Most of the cultivated varieties of sorghum can be classified into a number of fairly distinct variety-groups, the most important of which are:
i. Kafir:
These are characterised by relatively small cylindrical heads, which are borne on strong juicy stalks. Leaves are large and relatively numerous. The seeds are medium sized.
ii. Milo:
These varieties have large, compact, ovoid heads, which are carried on slender dry stalks. This frequently results in recurred heads. The plants tiller freely, while the leaves are smaller and seeds are larger than those of kafirs. These are early maturing and more drought resistant than kafirs.
iii. Hegari:
It is similar to kafirs but more abundantly leafed and has more slender stalks.
iv. Feterita:
They have fairly compact, large heads born erect on slender dry stalks. They are sparsely leafed. Seeds are large, white and chalky and the inflorescence tends to shatter when ripe.
v. Durras:
They have beard, fuzzy heads, born on dry stalks. Heads are either open and erect or compact and curved. Seeds are large and mostly white.
vi. Shallus:
This group has loose heads borne on slender dry stalks with pearly-white seeds.
vii. Kaoliangs:
They have open bushy heads, dry slender slacks and small white or brown seeds.
There are a number of varieties, which bridge the gaps between Milo and Durra and between Durra and Feterita. These are closely related to Hegaris, which in turn are similar to the kafirs. There is no sharp delimitation between these last, with their juicy, sweet stalks and leafiness and the forage sorghums. Most traditional grain sorghums of India belong to Sorghum durra, S.cernuum and S.subglabrascens.
Traditional Varieties:
Natural selection and domestication over thousands of years have resulted in development of several varieties highly localised in their adaptation.
Notable among the varieties developed during early period and which are still under cultivation are:
Some of these improved varieties are still under cultivation, especially in kharif in many states due to their resistance to pests and diseases, superior grain quality, high straw and grain yield stability. The variety Maldandi (M 35-1) is still the ruling variety in Maharashtra, Karnataka and Andhra Pradesh during the post-rainy season, especially due to its superior grain quality, high fodder yield and stability in the productivity. Nandyal sorghum, N 13 is the international check for striga resistance studies. Several local varieties are popular as fodder sorghums.
High Yielding Hybrids and Varieties:
An ideal cultivar is one that combines yield and stability of performance. Stability assumes increased importance in rainfed sorghums due to rainfall variability. As a result of efforts under the accelerated hybrid sorghum project initiated by the ICAR during the year 1962, several hybrids and improved varieties were released for general cultivation. The first sorghum hybrid CSH 1 was released in 1964 and the improved variety Swarna in 1968.
Up to the year 2010, twenty-six sorghum hybrids (CSH 1 to CSH 26) and twenty-four improved varieties CSV 1 to CSV 216R, including SPV 96, SPV 462 and SPV 699 have been released by the ICAR. Besides these, several improved cultivars have been developed by SAUs and private seed industry.
Coincidence of grain development with continuous rains increased the incidence of grain moulds that largely nullified the yield advantage with high yielding sorghum cultivars. High yielding sorghum cultivars are also vulnerable to shoot fly, particularly under late sown conditions.
In rabi, recently developed CSV 18R and CSV 216R are giving good performance. However, their susceptibility to shoot fly, charcoal rot, low temperature induced sterility and poor grain quality limits their acceptance by the farming community. As such, M 35-1 is still the ruling variety in many sorghum tracts. Recommended sorghum cultivars for different states in kharif and rabi are given in Table 5.2.
TABLE 5.2 Improved cultivars recommended for major sorghum producing states.
More than 90 per cent of sorghum area is confined to rainy kharif and post rainy rabi. Only about 5 per cent is grown under irrigation during summer.
Based on soil type and onset of monsoon rains, states like Andhra Pradesh have more than three seasons as indicated below:
Kharif:
Light soils and relatively early onset of monsoon (June).
Early rabi (maghi):
Light to medium soils with considerable rainfall during northeast monsoon (September).
Rabi:
Deep soils with high soil moisture retentivity (October).
Late Ravi:
Medium to light soils receiving around 45 per cent of rainfall during northeast monsoon (November).
Summer sorghum:
Irrigated crop (January).
Optimum Time of Seeding:
At Nandyal (AP), highest yield of postrainy season sorghum on heavy soils can be obtained by sowing in mid-September instead of usual October sowing, mainly due to no terminal soil moisture stress and minimum shootfly damage. At Dharwad (Karnataka), also early June seeding is optimum than normal sowing. Seeding with the onset of monsoon is ideal at Indore (MP) than normal seeding in late June.
At Koilpatti (TN), April sowing results in highest yields of irrigated sorghum. Optimum period of sowing sorghum is onset of first monsoon rain and delays of 1,2 and 3 weeks lower the yields (Table 5.3) at a number of locations from 37 to 318 kg ha-1 day-1.
The rabi sorghum in Deccan sown in September gives 100 per cent more yield than October sowings. From the experiments conducted all over the country it is evident that the optimum time of sowing for sorghum is onset of monsoon (early June) for kharif, mid-September for post rainy season rabi and April for irrigated crop in summer. Yield advantage due to early seeding has been attributed to minimum pest and disease problems and avoidance of terminal soil moisture stress.
Concept of Dry Seeding:
In dryland agriculture, it may not be feasible to sow the crop in time if the onset of monsoon is delayed. If the land is prepared in time, taking advantage of summer rains, sowings can be taken up with the earliest monsoon rain. The other option is the concept of dry seeding based on probability of rainfall.
TABLE 5.3: Optimum time of sowing kharif sorghum.
Dry seeding is dome in anticipation of rain. It aids in establishment of crop at 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 Marathwada region of Maharashtra, dry seeding in June gives 30 per cent yield advantage of most kharif crops.