Introduction to Sorghum:
Sorghum is mainly concentrated in Peninsular and Central India. The crop is being grown in practically all the States, but the main areas of the production are those with a low rainfall, that is Maharashtra, Andhra Pradesh, Karnataka, Madhya Pradesh, Gujarat, Tamil Nadu, Rajasthan and Uttar Pradesh. The total area under sorghum in this country is 7.76 million ha with total production of about 7.93 million tonnes.
In India, the average yield of grain sorghum is lowest (1.02 t/ha) amongst the major sorghum producing countries. World’s average yield of sorghum is 1.37 t/ha.
Climate Required for Sorghum :
Sorghum is a crop of warm climate but can be grown under a wide range of climatic conditions. It is grown in the semi-arid tropics from sea-level to an altitude of 3,000 m in variable rainfall areas. Sorghum plants can tolerate high temperatures and dry conditions better than any other cereal crop because of its extensive root system (absorb moisture from deeper soil layer), waxy leaf surface, small leaf area, and ability to curl leaves (that reduces transpirational loss of water). In addition, during a growing season, sorghum can survive periods of moisture stress by becoming dormant and then resuming growth when conditions become favourable. That’s why it is referred to as “the camel” of world’s crops.
Soil Required for Sorghum :
Sorghum is generally grown on almost all types of soils but, sorghum soils in India may be grouped into Alfisols (red) and Vertisols (black). It does not thrive in sandy soils. Soils having good water retentive capacity and are rich in organic matter contents are best suited. Crop is grown in pH range of 6.0 to 8.5.Black cotton soils of central India with proper drainage are considered as best soils for its cultivation. During kharif season, water logging is a problem in vertisols with high clay content. In general, vertisols with stored available soil moisture of about 90-120 mm is found to support a good rainfed rabi crop.
Sowing Time of Sorghum:
Sorghum is sown thrice in a year. It is sown in kharif and summer in north. In south and west, it can be grown in kharif, rabi as well as in summer seasons. In kharif under rainfed situations, the onset of monsoons is the single most factors deciding sowing time. The sowing time of sorghum is important aspect in increasing the crop yield. The sowing time is related with the soil moisture and soil temperature, as well as incidence of shoot fly.
Seed Rate and Spacing:
Three components to be considered for optimum plant population are; seed rate, planting geometry and total plants/unit area. Investigations in the All India Coordinated Sorghum Improvement Project (AICSIP) suggests that a density of 1.80 lakh plants/ha (18 plants/m2) is optimum in kharif season.
This can be achieved by planting at 45 cm x 12.5 cm or 60 x 9.5 cm. Generally 7-8 kg/ha seed is used. This provides 2 lakh plants/ha providing an allowance of 10 % loss, either due to poor germination or due to pest damage. In rainfed rabi crop, the optimum population is little lower i.e., 1, 35,000/ha i.e., about 14 plants/m2. whereas under limited moisture conditions, the rows should be widely spaced. Generally, the seed is sown to a depth of 3-4 cm. After germination, plants in the rows are thinned at the desired spacing.
The seeds are also treated with some bio-fertilizers for easy and enhanced availability of important nutrients like nitrogen and Phosphorous.
Seeds are treated with Carbofuran to prevent shoot fly infestation.
Method of Sowing:
Thinning is a very important cultural operation in sorghum for maintaining optimum plant population. In rows, plants should be thinned out to maintain 15-20 cm plant spacing at 2 stages. First thinning should be done 10-15 days after emergence and the second at 20-25 days after sowing. All diseased and insect infested or weak plants of sorghum should be removed while thinning.
Manures and Fertilizer Required for Sorghum :It responds well to organic and mineral fertilizers.A grain sorghum crop yielding 50-60 q/ha, removes about 130-180, 50-60 and 100-130 kg/ha of N, P2O5 and K2O, respectively.
However, in the absence of soil test results, the recommended fertilizer application need to be followed. For rain fed crop 6-7.5 tones of Farm Yard Manure (FYM) need to be applied before last ploughing and then properly incorporated.
Full quantity of phosphorus and potash along with 50% N should be drilled in the furrows at 10-12 cm deep in the soil or 5-7 cm below the seed at the time of sowing. Remaining N should be applied in two equal splits. Half of the remaining N (25% of total N) should be top dressed 25-30 days after sowing at the time of thinning in bands 7-8 cm away from the plant rows in shallow furrows and covered with the side soils.
Water Management for Sorghum :Maintaining optimum soil moisture at 20-25 DAS helps in development of strong secondary roots.In general, the water requirement of sorghum varies from 300- 500 mm (kharif and rabi) to 600-700 mm (summer). To produce one kilogram of dry matter, sorghum consumes 291 kilogram of water.
Weed Management for Sorghum :
Another pre-emergence herbicide recommended for jowar is prometryne @ 1 kg/ha. The integration of above herbicides with one hand weeding or hoeing 35-40 DAS may effectively control most of the weeds.
Striga or witch weed (Striga litura L.), a root parasitic weed is a menace in many sorghum growing regions of Maharashtra, Karnataka and Andhra Pradesh, that causes 15- 100% loss in yield depending on severity of its infestation.
Harvesting, Post Harvest, Threshing and Yielding of Sorghum:
Mature grain sorghum in the field contains about 30 % moisture. At moisture levels higher than 25 %, the seeds are too soft to withstand the threshing action. The right time for harvest is when grains become hard and contains 15-20% moisture.
Generally 2 methods of harvesting i.e. stalk cut and cutting of earheads by sickles are adopted. However, in foreign countries, sorghum harvesters are used In case of stalk cut method, the plants are cut from near the ground level. The stalks are tied into bundles of convenient sizes and stacked on the threshing floor. After 2- 3 days, the earheads are removed from the plants.
Threshing of earheads is done either by beating them with sticks or by trampling under bullocks feet. The later method is quicker and adopted by majority of farmers. Threshing is also done with the help of threshers. The threshed grain should be cleaned by winnowing and dried in sun for 6-7 days to reduce the moisture content to 12-13 % for safe storage.
The grain yield of improved varieties under assured water supply ranges between 2.5- 3.5 tonnes/ha, and that of hay or karvi between 15.0-17.0 tonnes/ha. With improved cultural practices, it is possible to harvest about 5.0 tonnes of grain and about 10.0-12.5 tonnes of dry stover/ha under irrigated conditions.
Young plants of sorghum (30-40 days) contain cynogenic glucoside ediately should be avoided.