In this article we will discuss about the climatic requirements for maize cultivation.
Maize can be grown over a wide environmental range. It is essentially a crop of warm countries with adequate moisture. Bulk of the crop is grown in warmer parts of temperate regions and in humid subtropics. It is mainly grown from 50°N to 40°S and from sea level to 4000 m in Andes and Mexico. The lowest seasonal rainfall in maize area is 200 mm.
However, available evidence indicates that maize as purely rainfed crop may be risky in regions with mean annual rainfall of 400 mm and that even in areas receiving 600 mm rain, irrigation appears to be necessary for realising high yield. It cannot withstand frost at any stage of its growth. In India, its cultivation extends from the arid plains of Rajasthan and Gujarat to wet hills of Assam and West Bengal receiving over 4000 mm rainfall.
It can be successfully grown where the night temperature does not go below 15.6°C. The greatest intensity of maize cultivation is in the region bounded by the July isotherms of 20° and 20°C. In general, maize in temperate regions is what sorghum is in tropical areas.
The latitude of maize growing in India ranges from 12° to 30°N. The range in altitude is from 49 m in Bihar to 1,250 m in Himachal Pradesh. Maximum temperature during June when maize is sown often exceed 40°C in some areas, while minimum temperature during winter is favourable for maize in several states like Bihar, Uttar Pradesh, south Rajasthan and Karnataka with moderate to low rainfall.
Annual rainfall requirements vary from 513 mm at Arabhavi (Karnataka) to about 2,200 mm at Almora (Uttar Pradesh) and Kalimpong (West Bengal). Most of the rainfall is received between April and October at many locations.
1. Germination:
Soil temperature of 26° to 30°C is optimum for both germination and seedling growth. Minimum temperature for germination is 10°C. Jain (1973) considers that the ideal temperature for maize germination is 21 °C. Emergence is normally reduced below 13°C and fails below 10°C. For uniformity of initial stand, a minimum temperature of 17° to 20°C is necessary.
In higher altitudes as in north Europe, North America etc. where maize is sown in spring, low soil temperatures prevent early seeding. Earlier germination may subject the crop to freezing temperatures besides hastening flowering leading to reduced crop duration. Too late a sowing to ensure optimum temperature for germination encourage pest and disease problem. Hence, there is a need for day neutral spring maize in higher altitudes.
2. Vegetative Phase:
The range of temperature for maize growth is from 9° to 46°C with optimum around 34°C. Thus, all these values maximum, minimum and optimum are 4° to 6°C higher than those of wheat or barley. When mean daily temperatures are below 20°C, crop duration will be extended by 10-20 days for each 0.5°C decrease depending on variety. At 15°C, the maize for grain may take more than 200 days to mature.
Temperature requirements, expressed as sum of mean daily temperature for medium duration cultivars are 2,500 to 3,000 degree days, while early cultivars receive about 1,800 and late cultivars more than 3,700 degree days.
Little root growth occurs at 10°C, while even at 17°C the root growth may be less than 1.5 mm day-1. More than 40°C severely inhibits root growth. The optimum is around 34°C. Jain (1973) considers that the ideal temperature for crop growth is around 32°C.
Maize is more resistant to drought. The crop can recover from early season drought. Maize is sensitive to freezing temperatures except in very early stage and can recover from the effects of frost if it occurs when the plant is less than 15 cm height.
Very young seedlings are less susceptible to high temperatures. From these findings, it is evident that maize can recover from early adverse climatic conditions during early stage. Hence, early sowing of maize with onset of rains, even at the risk of early drought due to late onset of regular rains is recommended. Similarly, early sowing to avoid pest and disease may be resorted to even at the risk of freezing temperatures during early crop period.
3. Reproductive Phase:
In this stage, temperatures above 32°C as well as frost can reduce yield. Hailstorm is most harmful between jointing and silking stages. Soil moisture stress prior to silking, during silking and after silking reduces grain yield, respectively by 25, 21 and 50 per cent.
Optimum temperature at tasseling is 21° to 30°C. High temperature promotes respiration. Average respiration loss is about 25 per cent of photosynthetic rate in temperate zone and 35 per cent in tropics. However, an important effect of temperature is that high temperature, particularly at night, shortens grain filling period there by reducing the yield.
High temperature increases the rate of grain filling but greatly reduces the duration of grain filling period, whereas low temperatures cause an inverse response. The grain yield of maize, like other small grains, is higher at lower temperatures because of an increase in the length of grain filling period and greater partitioning of photosynthesis dry matter to grain. A detailed description of climatic requirements of corn is given by Shaw (1977).
It has been concluded that the ideal climate for maize is winter having mean temperature regime of 18° to 23°C with 100 mm rainfall per month in the crop growing period except the last month.
4. Soils:
Maize can be grown on a wide variety of soils but performs best on well drained deep loams and silt loams containing adequate organic matter and available nutrients. It is necessary that the pH of soil does not deviate from the range 7.5 to 8.5. Maize plants, particularly at the seedling stage, are susceptible to salinity and 90 per cent relative yield was obtained at an electrical conductivity of 1.8 dS m-1.
Soil salinity can have a marked influence on uptake of nutrients but decreased dry matter production probably most often due to decreased soil water and increased toxicity of sodium chloride and sulphate in the soil solution.
Shoot growth of the seedlings was reduced by about 5 per cent for each unit increase in salinity from 0.7 dS m-1 to 15 dS m-1. However, salinity tolerance was high up to 9 dS m-1 during post-vegetative growth stage. Yield decrease under increasing salinity could be 10 per cent at 2.5 mm hos cm-1, 25 per cent at 3.8, 50 per cent at 5.9 and 100 per cent at 10 mmhos cm-1.
Maize is also sensitive to waterlogging. Accordingly, provision of adequate drainage is essential for economic production. Light soils facilitate drainage but have relatively poor water holding capacity. On the contrary, heavy soils with good water retentivity have relatively poor drainage. Hence, soils ideally suited for maize crop should have adequate water holding capacity and also good drainage.
5. Maize Zones:
Maize improvement project in India demarcated maize cultivated areas in the country into four broad zones:
i. Himalayan Zone:
It includes temperate regions above an elevation of 600 m that receive moderate rainfall. Crop duration is usually longer.
ii. Northwest Plains Zone:
This zone is characterised by wet and arid climate below 600 m above MSL. Soil moisture stress at flowering and grain filling is common. Soils are sandy and rarely alluvial. Medium to early maturing cultivars are preferred. Ground frosts may be a problem during winter season.
iii. Northeast Plains Zone:
Hot and humid climate with frequent waterlogging. Maize can be cultivated in three seasons: monsoon, winter and spring. Soils are Oxisols with low nutrient status.
iv. Peninsular Zone:
This zone is characterised by tropical to subtropical climate. Coastal areas favour maize cultivation although the year, if irrigation water is available. Soils are medium deep to very deep. Deep soils need drainage provision during heavy monsoon rains.