In this essay we will discuss about:- 1. Origin and Distribution of Sorghum 2. Area and Production of Sorghum 3. Nutrient Management 4. Tillage and Seeding 5. Weed Management 6. Transplanted Sorghum.
Sorghum (Sorghum bicolor), also known in India as jowar, on worldwide basis rank fourth among major cereals after wheat, rice and maize in area and production. It is the major cereal crop of dryad agriculture in semiarid tropics. Sorghum grain is the basic food in parts of Asia and Africa, while in Europe and North America it is mainly used as feed for poultry and livestock.
Sorghum stem with leaves (green fodder, silage, straw) is used for feeding the animals in much sorghum growing Asian countries. In the past, sorghum used to be a crop in regions with climates that were too dry and hoi for maize. With the advent of hybrids, sorghum is well competing with maize even under more favourable conditions and under irrigation.
Origin and Distribution of Sorghum:
Sorghum (guinea corn) characterised by a tremendous amount of morphological variability is leading to dispute even in the area of greatest diversity. Vovilov placed its origin in the northeast Africa, while Doggett, (1970) placed its origin in the Indo-Malaysian area. There is evidence of sorghum in Assyria by 700 BC and in India and Europe by first AD.
Domestication of sorghum is believed to have commenced in the area comprising Ethiopia and Egypt around 3000 BC. However De Wet (1970) suggested a diverse origin of domesticated sorghum, with S.verticilliflorum as the possible progenitor.
It is often accepted that the races of durra, guinea and caffra were derived from S.aethiopicum, S.arundinaceum and S.verticilliflorum respectively, as progenitors. Caffra is common in southern central (Bantu) Africa, Caudatums in central Sudan and Guinea in West Africa.
Sorghum probably moved out of Africa to India and China through sailing ships. Evidence suggests that sorghum was established in India before the time of Christ but not earlier than 1500 BC. Cultivated sorghums were first introduced to America and Australia about 100 years ago.
Sorghum was introduced into the Middle East and Mediterranean areas from Ethiopia and Egypt. The major sorghum producing areas today include the Great Plains of North America, Sub-Saharan Africa, northeastern China, Deccan Plateau of India, Argentina, Nigeria, Egypt and Mexico. The USSR, France and Spain are the leading sorghum producing countries in Europe.
The International Crops Research Institute for Semiarid Tropics (ICRISAT) at Hyderabad, India is the major germplasm collection centre and serve to disseminate sorghum accessions all over the world. The National Centre for Sorghum at Hyderabad in India and one at Ahmadu Bello University, Zaria, Nigeria are the national germplasm repositories.
Over 90 per cent of the Indian sorghum is grown between 12° and 26°N and 72° and 80°NE comprising central and Peninsular India. African sorghum is grown between 10° and 23°S and 15° and 35°E longitudes. The average temperature range in sorghum areas is between 27° and 35°C. The crop season on an average receive around 600 mm rainfall.
Area and Production of Sorghum:
Sorghum is cultivated as a major food crop in much of South Asia, Africa and Central America. In USA, Australia and South America, sorghum is grown mainly for animal feed. Sorghum is adapted to warm and dry climate and largely cultivated in drought prone areas of the world. In these areas, sorghum is usually grown with limited inputs in conditions of sparse rainfall and low soil fertility, with poor yields.
Lower average yields are primarily a result of the hot, dry conditions where sorghum is mostly grown, rather than sorghum plant’s capability. In fact, sorghum has high yield potential, comparable to rice, wheat and maize. On a field basis, sorghum yields have exceeded 11.0 t ha-1, with above average yields ranging from 7.0 to 9.0 t ha-1 where moisture is not a limiting factor. In areas where sorghum is commonly grown, yields of 3.0 to 4.0 t ha-1 are obtained under better conditions, dropping down to 300 to 1000 kg ha-1 as moisture and soil fertility become limiting.
A majority of the subsistence farmers who typically cultivate this crop are unable to take advantage of high yield potential because they have limited options for improving their management practices. Hence, sorghum production can be achieved through growing verities/hybrids with improved tolerance to drought and low soil fertility and resistance to pests and diseases.
World production of sorghum cereal grain in 2005-06 was 58.9 M t, the production being stable over a long period of time.
Major global producers of sorghum (2005-06) are given below:
United States of America (9.8 M t)
Nigeria (8.3 M t)
India (8.0 M t)
Mexico (6.3 M t)
Sudan (4.2 M t)
Argentina (2.9 M t)
China (3.0 M t)
Ethiopia (1.8 M t)
Australia (1.7 Mt)
Brazil (1.5 Mt).
India has ever been among the major producers of sorghum in the world. The country has been able to maintain its position among the top three producers of the crop. Sorghum is produced both as kharif and rabi crops in the country.
Indian production hovers around an average of 8.0 M t but since last few years a slow downfall in the production as well as in the area covered for sorghum production has been observed. Area wise, India accounts for around 20 per cent of the world total area under sorghum.
The 2008-09 Indian sorghum production figures were 7.25 M t from an area of 7.5 M ha with a productivity of 962 kg ha-1. The major states producing sorghum in India are: Maharashtra, Karnataka, Gujarat, MP, AP, Rajasthan and UP.
Maharashtra ranks first both in area (4.01 M ha) and production (3.59 M t) of sorghum followed by Karnataka with an area of 1.38 M ha and production 1.63 M t. Highest yield is in AP (1563 kg ha-1) followed by Karnataka (1179 kg-1).
Nutrient Management for Sorghum:
Development of better adapted high yielding cultivars increased the yield potential of sorghum. This increased yield potential requires more plant nutrients. Consequently, fertiliser application to sorghum has increased tremendously, especially under the conditions of no soil moisture stress during the crop growing season. Nitrogen and phosphorus fertilisers are used in relatively large quantities.
Nutrient Concentration:
Knowledge of tissue nutrient concentrations necessary for optimum growth rate is needed to diagnose nutrient deficiencies. Lockman (1972) provided a useful description of adequate nutritional ranges for several nutrients in grain sorghum tissues at different growth stages.
Nitrogen and phosphorus concentrations are well correlated with yield at all growth stages. Potassium levels with grain yield only for seedling and vegetative samples. Zinc levels in grain sorghum plant samples showed curvilinear correlations with grain yield.
Other essential nutrient concentrations in plant samples are not well correlated with grain yield. Deficient, low and adequate values for grain sorghum N, P and K concentrations at different growth stages are presented in Table 5.6.
TABLE 5.6: Nutrient concentrations (g kg-1) in sorghum plant.
Nutrient Uptake:
One general guideline for nutrient needs is the nutrient removal by the crop. Large quantities of nitrogen and phosphorus and some potassium are translocated from plant parts to the grain as it develops. Unless adequate nutrients are available during grain filling, this translocation may cause deficiencies in the leaves and premature leaf loss, which reduce leaf area duration and may decrease yields. Thus, adequate supply of nutrients at all stages of development of the plant is necessary for maximum yields.
A large portion of the nitrogen and phosphorus but only a small portion of potassium is removed in the grain. According to Vanderlip (1972), a grain crop of 8500 kg ha-1 contains 207 N, 39 P and 241 K kg ha-1. If the entire plant is harvested for silage or other forms of feed, much more potassium is removed because most of it is in the vegetative part of the plant.
During the initial 4-5 weeks, average daily nitrogen uptake is about 1.5 to 2.0 kg ha-1. It increases to a maximum daily uptake of 6 kg ha-1 during the 20 days period preceding the boot stage. Highest uptake of 180 kg N ha-1 is expected at soft dough stage. Phosphorus uptake of sorghum appears to be similar to that of nitrogen, except that phosphorus uptake continues into the grain filling stage, while nitrogen uptake tends to decrease in the later stages.
Out of about 60 kg P2O5 ha-1 uptake, nearly 80 per cent is found in grain. Potassium uptake is higher in the early part of the season than that of either nitrogen or phosphorus. Highest uptake of 135 kg K2O ha-1 has been reported. However, it decreases during the last seven days of the growing season.
Summarising the results of many workers, it has been concluded that a grain sorghum crop yielding 5000 to 6000 kg ha-1 removes about 130-180, 50-65 and 100-150 N, P2O5 and K2O kg ha-1 respectively. Out of this, only 60-70, 70-80 and 25-30 per cent NPK, respectively are retained in the grain.
Tillage and Seeding of Sorghum Cultivation:
Sorghum cultivation still remains predominantly traditional in most part of the country. Its area is progressively decreasing because of reducing demand for sorghum grain, no incentive to fanner and government policies.
Preparatory Tillage and Intercultivation:
Since sorghum is cultivated in rotation with a large variety of crops, nature of preparatory tillage varies with preceding crops. For kharif sorghum on light soils, land is ploughed twice and harrowed before sowing. If sorghum is grown after groundnut, no ploughing is given except 2 to 3 harrowings. For rabi sorghum on deep black soils, the land is harrowed periodically to conserve rain water and to check weed growth.
Sorghum seed is, generally, drilled with a row spacing around 30-45 cm. Interculturing with bullock drawn implements continue to be practiced and are very relevant even today. However, tractor drawn implements fabricated to meet the local needs have replaced bullock drawn implements for land preparation.
Seed Rate, Spacing and Plant Population:
Seed rate largely depends on the stature of the cultivar and its duration. In general, varieties require lesser seed rate than the hybrid sorghums. A seed rate of 10-12 kg ha-1 appears to be optimum for hybrids as against 8-10 kg ha-1 for varieties. Sorghum is usually sown in rows using seed drills. Results of experiments in sorghum tracts of the country (Table 5.4) indicate significant variation in grain yield due to different row spacings.
TABLE 5.4: Effect of row spacing on grain yield (kg ha-1) of kharif sorghum.
In three of the four experiments, row spacing of 46 cm gave highest yield. Average grain yields for 23, 46 and 69 cm row spacing were 3400, 3490 and 3240 kg ha-1, respectively.
Significant response to varying plant populations was observed in 4 of the nine experiments (Table 5.5). Low population of 90,000 plants ha-1 recorded lowest yield. A population of 135,000 ha-1 was equal or better than highest population in three locations.
TABLE 5.5: Effect of plant population on grain (kg ha-1) of kharif sorghum.
Average grain yields with 90,000, 135,000 and 270,000 plants ha-1 were 2980, 3530 and 3690 kg ha-1. Relatively higher plant population has been suggested for hybrid sorghum compared with tall varieties for realising higher yields.
Based on several such studies the ICAR (2006) has recommended the following seed rates, spacing and plant populations for different cultivars in different seasons:
Recommendation for irrigated hybrids is same as that for kharif sorghums. For sorghums or receding soil moisture in postrainy season, plant population should be adjusted to match the amount of stored moisture in the soil profile. It is necessary to increase the row spacing and decrease the plant to plant distance in order to adjust for the level of stored moisture in the soil profile.
Sorghum crop can adjust to varying plant populations within the recommended ranges without significant variation in final grain yield. In general, when the final grain yield variations are not significant due to different plant population, it is advisable to go for higher plant population range for improving the palatability of straw as feed for cattle.
Weed Management for Sorghum:
The environment in which sorghum is grown also favours germination and growth of weeds. Sorghum crop is a poor competitor when young and weeds always have competitive edge.
The following weed species are usually associated with sorghum crop:
Weed seed germinate 2-3 days earlier than the sorghum seed since the weed seed will be in the soil, ideal for germination, before the sorghum seed is sown. Seedling growth of sorghum at the establishment is much slower than weed growth.
As such, the crop suffers most in the early stage. The critical period of crop weed competition is 15-35 days after sowing. Reduction in grain yield of sorghum due to weeds has been reported to vary from 15-40 per cent, depending on the intensity of infestation.
Cultural Management:
Off-season tillage (harrowing, deep ploughing) can considerably bring down the weed population leading to optimum sorghum yield. Deep ploughing could reduce the weed growth by 50 per cent at Hyderabad (AP) and increased the grain yield by 35 per cent. Since, row spacing for sorghum is wide enough for intercultivation, harrowing between the rows can minimise the weed problem.
However, hand weeding is necessary for intra-row weed control. Working blade harrow twice followed by one hand weeding resulted in grain yield of 2.5 t ha-1 as against 1.7 t h-1 with no harrowing and hand weeding. Off-season tillage, inter-row harrowing and hand weeding when judiciously combined, there may not be any necessity for chemical weed control.
Sorghum is, generally, grown on medium to deep soils with good water retentive capacity. As such, the soil is usually too wet to allow harrowing and manual hand weeding. Harrowing and other filed operations are often not possible when the crop is too tall to permit such operations. Hence, cultural operations early in the season are very essential.
Use of Herbicides:
When there is no scope for weed management through cultural methods, the following herbicides can effectively control the weeds in sorghum crop.
Striga litura (witch weed) is the common root parasite on sorghum. Stimulating germination of seed in the soil and destroying by tillage after they germinate can effectively control it. Crop ration with trap crops which produce chemical stimulant necessary for striga seed gennination but not parasitised by the witch weed and catch crops, which stimulate gennination but parasitised by the weed, offers effective control.
Soybean, cotton, cowpea, groundnut, chickpea and pigeonpea can be used as trap crops in rotation for controlling striga. Preplant soil incorporation (PPI) of Fenac or 2,3,6-TBA reduces parasitism by striga. PRE herbicides Simazine, Atrazine or Propazine can give effective control of this problem weed.
Transplanted Sorghum:
Transplanted sorghum crop, though not a common cropping practice in many sorghum areas, is practiced in certain parts of Tamil Nadu. There should be assured availability of water for raising a nursery and irrigating the transplanted sorghum crop.
Advantages of Transplanting:
Transplanted crop has the following advantages:
1. Main field duration is reduced by 10 days.
2. Optimum population can be maintained as only healthy seedlings are used for transplanting.
3. Seed rate can also be reduced by 2.5 kg ha-1.
4. Shoot fly, which attacks direct sown crops during the first 3 weeks and which is difficult to control can be effectively and economically controlled in the nursery itself.
5. Seedlings which show chlorotic and downy mildew symptoms can be eliminated; thereby incidence of downy mildew in the main field can be minimised.
Nursery:
Sorghum seedlings are raised in 7.5 cents (300 m2) near a water source, to plant one ha. About 750 kg of FYM or compost is applied in 7.5 cents nursery and another 500 kg of compost or FYM is applied for covering the seeds after sowing. The 300 m2 area is divided into 3 raised beds of 2.0 x 1.5 m with 30 cm space in between the beds.
Channels of 15 cm depth are formed around the beds for irrigation. Seed is covered by passing the hands lightly over the soil ensuring that the seeds are not sown deep as germination will be affected. The beds are irrigated to maintain adequate available soil moisture for optimum growth of the seedlings.
Main Field:
Ridges and furrows are formed 45 cm apart. Alternatively, form beds of size 10 m2 or 20 m2 depending on the availability of water. Irrigation channels are formed to evenly distribute water. Seedlings of 15 to 18 days are planted on the top of the ridges.
Seedlings of above 18 days will not establish properly or may die. About 1000 g ha-1 of Azospirillum inoculant is prepared in 40 liters of water and the root portion of the seedlings is dipped in this solution for 15-30 minutes before transplanting.
The seedlings are planted at 5 cm depth and 15 cm apart on the side of the ridge, half the distance from the top and bottom of the ridge.
Fertilisers are applied based on the soil test report. In the absence of soil test recommendations, a blanket recommendation of 90 N, 45 P2O5, 45 K2O kg ha-1 is adopted. Half the dose of nitrogen and full dose of P2O5, and K2O are applied before planting. The fertilisers are placed on two-thirds top side of the ridges at 5 cm depth and covered. The balance nitrogen dose is applied 15 days of planting and irrigated.