In this article we will discuss about the sorghum based cropping systems in India.
The area under Man/sorghum is highest in Maharashtra followed by Madhya Pradesh. On all India basis, about 17 major cropping systems have been identified. In Maharashtra, cotton, pulses, groundnut and small millets are grown as alternate crops to kharif sorghum, depending on the onset of monsoon.
In Madhya Pradesh, besides the above crops, wheat and fodders are sown. In Rajasthan, wheat, cotton, pearlmillet are grown in kharif sorghum tracts. In Andhra Pradesh, groundnut, cotton, pulses and oilseeds are alternated with sorghum. Fingermillet is the major alternate crop to sorghum in Karnataka.
In dryland agriculture, the chances of yearly two crops systems are limited especially when kharif sorghum is grown on light soils with low soil moisture retentivity. As such, sorghum based systems are yearly based than season-based systems every year.
Sorghum-wheat, sorghum-cotton, sorghum-groundnut, sorghum-pearlmillet, sorghum-fingermillet, sorghum-bengalgram and sorghum- pulses are some of the major systems. If sorghum is grown on stored soil moisture during postrainy season, short duration pulses or fodders are grown before the sorghum crop.
1. Intercroping System:
With particular reference to dryland agriculture, intercropping is aimed at crop insurance against unpredictable weather during the crop season. In the case of normal rainfall with an ideal distribution, intercropping system as a whole should prove to be more profitable than growing either of the component crops alone.
Sorghum is most commonly intercropping with pigeonpea in India. Simultaneous planting of crops during monsoon (June-July) with higher proportion of sorghum than pigeonpea is the usual practice. However, experimental results indicate higher pigeonpea yield with higher proportion with little or no reduction in sorghum yield.
Sorghum two rows, with 45 cm row spacing, followed by one row of pigonpea (2:1) can accommodate optimum sole crop populations of both the crops (1,00,000 sorghum and 40,000-50,000 pigeonpea) for an overall yield advantage of about 60 per cent. On light soils, the advantage of intercropping is less (30-50%) than that on heavy soils because of less residual soil moisture in postrainy season for pigeonpea.
Paired row planting can accommodate full population of both the component crops. Normal planting method for sorghum is in 45 cm rows with about 12 cm between plants in the row to accommodate around 1,80,000 plants ha-1. In paired row method, a pair of sorghum rows is 60 cm with 12 cm between plants in the row.
In this way, plant population of 1,80,000 ha-1 is maintained for the sorghum crop. In the interspace of 60 cm, one row of pigeonpea or two or more rows of other short statured intercrops can be planted. From several studies, it appears that yield of tall component is usually less affected by component plant densities and manipulation of spacing between component crops. Low canopy component crop yield is usually reduced, however, depending on the proximity of the tall growing component.
Studies on intercropping system under AICSIP for identifying compatible crops as intercrops with sorghum indicated the following crops for different regions:
At all the centers, these intercrops have increased the gross returns considerably over sorghum alone. Highest returns of soybean, greengram and groundnut as intercrops with sorghum were obtained with sorghum in paired rows (30/90 cm) with two rows of intercrops in 90 cm space. Next in the order was sorghum in equidistant rows (60 cm) with one row of intercrop in between two rows.
2. Sequence Cropping System:
Southern districts of Rajasthan, most part of eastern Madhya Pradesh, Vidarbha region of Maharashtra and some parts of Andhra Pradesh receive 700-800 mm rainfall and have moisture retentive black soils.
Traditionally, these areas grow single long duration kharif sorghum either during the monsoon or post-monsoon period. Introduction of short duration sorghum hybrids and other pulse or oilseed crops considerably improve the scope for sequential cropping in such areas.
However, sequential cropping is not gaining importance due to several reasons for cropping in monsoon on heavy soils:
1. Wet soil becomes too sticky and difficult for preparatory tillage and sowing.
2. Heavy weed infestation since the moist soil does not allow either manual weeding or intercultivation with implements.
3. Crop damage due to waterlogging.
4. Harvesting problems of rainy season crops due to frequent rains during October-November.
Results of experiments to identify the best sorghum based sequence indicated the following:
1. Kharif sorghum proved more remunerative than mid-season or rabi sorghum at all the locations.
2. At all the three centers (Parbhani, Dharwad and Rajendranagar), possibility of double cropping was clearly established. A crop after kharif sorghum proved more economical than a crop in kharif and sorghum in either rabi or early rabi.
3. Among the crops after kharif sorghum, highest returns were due to safflower followed by sunflower and bengalgram.
4. Sorghum-safflower and sorghum-bengalgram were more remunerative at Indore and Udaipur. Sorghum-mustard was also equally remunerative at Udaipur.
3. Ratoon Cropping System:
Ratoon cropping is an old system, which has been practiced for many years, especially in tropics. The first harvest is usually called plant crop and each subsequent harvest is designated as first ratoon, second ratoon etc.
Ratooning sorghum for fodder and grain has been successful in India. Harvest time of plant crop, cutting height of stubble, tillers per culm, moisture and nutrients affect the ratoon growth. There are two system of ratooning. In the first system, sorghum is grown for fodder under irrigation in summer and the ratoon maintained for grain in the following rainy season.
The earlier maturing ratoon grain crop gives greater opportunity to plant in time the postrainy season crops to avoid terminal soil moisture stress. The second system that utilise the ratoon concept is harvesting rainy season sorghum for fodder at 40-50 days and ratoon crop for grain.
This has the advantage of reducing the effect of mid-season drought and prolonging the cropping season to produce quality grain in dry weather. Major drawback of ratooning sorghum in India is severe incidence of shootfly, which attacks the young shoots.
Results of experiments on management of sorghum ratoon at Rajendranagar and Parbhani indicated that ratooning proved more remunerative than plant crop. Grain yield by maintaining three tillers per stubble was higher than one and two tillers. Ratoon crop on light soils was more remunerative than kharif plant crop, if two irrigations are given, on each at flowering and grain development with 40 kg N ha-1.
Effect of Sorghum on Succeeding Crop:
Sorghum leaves toxic residues in soil and the crop following it usually suffer from toxic residues. This adverse effect is known as sorghum effect in India. The main reason for any negative effect is probably the large amount of residues left in on the soil after sorghum harvest. These residues have wide C/N ratio.
When the residue ploughed into the soil start decomposition, the soil microbes rapidly utilise the limited available nitrogen for their multiplication. As such, shortage of nitrogen affects the succeeding crop. This negative effect is only for a short period and disappears when once the residues have been decomposed. Such condition can be largely overcome by applying nitrogen fertilisers to crops that follow sorghum.