Everything you need to know about sorghum cultivation in India. Learn about:- 1. Introduction to Sorghum 2. Climate Required for Sorghum Cultivation 3. Soil 4. Field Preparation 5. Sowing Time 6. Manures and Fertilizer 7. Water Management 8. Weed Management 9. Cropping Systems 10. Special Practices 11. Drought Mitigation 12. Harvesting, Threshing and Yielding 13. Varieties.
Sorghum Cultivation in India
Contents:
- Introduction to Sorghum
- Climate Required for Sorghum Cultivation
- Soil Required for Sorghum Cultivation
- Field Preparation for Sorghum Cultivation
- Sowing Time of Sorghum
- Manures and Fertilizer Required for Sorghum Cultivation
- Water Management for Sorghum Cultivation
- Weed Management for Sorghum Cultivation
- Cropping Systems of Sorghum
- Special Practices for Sorghum
- Drought Mitigation in Sorghum through Contingency Planning
- Harvesting, Threshing and Yielding of Sorghum
- Varieties of Sorghum
1. Introduction to Sorghum:
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. Average yields of sorghum are lower than important grain crops (maize, rice, barley and wheat). The lower average yield are primarily a result of the hot, dry conditions where sorghum is mostly grown, rather than sorghum plant capability.
One of the reasons of low production of sorghum is the low per hectare grain yield due to traditional system of cultivation, slow spread of high yielding varieties and hybrids in the country as well as the low and erratic distribution of monsoon rains, as maximum area under sorghum is concentrated in dry/rainfed zones of the country.
It is observed that food habits of sorghum eating people are changing towards rice and wheat products. Perhaps this, and reduced market price for sorghum have resulted in the decline of area under sorghum cultivation. Naturally, the poor farmers of rainfed areas who cannot grow crops other than sorghum are economically affected as they are not getting reasonable price of sorghum in the market.
The best ways of increasing the sorghum production and productivity in the country are as follows:
1. Replacement of traditional tall, low yielding varieties of sorghum with fertilizer- responsive high yielding varieties and hybrids.
2. Cultivation of hybrids and varieties with region specific suitable agronomic practices.
3. Protection of the crop from the attack of insect-pests and diseases.
4. Proper moisture management and timely intercultural and weed control.
2. Climate Required for Sorghum Cultivation:
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. The ability of sorghum to grow in drier environments is due to a number of physiological and morphological characteristics-
1. Produces many roots compared to other cereals,
2. Has reduced leaf area thus reducing water loss through transpiration,
3. Can remain dormant during drought and resume growth when conditions are favorable,
4. Above ground parts of plant grow only after the root system is well established,
5. The leaves have a waxy coating and have the ability to roll in during drought thus effectively reducing transpiration, and
6. Competes favorably with most weeds.
The minimum temperature for germination of sorghum seed is 7-10°C. It needs 25- 30°C temperature for its optimum growth. Though it can withstand temperatures up to 45°C, but the lower temperatures (<7°C) limit its cultivation owing to impaired flowering and pollination.
Hence, its rabi cultivation is restricted in north India. Temperatures below 13°C at blooming stage are detrimental to seed setting. It is a short day (the optimum day lasts 10 hours) and belongs to C4 group of plants. Flowering is hastened by short days and delayed by long days. The time of heading in sorghum is influenced by temperature as well as photo- period. It can also tolerate waterlogging conditions better than any other cereal except rice.
It can be grown successfully in areas having average annual rainfall between 40 and 100 cm. Sorghum cultivation during kharif is declining in the country as prolonged rains at flowering stage aggravates the incidence of grain mould disease as the infected grains become unfit for human consumption. High rainfall at heading stage reduced pollination and give poor yield. It has been found that rate of kernel development is higher at higher temperature than any other cereals.
3. Soil Required for Sorghum Cultivation:
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. However, in soil with low water holding capacity, winter showers or irrigation is necessary.
4. Field Preparation for Sorghum Cultivation:
Sorghum crop requires a well prepared seed-bed for good stand establishment. The cloddy seed-bed leads to uneven stand. Fine and firm field ensures better germination, improves soil aeration, helps in better root development, improves soil water intake, storage and absorption by plant roots and also reduces evaporation losses.
The field is prepared by deep summer ploughing every year in shallow to medium deep soils, and once in 3 years in deep to very deep soils. This should be done soon after harvest of rabi crop in double cropped regions, immediately after cessation of S-W monsoon. This leaves the field cloddy, exposing weed and other pests to high temperatures. The cloddy field also helps in moisture conservation.
With the onset of monsoon, the field is prepared by one deep ploughing followed by 2-3 harrowing or ploughing with country plough. Planking should be performed after each ploughing to break the clods and to level the field. In heavy soils prone to water logging, leveling is necessary to facilitate easy drainage.
5. 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.
Experiments conducted in major kharif sorghum tracts suggested that last week of June to first week of July (onset of monsoon) is the optimum time of sowing. Dry sowing just before the onset of monsoon is also reported to be the best.
Dry sowing is done in anticipation of rain. It aids in establishment of crop as an early opportunity and gives advantage of efficient use of rainfall during crop season. It can be practiced in deep black soils. Seeding should be relatively deeper than normal to avoid seed damage due to inadequate rainfall than that required for seed germination and emergence.
In case of irrigated conditions, the crop establishment before onset of monsoon is ideal. Thus, 1-2 weeks advance sowings before monsoon are adopted. Early sowing helps in minimising the incidence of shoot fly and less damage to the crop. Extra early or delayed sowings are not good as the flowering time may coincide with rains leading to grain mold incidence in the former case and moisture stress in the later.
Late sown crop is also susceptible to the infestation of shoot fly and midge. Moreover, extra early sowing during April/May results in synthesis of dhurin by plant roots which is translocated to stem and leaves in the form of hydrocyanic acid (HCN) which is highly poisonous, if fed to cattle.
Rabi sorghum is grown in the states of Maharashtra and Karnataka. In Andhra Pradesh, it is called Maghi season. The optimum time of sowing of rabi sorghum under rainfed conditions is second fortnight of September to mid-October. Under irrigated conditions, as in Dharwad (Karnataka), sowings can be delayed and second week of October is the optimum time.
For Maghi season of Andhra Pradesh, last week of September to first week of October is ideal time of its sowing. For summer cultivation in the states of Tamil Nadu, Andhra Pradesh and Karnataka, January-February is the optimum sowing time under irrigated conditions.
Seed Rate and Spacing:
Seed rate mainly depends on the stature of the cultivars and its duration. The optimum plant density in any sorghum growing region is depends on the available moisture, fertility status of soil and vigour of the particular variety.
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. Since the farmers generally drill behind the plough, it becomes difficult to maintain uniform distance between the plants. This limitation can be overcome by thinning out the excess seedlings. 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.
However, under assured soil moisture conditions, higher yields could be obtained with 1.80 lakh plants. A row spacing of 40 or 60 cm is optimum in rabi provided the requisite population is maintained. Available soil moisture conditions also influence the planting pattern. Under adequate moisture conditions, narrow rows should be preferred whereas under limited moisture conditions, the rows should be widely spaced.
Generally the plant population is reduced to cope with the soil moisture deficiency. This could be effected either by increasing row spacing or spacing within the row. The best alternative is to space the plants more closely within the row and to increase the distance between rows.
Under wide rows, the soil moisture supply is not exhausted as rapidly as in narrow rows. Intra-row competition prevents excessive vegetative growth, and the laterally developing roots have to grow farther to reach moisture. A seed rate of 8-10 kg/ha is required to obtain required plant populations. Generally, the seed is sown to a depth of 3-4 cm. After germination, plants in the rows are thinned at the desired spacing.
Seed Treatment:
A healthy crop with good yields starts with the use of well selected seeds for sowing. To get the required plant stand, healthy and good ear-heads with well-filled seeds need to be selected at the time of harvesting. Seed from such ear-heads are stored in a well-ventilated with low moisture conditions. Use certified quality seeds of hybrids and improved varieties recommended for the area.
The seed should be treated with appropriate chemicals prior to planting to prevent seed- borne diseases as well as soil pests which are common in the field during the earlier years. The seeds are also treated with some bio-fertilizers for easy and enhanced availability of important nutrients like nitrogen and phosphorus. Seed hardening is also practiced for better germination.
The following are the seed treatment practices:
1. Seed hardening is done by soaking the seeds in 2% (20 g in one liter of water) potassium dihydrogen phosphate solution for 6 hours. Use 350 ml of solution for soaking one kg of seed.
2. Dry the seed in shade to original moisture level.
3. The seeds of sorghum are treated with the 300 mesh Sulfur powder @ 4 gm of sulfur per kg of seeds for controlling the smut disease.
4. The seeds are soaked in 30% salt solution (3 kg of common salt in 10 liters of water). Ergot affected seeds which float are removed to avoid the incidence of ergot disease.
5. Seeds are treated with Carbofuran to prevent shoot fly infestation.
6. Treat the seeds with three packets each of Azospirillum (600 g) and Phosphobacterium to enhance the availability of nitrogen and phosphorus.
7. The seed treatment is done manually for small amount of seeds.
8. Large amount of seeds can be treated using a seed treating drum.
Method of Sowing:
The seeds are sown either by broadcasting seed manually, sowing behind country plough using pora, using an improved seed drill which may or may not be fitted with hoppers for fertilizer application and using mechanical seed drills attached to a tractor.
In broadcasting, the germination may not be uniform and higher seed rate is required to get the optimum plant stand in the field. Line sowing is done using a country seed drill called pora i.e., a wooden hopper attached to a hollow bamboo. It is used to sow the seeds in the shallow furrows opened by the tines of a country plough.
Mechanical seed drill or seed-cum-fertilizer drill is also used to cover the large area. In northern parts of India, sorghum is normally sown either by broadcast method or in lines behind the plough. The seeds of hybrids and improved varieties should always be sown in rows for obtaining higher yields.
Sowing in rows is common in black cotton soils. Sorghum is a tall growing crop, and to avoid mutual shading, the direction of rows should be kept facing the sun (sun rise and sun set direction) so that sun rays can penetrate even to the lower leaves and help the plants in better photosynthesis and carbohydrate manufacture.
Under rainfed conditions, paired row planting pattern has been found promising. The paired row planting systems include 30/60 cm and 45/90 cm. Sowing sorghum in ridge and furrow system is beneficial in low rainfall areas.
When seeds are sown using ridge and furrow system, the seeds are either sown at the bottom of the furrow or on the side or top of the ridge.
Planting on the side or top of the ride is practiced in heavy rainfall areas and under irrigated conditions. The broad-bed and furrow (BBF) system has an advantage over flat sowing in – Draining off excess water, providing more soil aeration for plant growth, greater in- situ moisture conservation and easier for weeding and mechanical harvesting.
Crust formation at the time of crop emergence is a problem in maintaining optimum plant stand, especially in sandy loam light soils having 50-70% sand, 30-50% silt and 20% clay. Crust is a hard layer formed on soil surface by the beating action of falling rain drops. The problem of crust formation occurs when there are rains after sowing sorghum before emergence. Sorghum seedlings fail to emerge because of hard surface soil.
Thinning:
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.
6. Manures and Fertilizer Required for Sorghum Cultivation:
Prior to the availability of improved varieties and sorghum hybrids, very little fertilizers were used with consequent low sorghum yields. With the cultivation of high yielding varieties and hybrids, fertilizer application is essential to get the yield potential of these cultivars. Sorghum is a nutrient exhaustive crop. 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. As against such a heavy removal of nutrients, the actual supply of these nutrients by the farmers in our country is very meager and sometimes nil. Thus, farmers are harvesting low yield.
The rate of fertilizer application to sorghum largely depends on fertility status of soil, moisture availability and varieties to be grown. A soil test is the most practical method of determining fertilizer needs of sorghum crop.
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.
For hybrids and high yielding varieties cultivated under irrigated conditions, the dose of FYM or compost needs to be doubled i.e., 12-15 tones/ha. Azospirillum, a bio-fertilizer, is recommended to at 2 kg/ha mixed with each of 25 kg of FYM and soil, and applied at the final ploughing or at sowing.
Sorghum responds profitably to a balanced fertilizer application program. Soil testing to know about the nutrient availability is the first step towards balanced fertilizer program that do not waste fertilizer by applying nutrients that are already sufficient for the anticipated level of production.
Balanced fertility program improves water use efficiency, drought-tolerance, and grain yield at the lowest possible cost. Fertilizer requirement of hybrid/composite varieties of sorghum is higher than desi cultivars. Response to nitrogen by kharif sorghum varies from 10-13 kg grain Ag N. In general, 40-60 kg N/ha and 20-30 kg P2O5 and 10-20 kg K2O/ha is recommended for rainfed areas, while 80-100 kg N, 30-40 kg P2O5 and 25-30 kg K2O/ha should be supplied under irrigated conditions.
The response to K fertilization in India is rare due to high K content of sorghum soils. However, said quantity should be given to balance the fertilizer application. For hybrids and fertilizer responsive varieties like CSH 13 R, CSH 15 R, and Swati, 100-120 kg N/ha is beneficial under irrigated condition.
Method of Fertilizer Application:
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. The remaining amount of N should be given again in shallow furrows 50-60 DAS or at booting stage of the crop. Avoid third top dressing of N, if soil moisture is scarce.
Use of Micronutrients:
The deficiency of zinc and iron (in calcareous soils) is increasing day by day. Soil application of 20-25 kg zinc sulphate once in 3 years as basal along with other fertilizers or foliar spray of 0.2% zinc sulphate with half quantity of lime to prevent burning of leaves is promising in zinc deficient soils. Sorghum is sensitive to iron deficiency. In case of iron deficiency, foliar spray of 0.1% ferrous sulphate with lime is recommended to overcome the deficiency.
Bio-Fertilizers and Organic Manuring:
Seed inoculation with Azotobacter chrooccum or Azospirillum lipoferum or A. brasilense has been found effective in saving 10-20 kg/ha N under rainfed conditions. Application of 5 tonnes FYM with recommended dose of fertilizers improves soil health and uptake of nutrients during kharif season.
Higher yield increments were obtained (up to 35-45 %), when mineral fertilizers were applied together with manure. Application of 3 tonnes/ha FYM + 75% of recommended dose of fertilizers + treatment of seeds with Azospirillum in rabi sorghum results in higher yield equivalent to 100% recommended dose of chemical fertilizers.
7. Water Management for Sorghum Cultivation:
Sorghum is predominantly grown as rainfed crop in kharif, and on conserved moisture in rabi. It is a drought tolerant crop because of its extensive and deep root system capable of extracting moisture soil moisture from deeper soil layers. 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). Summer jowar is grown exclusively under irrigation. To produce one kilogram of dry matter, sorghum consumes 291 kilogram of water, while under the same conditions maize uses 336 kilograms.
Depending upon availability of water resources for irrigation, jowar is provided with protective irrigation in kharif and is grown as irrigated crop in rabi. There are four critical stages of irrigation i.e., flower primordial initiation (25-30 DAS), flag leaf stage (50-55 DAS), flowering (60-70 DAS) and grain filling (80-90 DAS).
Under adequate water supply conditions of rabi and summer, irrigation should be given at all these critical stages. If water is available for 2 irrigations only, these should be applied at flower primordial initiation and flowering stages. In kharif rainfed crop, with prolonged dry spells, irrigation should be given at these critical stages.
The irrigation water requirement of summer sorghum is the highest (500-700 mm) followed by rabi (240-350 mm) and the least in kharif (120-250 mm). Similarly deep soils (vertisols) require less water than light soils (sandy, red soils). Drooping and withering of leaves during morning period and or cracking of the soil surface of the field.
Irrigation scheduling at 75 % depletion of available soil moisture (DASM) in plough depths during kharif and at 5-0 % DASM in rabi and summer is optimum for jowar. For scheduling irrigation based on irrigation water/cumulative pan evaporation (IW/CPE) ratio, 0.4 in kharif, and 0.8-1.0 in rabi and summer is ideal. Sorghum crop is usually irrigated by check basin or border methods of surface irrigation.
In rainfed kharif and rabi jowar, moisture conservation is extremely important. The crop sown in ridge and furrow or flat sowing followed by ridging 30-35 DAS has; been found effective in moisture conservation during kharif.
Irrigation for a Ratoon Crop:
Irrigate immediately after cutting the main crop. Irrigation should not be delayed for more than 24 hours after cutting. Irrigate on 3rd or 4th day after cutting. Subsequently irrigate once in 7-10 days. Stop irrigation on 70-80 days after ratooning.
Organic mulching with crop residues or removal of weeds and vertical mulching by digging trenches of 30-40 cm of 15-20 cm width are other effective methods of in situ moisture conservation practices recommended for successful jowar cultivation under rainfed conditions. Use of antitranspirants and reflectants may aid in reducing transpirational losses of water.
8. Weed Management for Sorghum Cultivation:
Weeds simultaneously germinate in the crop sown under kharif rainfed conditions and cause severe competition with crop. The initial 30-45 days after sowing is the critical period of crop-weed competition. The crop should be kept weed free during this period. This is achieved by manual weeding and hoeing in rabi and zaid seasons. During kharif season, intermittent rains may not permit weeding and hoeing. Weeds may cause 20-60% reduction in yield, if not controlled at right time.
During kharif season both grassy and broad-leaved weeds grow with sorghum crop. These are – Echinochloa colonum, E. crusgalli (sawan), Dactyloctenium aegypticum (makra), Eleusine indica (kodo), Setaria glauca (bandar-bandri), Cyperus rotundus (motha), Sorghum halepanse (banchari), Cynodon dactylon (doob), and Phragnutes kakta (narkul).
Off-season tillage (harrowing or deep ploughing in summer) can considerably bring down the weed population leading to optimum sorghum yield. Weeds may be removed with the help of khurpi or hand hoe. Normally two hand weedings at 15 and 30 DAS, effectively control the weeds in sorghum.
Inter row weeds may be controlled mechanically by running blade harrow. Both inter and intra row weeds can be controlled effectively by using herbicides. Spraying of atrazine or oxadiazon @ 0.75-1.0 kg/ha dissolved in 800-1000 litres of water as pre-emergence just after sowing could successfully control the weeds. There should be enough moisture in the soil at the time of spraying.
Intercropping with cowpea has also been found effective in weed management. 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. Crop rotation with trap crops such as cotton, soybean, pigeon pea and groundnut, destroyed the seeds and minimize the losses. If striga menace is severe, spraying of 2, 4-D sodium salt as post-emergence @ 1 kg/ha between 20-60 DAS, is recommended in addition to above herbicides.
9. Cropping Systems of Sorghum:
Sorghum based cropping system include mixed cropping, intercropping and double cropping. Intercropping cropping is aimed to optimize production to make the best of aberrant weather situations. It is widely practiced in dryland/rainfed areas and sorghum crop is one of the most important component in these areas because of substantial yield advantages as well as greater stability in the yields. Cereal/legume combination is ideal for intercropping.
Inter cropping of soybean, pigeonpea, blackgram, greengram and cowpea with sorghum has been found profitable in north India. Results of experiments conducted under AiCSIP, revealed that hybrids are, in general, superior for intercropping. Sorghum hybrid CSH 1 and CSH 6 are more suitable under low rainfall and on light soils while CSH 5 and CSH 9 are better adopted under high rainfall and medium to heavy soils. Planting geometry and planting densities are crucial.
At Indore (MP) and Surat (Gujarat) intercropping of sorghum (CSH 9) + pigeon pea at 4:2 row ratio was found to be the best. Most of the high yielding varieties and hybrids mature in about 90-120 days, and fit well in multiple crop rotations.
10. Special Practices for Sorghum:
There are some special practices followed in certain sorghum growing areas.
Some of the practices are:
i. Transplanting:
The transplanting of young sorghum seedlings is practiced in Tamil Nadu under irrigated conditions. An area of 300 m2 is required for raising nursery which is sufficient for transplanting in 1 ha.
ii. Seed Hardening:
Pre sowing seed hardening helps in modifying physiological and biochemical nature of seeds to enhance drought tolerance and ensures high germination rate. Soaking of sorghum seeds in 1.0 % CaCl2 is found beneficial. Similarly, sorghum seeds are presoaked in 2 % solution of potassium hydrogen phosphate (KH2PO4) for 6 hour in equal volume and then dried, back to original moisture content in shade and then sowing is done.
iii. Ratooning:
Ratooning is common practice in multi cut varieties of forage sorghum. This practice is also followed in grain sorghum and ratoon crop of hybrid sorghum gives as much yield as plant crop. Ratooning can be adopted wherever irrigation facilities are available. Some of the sorghum hybrids like CSH 1 and CSH 5 have good rationing ability.
Among the improved varieties, SPV 351 and SPV 462 are found to have good rationing ability. Higher plant population (2 lakh/ha) 120 kg N/ha to plant crop are advantageous for ratoon cultivation. For ratooning all the plants in the field is harvested at one time while the stem is green.
It is desirable to maintain a cutting height of about 8-10 cm above ground level, as it retains sufficient carbohydrates in the stubbles. The second day after harvesting, an irrigation is given to induce sprouting from the nodes.
Fertilizer at the rate of 60 kg N/ha should be applied. Half of the N should be applied at the base of stubble and covered before the first irrigation. Sorghum stubble produces a number of sprouts. The weak sprouts should be thinned leaving 2-3 good healthy sprouts in each of the stubble. The remaining ½ of the N should be applied within 30 days from the date of ratooning.
Optimum moisture should be maintained from boot leaf stage to grain hardening stage. Plant protection measures should be taken in time against pests and diseases as in plant crop. Though, the ear-head size in ratoon crop is smaller as compared with plant crop because 2-3 sprouts emerges from each stubbles, but yield of grain per hectare is almost same or higher than plant crop.
Ratoon crop is ready for harvest in about 80-85 days. Ratooning is beneficial under rainfed conditions with good rainfall and under irrigated conditions, where plant a fodder crop, a ratoon grain crop is desired in summer.
11. Drought Mitigation in Sorghum through Contingency Planning:
(a) Kharif Sorghum:
Early Onset of Monsoon:
Sowing with the onset of monsoon is recommended for assured high yields.
Early Onset of Monsoon followed by a Long Gap:
Repeated inter-cultivation operations like hoeing, weeding and mulching are suggested to conserve moisture. Under severe moisture stress, reduce the plant population by 2/3 by thinning for judicious use of moisture. Limited plant population assures normal growth of the crop.
Secondly, sporadic break out of Army worms is expected under such situation. A poisonous bait consisting of 250 ml of Metacystox + 4 Kg of rice bran mixed with 8 litres of water shall be sprinkled in the field as a bait. This will effectively control both Moths and the Larvae. This practice is widely used in Karnataka.
Delayed Onset of Monsoon:
In case there is delay in monsoon by 2-3 weeks, short duration cultivars such as CSH 6 and CSH 14 can be preferred. Increase seed rate to an extent of 1.5 times of the recommended rate and apply 20 Kg of Carbofuran or Phorate 3 g, granules in the seed rows before sowing to safe guard against the shoot fly attack. Other shoot fly control measures (spraying of Endosulfan 2ml/litre of water after sowing) can also be followed if soil application is not adopted.
Prolonged Monsoon and Excessive Rainfall at Maturity:
These situations at seed development stage are likely to cause heavy grain mold infestation. Harvesting of the crop at physiological maturity to avoid damage by grain mold and alternatively spraying fungicidal mixture containing 0.3% Dithane M-45 three times at 10 days interval starting from 50% flowering and onwards are recommended.
Failure of Monsoon:
If monsoon fails after sowing of the crop, plant population should be reduced proportionately to 1/2 either by uprooting alternate plants or alternate rows. However, in case of partial failure and extremely delayed monsoon alternative crops like castor, bajra and horse gram may be sown in light soils.
(b) Rabi Sorghum:
Delayed termination of monsoon: This situation is welcome to rabi sorghum. If resistant varieties are not planted, protect the crop from the Shoot fly infestation by applying granules before sowing as a precautionary measure.
In order to ensure grain production under severe drought, thin out alternate rows so that available moisture can support the retained plants.
12. Harvesting, Threshing and Yielding of Sorghum:
The crop should be harvested immediately after maturity to minimize the losses due to birds, insects, mold, and bad weather. There is no need to wait for stalks and leaves to dry as the plants of hybrid sorghum appear green even after the crop maturity.
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.
In other method, earheads only are removed from the standing crop and collected at the threshing floor for threshing after 3-4 days of sun-drying. The standing stalks, depending on the convenience, will be cut at ground level for feeding the cattle. Harvested ear heads are dried in sun for 1-2 days or until the grain moisture content drops down to 12 per cent.
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.
Yields:
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 called ‘ dhurrin’. In the stomach of animals dhurrin is converted into hydrocyanic acid (HCN). Thus, when young plants (about 5 kg) are fed to catties, it causes carcinogenic death. This is known as prussic acid poisoning or sorghum poisoning. The HCN content gets diluted as the age advances.
Young leaves and high N applied crop contains more HCN. Its content in leaf is 3-25 times greater than stalks. Toxic limit of prussic acid is >200ppm. After flowering/heading HCN content reduces to safe level for feeding to the animals.
As first aid treatments, affected animals may be given intravenous injection of sodium thiosulphate to restore capability of oxygen transport of blood. Moreover, two full drenches of mollases may be given to provide extra energy to affected animals.
The after effects of sorghum roots and stubbles on succeeding crop of sorghum is called as ‘sorghum injury’. This condition lasts for few months or until the sorghum residues decay. Sorghum stubbles, being more fibrous, take longer time to decompose than other cereals.
During the process of decomposition they retain or remove considerable moisture. While decaying lots of microbes are build up (due to more sugar content in stalks) and they temporarily lockup N. Sorghum injury can be overcome by providing additional N or green manuring. Growing of sorghum immediately should be avoided.
13. Varieties of Sorghum:
Traditional varieties of sorghum grown in various states are of long duration with poor yield potential. Improved varieties and hybrids produced higher yield than traditional varieties. A good number of high yielding varieties and hybrids have been developed in sorghum both for cultivation in kharif and rabi seasons.
An ideal cultivar is one that combines yield and stability of performance. Kharif cultivars are essential to be of short duration, short stature and photo-insensitive to ward off grain mould infestation.
The rabi (post-rainy) cultivars, on the other hand, should be tall, temperature insensitive with high degree of terminal drought tolerance, photo-insensitive besides having resistance to charcol rot and lodging. The first sorghum hybrid CSH-1 was released in 1964 and the improved variety CSV-1 (Swarna) in 1968.