The single most important technological change in sorghum cultivation since the 1960s has been the development and use of hybrid seed. Hybrids are now used widely in large parts of the world. Almost the entire sorghum area in Group II countries, and large portions in Group I (except in Africa) are occupied by hybrids. As a result, productivity and uniformity in maturity and grain quality have increased. This has also encouraged mechanization and increased the use of fertilizers and other purchased inputs. In India, where about 55 percent of the sorghum area is sown to hybrids, yields have approximately doubled in the 30 years since hybrids were first introduced.
Issues relating to sustainability and the environment are becoming increasingly important. As a result of population pressures in most Group I countries, particularly in Africa, fallow periods are being shortened and more marginal land being brought under cultivation. These marginal lands are farmed with little or no fertilizer, leading to soil degradation. In addition, climate change (lower rainfall, higher temperatures) and periodic drought are making cultivation riskier, forcing farmers in parts of Africa to adopt inappropriate production practices. The net result is falling production and productivity, and production practices that are unsustainable in the long term.
Another important environment-related issue is infestation by Striga, a parasitic weed, several species of which occur in Asia and Africa. Infestation of continuously cultivated fields has become a major constraint to sorghum production in many parts of Africa. The area affected and infestation levels have increased, exacerbated by the drought years of the 1970s and deteriorating soil fertility. Heavy infestation can leave the land unfit for cropping and fields have been abandoned in the worst affected areas. Striga currently affects an estimated 8 million hectares in Africa - almost 40 percent of the total sorghum area - and annual yield losses are estimated to be worth over US$ 90 million. The effects are likely to be long lasting as Striga plants produce many millions of seeds that can lie dormant in the soil for up to 15-20 years6. Striga control (using a combination of genetic and management options) is an important research focus, but has so far not been successful. Although several control options have been developed, most are either too expensive or otherwise impractical for smallholder farmers to adopt.
[6. Striga also attacks other cereal crops, such as maize and pearl millet, and some legumes, such as cowpea.]
In countries where hybrids are cultivated, there are breeding programmes in place to produce new parent lines and test new grain and forage hybrid combinations. The private sector is a significant contributor to this effort. In many other countries (mainly in Group I), public sector breeding programmes for open-pollinated varieties have been initiated. Historically, selection was largely for high grain yield, but breeders are now focusing on combining grain yield with grain quality, disease and insect resistance and stover yield. A number of improved varieties have been developed, but dissemination has been poor, especially in Africa, because of inadequacies in seed production and extension support.
Crop management research is conducted in both Group I and Group II. Although the need for such research is most crucial in subsistence farming systems, more attention is directed toward semi-commercial mono-crop systems. A considerable amount of research has been carried out on the individual components of cropping systems or on specific aspects such as fertility management or pest control. Virtually all activities are undertaken by the public sector. However, greater effort is needed on crop-livestock interactions and longer-term sustainability problems. Adaptive research needs to focus on a wider range of solutions that fit the cash constraints and risk perceptions of smallholder farmers.
In most Group I countries, particularly in Africa, breeding and resource management research alone are unlikely to result in major improvements in sorghum production. Technical solutions are available for many existing problems, but improvements in market infrastructure will be required to support more intensified production and break the downward spiral of yields and soil fertility.
It is particularly important to develop the seed market in order to provide farmers consistent access to new varieties and to strengthen input markets to ensure that agrochemicals become cheaper and more easily available. In some countries stabilization of prices is also important, in order to encourage greater investment in sorghum production.