Sorghum
RWA 
ENG1. Introduction
Sorghum is the fifth most important cereal crop in the world after wheat, rice, corn and barley. It is an environmentally-friendly crop as it is water efficiency, requires little or no fertilisers or no pesticides and is biodegradable. In Rwanda, Sorghum is an important cereal grown in high altitude, middle altitude and low altitude agroecological zones. It is consumed locally as porridge, a famous breakfast for many Rwandan people and is brewed as alcohol and non alcohol local beers, which are important drinks in Rwandan culture, ddespite its importance, sorghum yield is low at farm level. The major production constraints are Striga species weeds, lack of high yielding varieties, low soil fertility, pests and diseases, low farmers’ knowledge on appropriate cultural sorghum practices.
2.Varieties
There are more than 200 sorghum varieties in Rwanda and many of them are landraces that are conserved in Rwanda National Genebank. In terms of high yielding varieties, Rwanda Agriculture Board (RAB) promotes 6 varieties which are suitable to different agro-ecological zones:
– For low altitude agroecological zone: IS21219 and IS8193 are high yielding varieties compared to the remaining ones.
– For Middle altitude agroecological zone: Kigufi, Ikinyaruka and the same variety IS21219 and IS8193 are doing well in this agroecological zone. Figure 2 shows respectively IS21219 and Kigufi varieties grown in Rubona Center for seeds multiplication.
High altitude agroecological zone: there are 3 varieties BM1, BM 33 and N9 that are giving high yield compared to the other varieties. The figure below shows N9 variety grown in Rwerere Center field in 2009.
1.1. Field preparation
Sorghum crop has to be sown in rows spaced with 0.75 m and 0.20 m within row. It can be sown continuously or in holes. Figure 4 presents rows tracing and sorghum sowing respectively
Before planting sorghum, field has to be prepared very well. Soil has to be ploughed twice in order to have a good seedbed before sowing.
1.2. Fertilization
Sorghum crop has to be fertilized with organic manure and mineral fertilizers. A total of 200 kgs per 100 m2 (per Are) of well decomposed organic manure has to be applied before carrying out the second land preparation. Also 2.5 kg/Are of NPK 17-17-17 has to be applied during sowing or 2 weeks after emergence.
1.3. Rows tracing and sowing
Sorghum crop has to be sown in rows spaced with 0.75 m and 0.20 m within row. It can be sown continuously or in holes. Figure 4 presents rows tracing and sorghum sowing respectively
1.1. Weeding
Sorghum crop has to be weeded as deemed necessary but at least it has to be carried out twice, 1 month after seedlings came out and before earthing up. Figure 5 shows weeded sorghum seedlings
1.2. Fertilization
In addition to applied manure and fertilisrs before sowing, 1kg of Urea per Are has to be applied during earthing up cultural practice.
1.3. Thinning
When the sorghum crop is sown continuously, weak plants have to be removed and remain with vigorous plants at the same spacing of 0.20 m between plants. Thinning has to be carried out for the first time when sorghum plants have like 0.10 m length and for the second time when they have around 0.20m length.
1.3. Earthing up
Earthing up has to be carried out between 1 month and 2 months related to maturity period of the concerned variety. The following figure show the sorghum crop after earthing up.
1.1. Striga sp
Striga is a root parasitic weed which is a major constraint to sorghum production, particularly in semi-arid regions of sub-Saharan Africa, where it can cause up to 100% yield loss in farmers’ fields.. Striga ssp attack its host by attaching its roots in sorghum roots and therefore Striga cause damage to sorghum in two ways. The first negative effect on sorghum growth is the competition for water and nutrients while the second one is the disruption of the sorghum hormonal balance. The control of Striga is very difficult because the parasite causes damage to sorghum before emerging above the ground. Despite this, many control options against Striga have been studied ranging from cultural and mechanical control methods such as hand weeding, crop rotation, nitrogen fertilizer and Striga resistance/tolerant varieties. The figure below shows sorghum crops damaged by Striga hermonthica and striga asiatica respectively .
1.2. Sorghum shoot fly
Sorghum shoot fly is caused by Atherigona soccata and is one of the most damaging insect pests of sorghum. To damage sorghum plants, larvae cut the growing point, and the central leaf dies, resulting in the typical dead heart symptoms. The dead leaf can be pulled from the plant and, at the base, emits an odor. The young, whitish-yellow maggot feeds on decaying plant tissue. Most damage occurs one week to one month after plant emergence. Effective control practices are early planting; high seeding rate and use of shoot fly resistant sorghum varieties.
1.3. Sorghum stem borer
Sorghum stem borer is caused by Busseola fusca. It is a key insect of sorghum. As symptoms and damage, young larvae eat leaves and mature larvae bore into stalks and produce dead hearts. Large larvae tunnel in stalks causing reduced grain fill and increased stalk lodging. Stalk borer damage also may make plants more susceptible to stalk rot diseases. Boring by larvae often causes the peduncle to break and panicle to fall. To control this insect, it is advised to destroy or to burn dry stalks and the use of resistant varieties.
1.4. Sorghum ergot
Sorghum ergot is caused by a fungus called Claviceps africanae. The disease symptoms begin after flowering and the fungus infects unfertilized flowers and as a result, it produces sugary exudates on the infected flowers. After maturity, the infected seed produces an elongated black horn resembling ergot of rye but which are much larger. Control of the disease is possible by rotation and by planting resistant cultivars.
1.5. Sorghum midge
Sorghum midge is caused by Contarinia sorghicola. It is the most widely distributed of all sorghum insect pests and it occurs in almost all regions of the world where sorghum is grown. As symptoms, eggs are laid inside the glumes of the flower; and larvae feed on the development seeds, producing empty spikelets that give the appearance of failure to set seeds. Early and uniform planting of sorghum is the most effective cultural management method. Also cultural practices that promote uniform panicle exertion and flowering in a field are important in midge control. A deep plowing sorghum residue kills some overwintering larvae, reducing sorghum midge abundance next year. Resistant varieties can be also very effective.
1.6. Sorghum grain weevil
Weevils are the primary and most destructive insect pests worldwide of stored sorghum grain, especially in warm, humid countries. Weevils infest grain in the field and in storage. The adult weevil bores a hole into a sorghum grain, deposits an egg, and covers it with a gelatinous substance. As methods of management, stored grain insect pests can be managed by sanitation, well constructed and maintained bins, and residual insecticides like Skana Super has to be applied to the bin and grains.
Harvesting
Sorghum has to be harvested once the grain has reached the physiological maturity and when is no longer accumulating dry matter within the grain. Grain sorghum matures from the top of the head and progresses downward to the base and it is important to check the bottom of the panicle to determine whether the grain is mature or not.
Sorghum grains (seeds) have to be protected against weevils and it has to be dried in a well cleaned area to avoid contamination of other materials as well as pests and diseases. Aeration is also an important management tool for maintaining grain quality in sorghum storage as it extends the storage life of grain by removing odors, preventing moisture accumulation and controlling conditions conducive to mold growth and insect activity.
When the sorghum grains are well dried, they are threshed, winnowed and stored in clean, dry and aerated place.
Sorghum is used for various products ranging from porridge, paste (umutsima), cooked grains ( impengeri), sorghum beer and other sorghum flour based products: biscuits, cakes, bread.