during the crop growing season. On all India basis, 12 cropping systems have been identified by the ICAR (2009). In Uttar Pradesh and Bihar rice in kharif and wheat in rabi are the alternate crops to maize.
In Rajasthan, maize is the exclusive crop in some areas and replaced by small millets, pulses, groundnut and wheat in other areas. In Madhya Pradesh, kharif sorghum is often replaces maize. In Punjab, groundnut, fodder corps and wheat are alternate crops.
Major cropping systems prevailing maize growing agroclimatic zones are indicated in Table 4.6. Short duration varieties of pulse crops (greengram, blackgram, cowpea etc.), oilseeds (groundnut, soybean, sesame etc.) can be intercropped with maize. One or two rows of the selected crops can be intercropped without any reduction in maize yield.
Irrigated Systems:
While Maize-wheat/safflower/jute/groundnut are major systems under ranifed conditions, maize- wheat/potato/sunflower/sugarcane/pulses are major systems under irrigation. Major systems are given in Table 4.6.
Varieties and Seasons of Maize:
There are four species of the genus Zea found in Mexico and northern central America. These include two perennials Z.perennis and Z.diploperennis and two annuals Z.luxurians and Z.mexicana, the common name teosintei. Zea mays is commonly called corn in USA but referred to as maize in other parts of the world.
Varietal Improvement:
Hybrid cultivars offer yield advantage over conventional cultivars. Commercial exploitation of hybrid cultivars was first made in maize in USA as early as 1878 but hybrid maize cultivation was made possible by Shull and Jones in the first two decades of the last century.
In India, maize hybrids were introduced from USA and Australia in early 1950s with yield advantage ranging from 30 to 50 per cent over traditional varieties. However, poor performance of inbred parents and unattractive grain type limited their introduction.
Hybrid breeding got a great fillip with the introduction of germplasm from USA, Colombia, Mexico, Caribbean countries and Latin America by Rockefeller Foundation and establishment of All India Coordinated Maize Improvement Project (AICMIP) in 1957. First set of four double cross hybrids was released in 1961 followed by many in 1960s. Due to seed production problems, hybrid maize could not become popular on the expected scale.
Focus was, therefore, shifted to open- pollinated composites and six composites were released in 1966. Realising the yield potential of hybrids and emergence of single crosses, research was initiated in hybrid maize in 1980s with emphasis on single-cross hybrid breeding.
First single-cross hybrid Paras was released for general cultivation in Punjab in 1995. This was followed by release of three early maturing single crosses Pusa Early Hybrid Makka 1, Pusa Early Hybrid 2 and Prakash. Maize cultivars recommended for kharif and rati are given in Tables 4.2 and 4.3.
Maize hybrids, proprietary hybrids and composites released in India during 2008 and 2009 as reported by Directorate of Maize Research (ICAR), New Delhi are given in Table 4.4.
Seasons:
Maize can be grown all over India but it is popular in northern and southwestern parts. There are three distinct seasons for maize cultivation.
Kharif:
It is the main season of maize cultivation although the country. Onset of monsoon (March- June) dictates the time of sowing rainfed maize.
Rabi:
In Peninsular India and Bihar, maize is grown during rabi (winter) under irrigation.
Summer:
In southwestern parts of the country, maize is grown with irrigation during summer (spring).
In Peninsular zone and southern Rajasthan, maize can be grown at any time during the year, provided irrigation water is available.
Harvesting and Storage of Maize:
Harvesting:
Maize crop grown for grain is harvested when the grains are nearly dry with moisture content of 20-24 per cent. Appearance of the plant may be misleading, particularly in the case of high yielding hybrids and composites whose grain are dry, while the stalk and leaves may be still green.
Ears are removed from the standing crop and dried before shelling. Maize grown for fodder should be harvested at milk to early dough stage. For silage, late dough stage harvest is ideal.
Dried ears (cobs) are shelled using both power and hand operated maize shellers available locally. Shellers are more efficient than hand shelling or beating with sticks, the common practice of small and marginal farmers.
Storage:
Shelled maize grain, after cleaning, is stored in sacks, earthen grain bins or those constructed with millet or maize stover. Maize grain for storage can have 15 per cent moisture if the storage period is less than 6 months. For longer storage, it should be dried to 13 per cent grain moisture content.
Seeds stored under controlled conditions of 30/75, 30/55, 30/33, 20/75, 20/55 and 20°C/33 per cent relative humidity and uncontrolled storage conditions indicated that the speed of deterioration up to 48 months was directly related to the temperature and moisture content in equilibrium with the relative humidity of the several storage environments.
The best controlled conditions for maintaining the longevity of the seeds were 20/33 and 20°C/55 per cent relative humidity. Studies on maize seed storages dried to 8.5 per cent moisture, in gunny sacks, sealed polyethylene bags and metal containers indicated that the germinability could be maintained up to 52 months in polyethylene bags and metal containers in a cold store but only 10-14 months in storage at room temperature.
Weed Management in Maize:
Maize crop is sensitive to weed competition during early growth period due to slow growth in the first 3-4 weeks. Maximum weed competition in maize occurs during the period of 2-6 weeks after sowing.
Cultural Methods:
Wider row spacing for maize is convenient for weeding between the rows with bullock or tractor drawn implements. Weeds within the row can be removed by manual weeding. One or two inter-cultivations with implements followed by manual weeding can effectively control the weeds. There should not be any inter-cultivation after flowering to avoid damage to maize crop.
Use of Herbicides:
Herbicides, which can prevent weed establishment during the first 6 weeks, are very useful in maize.
The following herbicides are effective for weed control in maize crop:
PRE herbicides:
Combination of Alachlor (1.5-2.0) + Atrazine (1.0) ft more effective on a broad spectrum of weeds including grasses and broadleaf weeds. Atrazine and Simazine are more effective on broadleaf weeds than grasses, while Alachlor has greater activity on annual grasses.
Other PRE herbicides, which can give good control of mixed weed spectrum include:
POST herbicides:
Atrazine shows good POST activity when tank mixed with Phytobland oil and applied at 2 to 4 leaf stage.
PPI herbicides:
Trifluralin (0.8-1.2)
Butylate (4.0-6.0)
EPTC (2.0-4.0)
These herbicides provide season long control of several weeds. They can control nutgrass and many annual weeds.
Quality Considerations of Maize:
Maize grain is either transformed into flour to prepare different types of breads, biscuits, cookies etc. or transformed into corn flakes, soups and other preparations. Grains can also be roasted or popped for direct consumption. Maize grain is also used as cattle feed. Fodder and silage of maize are important cattle feeds. Maize has a multitude of industrial uses.
Quality:
Maize grain is mainly composed of germ and endosperm. The embryo contains most of good protein and oil whereas the endosperm contains most of the carbohydrate. On an average, maize grain is composed of 80 per cent carbohydrates, 10 per cent protein, 4.5 per cent oil, 3.5 per cent fibre and 2 per cent minerals.
Maize grain is deficient in essential amino acids, lysine and tryptophane. Quality protein maize (QPM) opens new vistas and exciting prospects to improve the nutritional quality of maize. Protein content of the two QPM cultivars Shaktiman 1 and 2 is 11 per cent as against 9-10 per cent in normal maize. Tryptophane and lysine contents in QPM are 0.11 and 0.475 per cent as against 0.05 and 0.225 per cent, respectively in normal maize. Due to high biological value, the QPM can fit well in infent foods and other preparations aimed at energy rations.
Speciality Maize:
Due to the immense genetic variability expressed in maize, genes that confer distinctive characteristics have been identified for special markets and uses. Among these genes, some influence sugar content in grain while others effect carbohydrate and protein composition.
Popcorn:
Flint corn with maximum popping expansion is referred to as popcorn.
Sweet Corn:
The conversion of sugar to starch is slowed in sweet corn compared with normal corn. It is consumed only fresh or canned, since dry kernels have wrinkled appearance.
High Amylose Corn:
The kernels have waxy appearance, relative to the skinny kernels of flint and dent. The endosperm is 100 per cent anylopectin or branched chain starch compared to about 70 per cent for normal corn. This allows certain processors to bypass the separation step in the production of purified starch. High amylose maize, also known as waxy corn, has application in food, paper, textile and adhesive industries.
Baby Corn:
It is recognised as chemical free vegetable product. Un-fertilised young ears are harvested and consumed in salads and for numerous stir-fried dishes. It is popular in China, Taiwan, Japan and Thailand.
QPM:
Quality protein maize has improved protein quality in terms of lysine, tryptophane and amino acids, which are deficient in normal maize.