In this article we will discuss about the climatic condition suitable for cultivating sugarcane.
Sugarcane is a tropical plant and thrives best in hot sunny areas where temperature, light and moisture are the principal climatic factors that control cane yield. A warm summer growing season with adequate rainfall is an ideal climate for sugarcane production.
Globally, sugarcane is grown from 37°N in southern Spain to 31°S in South Africa. Optimal performance is observed around 20° latitude. In India, it is grown from 8° to nearly 33°N and mostly from sea level to 1,500 m.
Sugarcane cannot tolerate freezing temperatures and growth ceases at mean minimum temperature below 12°C. Maximum photosynthetic rates occur at air temperature of about 34°C. The ideal climate for a one year crop would include at least 4 to 5 months with mean daytime temperatures of 30° to 35°C to stimulate growth and 1.5 to 2 months of cooler temperatures prior to harvest to enhance sucrose accumulation.
The ideal temperatures for growth and development of sugarcane are:
1. Carbon assimilation 30°C
2. Sugar synthesis 30°C
3. Sugar transport 30-35°C
4. Tillering 33.3-34.4°C
5. Root growth 36°C (soil)
6. Shoot growth 36°C (soil)
Relationship between Yield and Climate:
The association of climatic parameters with average yield of states in India has been worked out with conclusions indicated in Table 18.1.
1. Mean annual temperature with observed cane yield is positively correlated (r = 0.6672)
2. Standard deviation of mean annual temperature with cane yield is negative (r = -0.79).
3. There is highly negative correlation between annual temperature and coefficient of variation of mean monthly temperature. Thus, states showing lesser annual mean temperature also have high variability. Relative temperature disparity factor (RTD) has been worked out.
Climate parameters such as mean temperature, its variation in annual march of season, annual rainfall, sunshine hrs, relative humidity and RTD have been related to cane yield and sugar recovery (Table 18.1).
It has been found that during the growth phase, the mean temperature should be high with lesser variation between mean monthly temperatures. Tamil Nadu, Karnataka, Maharashtra and Andhra Pradesh show high mean temperature with lesser variability in monthly means and hence the observed yields are high.
Though, Kerala has higher mean temperature and lesser variability in monthly means, its yield is relatively low because its RTD is the lowest. When all the climatic parameters are nearing optimum, the observed cane yields are high. In Karnataka, the daytime temperature is well above 30°C, relative humidity highest in the growth phase (April – October) and rainfall (1,354 mm) well distributed leading to high cane yield.
In India, sunshine hrs are not limiting cane yield. Rainfall, relative humidity and RTD factors do not have strong individual effects but have modifying effect conjointly. Thus, in Rajasthan, temperature is more favourable than in Assam but it shows high variability, high aridity with lowest humidity and low annual rainfall compared with other states and hence the yield is low.
Maharashtra, Karnataka and Gujarat show high sugar recovery per cent due to quite favourable mean minimum temperature and RTD values during cane ripening (November-February). In Punjab and Rajasthan, the mean minimum temperature during ripening phase is relatively low (8°-10°C) and hence the sugar recovery is lower in spite of favourable RTD values.
In general, the states with RTD values around 40-50, mean minimum temperature around 14°-18°C, low relative humidity (50-60%) with low daily mean temperature (22°-26°C) during cane ripening period register high sugar recovery.
Agroclimatic Zones:
In India sugarcane is cultivated both in tropical and subtropical regions.
Tropical region:
Andhra Pradesh, Gujarat, Kerala, Maharashtra, Karnataka, Orissa and Tamil Nadu.
Subtropical region:
Assam, Haryana, Bihar, Madhya Pradesh, Nagaland, Punjab, Rajasthan, Uttar Pradesh and West Bengal.
Although, cane area in tropics is around 40 per cent of subtropics, can production is about 80 per cent reflecting higher productivity rates in tropics. The sugar recovery is also higher in tropics (8.5 to 11.5%) compared with subtropics (8.0 to 9.5%).
The Sugarcane Breeding Institute, Coimbatore recognised seven sugarcane agro-climatic zones, four in subtropical belt and three in topical belt.
However, they are condensed to five zones as given below:
1. Northwest Zone.
2. Northeast Zone.
3. Northcentral Zone.
4. Eastcoastal Zone.
5. Peninsular Zone.
The Government of India has demarcated sugar factories into regions of low, medium and high recovery areas as shown below:
Low (blow 9%):
Punjab, Haryana, north Bihar, south Bihar, Kerala, Orissa, Assam and West Bengal.
Medium (9-10%):
Western Uttar Pradesh, central Uttar Pradesh, Rajasthan, Madhya Pradesh, Andhra Pradesh, Tamil Nadu (with 8.6 per cent recovery but due to long duration of crushing exceeding 185 days included in medium class).
High (more than 10%):
Maharashtra and Karnataka.
Soils:
Sugarcane crop can be grown on various types of soils from sand to heavy clay provided the climate, water, drainage, fertility and depth are favourable. Moderately heavy and medium deep (1-2 m) loams are better suited than heavy, light or shallow soils. In general, sugarcane crop requires adequately aerated soil profile to a depth of at least 40 to 60 cm without compaction, hard pan and lime band or salt zone in subsoil.
Alluvial, black, red and lateritic soils, coastal alluvium and saline and alkali soils are the major sugarcane growing soils in India. Alluvial zone covers states of Uttar Pradesh, Bihar, Haryana, Punjab and West Bengal. Shallow to medium black soils predominate in Maharashtra and Karnataka.
In Andhra Pradesh, sugarcane is largely grown on black soils as in Godavari, Nellore and parts of Telangana. In Rayalaseema and Agency tract, it is grown on light red soils. Alluvial soils predominate in Godavari and Krishna districts.
Sugarcane can tolerate soil pH ranging from 4 to 9, though nutritional problems may occur at the extremes. Some varieties may tolerate moderate salinity and seasonal flooding. However, adequate drainage is necessary for high yield. Sugarcane is considered moderately susceptible to soil salinity.
The salinity threshold (initial yield decline) has been reported to be 1.7 dS m-1 and the yield decrease per unit increase in salinity beyond threshold is 5.9 per cent. Serious yield reduction occurs at a conductivity of 4 to 8 dS m-1 and very little growth or death occurs above 10 dS m-1.
Tillage:
Sugarcane requires a very thorough and clean preparation of land. In Peninsular India, where sugarcane soils are mostly clays and clay loams, one or two deep ploughings and one cross- ploughing with a mould board plough are necessary. These operations should be followed by clod- crushing with a discharrow or a junior cultivator or a beam clod-crusher or even with wooden mallets and stout sticks.
In the alluvial loams of northern India, cultivators usually prepare their fields after winter rains, but when these rains fail, the fields are given a preparatory irrigation and ploughed with desi plough to a fine tilth. In Bihar, the fields are left fallow during the preceding monsoon and are cultivated at intervals up to the time of planting cane. All this is done in order to conserve moisture and keep down weeds.
Cattle manure, compost and other slow acting bulky organic materials are usually applied to the soil and incorporated into it well in advance of planting. This practice helps to decompose the manure and makes the nutrients available.
Where cane is green-manured, the leguminous crop should be ploughed under about a month before planting the cane. In northern India, however, where a clod season intervenes, the green-manure crop is ploughed under in September and cane is planted several months later.
Sugarcane is planted either in furrows or trenches. Depending on the method of planting and the fertility of the soil, furrows or trenches are made half to one-and-a-half metres apart. Comparatively narrow spacing are adopted in north India, where yields are usually low, whereas wider spacings are common in Peninsular India where the aim is to obtain high yields.
Furrows are made with a padded desi plough in northern India and with a heavy double mould-board ridger in Peninsular India. Furrows made with the desi plough are quite shallow, being about 10 cm deep, whereas those made with a ridger are about 20 cm deep.
Where trench planting is adopted, trenches are dug by hand-labour, using pick-axes and spades and may be up to 25 cm deep. On large farms, all preparatory cultivation, including ploughing, clod crushing, harrowing and ridge making are mechanised.
The adequacy of moisture is very necessary for the setts. In Peninsular India, arrangements for irrigation are made well before planting. In northern India and in Bihar, care is taken to conserve as much moisture in the soil as possible, so that the planted cane is able to germinate satisfactorily.
All the same, as the planting is necessarily done during the comparatively dry season, considerable loss of moisture from the soil and sets takes place and usually only 30 to 40 per cent of the buds germinate.