OVERVIEW OF SORGHUM IN MADASCAR
The fourth world’s biggest island of Madagascar, situated off the coast of Southeast Africa, is well known for its many endemic plants and animals. Malagasy (people of Madagascar) are recognized as top rice eater in the world as well, 120kg/capita/year. Rice is the food staple of Malagasy, yet farmers still produce 80 percent of the country’s national rice requirement (http://www.irinnews.org). Additionally, in Madagascar, like many other developing countries in the world, population is increasing rapidly and agricultural lands remain stagnant or gradually shrink due to the urbanization and climate changes. Therefore, the rice demand will be far from being sufficient. In the southern regions of Madagascar, the problem gets even worse because of the harsh climate conditions that are not favorable for rice cultivation. It is needed to cultivate another crop such sorghum to substitute rice.
Sorghum is the world’s fourth major cereal in terms of production, and fifth in acreage following wheat, rice, maize and barley (www.fao.org), and is a staple food crop of millions of people in developing world. It can grow under wide range of climatic conditions. Its cultivation is extensive in marginal rainfall areas of the tropics and subtropics throughout the world. Some selected types are also grown in temperate regions. Therefore, this crop can perfectly grow in southern regions of Madagascar – semi-arid regions with an average temperature relatively stable (around 28°C throughout the year) and an annual rainfall below 400 mm. Most of the cultivars can grow in black soils capable of holding moisture. The soils show a great variability in their depth and characteristics – from shallow and bright to deep and black – in southern regions of Madagascar.
Since the last recent years, the Malagasy government launched some projects – among them CAPFIDA and PSDR (Projet de Soutien au Développement Rural) – to promote the cultivation of sorghum in the south-western and southern regions of Madagascar (Region Antsimo-andrefana and Region Androy). We carried out a survey on the evolution of cultivation of sorghum in those regions and its socio-economic effects on farmers.
MORPHOLOGY OF CULTIVATED CULTIVAR IN MADAGASCAR
This section will briefly describe the root, stem, and leaves of the most cultivated sorghum (“Apemby” in Madagascan) in regions of Antsimo-andrefana and Androy, the cultivar Kafir. Crown and brace roots constitute the primary roots of sorghum. Crown roots are formed at stem nodes located below or at the soil surface. The first four compressed nodes and the next two elongated nodes usually produce crown roots. Brace roots are formed at nodes above the soil surface, usually up to a maximum of three nodes above the sixth node. Nodal root appearance for sorghum begins at the 4 – 5 -leaf stage. The lateral roots that branched out from these primary roots of sorghum are termed secondary roots. Root distribution and activity can vary greatly depending on environmental conditions, mainly soil type, moisture, tillage, and fertilizer application.
The plant heights of typical sorghum vary from 1.5 to 2 m with 12 – 20 nodes and internodes. Leaves may be concentrated near the base or uniformly distributed and arranged alternating to the opposite side with parallel venation. Leaf consists of a sheath and a blade. The sheath is attached to the node and surrounds the internode. The leaf sheath is often covered with a waxy bloom. The angle of attachment of leaves to the stem varies. The leaf blade is long, narrow and pointed. The leaf blade may be straight or bend like an arc. Leaf margins of sorghum are toothed (finely serrated). 60 to 80 stomata per square millimeter of a leaf area are found in sorghum. These stomata can remain open over a wider range of leaf turgor enabling sorghum to maintain a higher rate of CO2 exchange at a high level of water stress.
Sorghum, like most grasses, has an incomplete but perfect flower, with both its male and female parts located at the head. It has a panicle inflorescence in which the floral units are on a peduncle located above the flag leaf. Because the stamen and pistil are located at same position, sorghum is considered self-pollinating, although it may show up to 50% cross-pollination depending on genotype. Nevertheless, breeding of sorghum is more difficult than other plants such as corn due to the natural separation of the two floral structures. The sorghum grain is a caryopsis. Grain is usually partially enclosed by glumes, which are removed during threshing. The shape of the seed is oval to round, about 6 mm diameter.
PRODUCTION OF SORGHUM IN MADAGASCAR AND ITS
Since 2008, according to Madagascar tribune, Malagasy government has aimed to produce 30000 tons of sorghum grain in 20000 ha area of southern regions of Madagascar with a yield of 1.5 to 2 t/ha. The government has implanted several storage rooms with capacity 5000 tons for sorghum as well. However, we estimated that only 1000 tons in 1000 ha surface area have been produced in 2012. These low production and yield were due to the lack of appropriate production technics and high yield cultivar, and the poor digestibility of locally produced sorghum grains.
Although rapid urbanization and increase in economic status has resulted in a decline in per capita consumption of sorghum in many countries, the consumption in southern regions of Madagascar has been increasing during the last recent years. Most of the production is consumed locally. Sorghum grain is mostly consumed directly for food (70%) as bread or cooked like rice. However, sorghum proteins become less digestible after cooking due to change in the structure of kafirin present in grain protein. It is also an important source of feed grain (25%). Sorghum has great potential as a fodder resource due to its quick and rapid growth, high green fodder yield, and good quality. Of late, sweet sorghum is emerging as an important biofuel crop, making sorghum a unique crop with multiple advantages as food, feed, fodder, and fiber. Hence, it is popularly known as a smart crop. In addition to these uses, sorghum crop residues and green plants provide building material, and energy for cooking. Industrial application of sorghum makes its cultivation economically viable for marginal farmers.The composition of sorghum grain is similar to that of maize or other cereal grains. However, the perceived poor nutritional and processing quality of sorghum is because of the presence of tannins and poor protein digestibility, which affects its use in food and feed. In contrast, sorghum is a good source of minerals and B vitamins such as thiamin, riboflavin, vitamin B6, biotin, and niacin, but refining leads to losses of all B vitamins. It has high potassium and phosphorus content, but its calcium content is low. Sorghum is a rich source of various phytochemicals such as tannins that are antinutritional values but have a significant impact on human health through high antioxidant activity against different free radicals.
CHALLENGES FOR PRODUCTION OF SORGHUM IN MADAGASCAR
Madagascar is away far from reaching it goal in term of sorghum production. Sorghum is still cultivated by poor farmers and grown under subsistence conditions. Hence, they cannot take advantage of high yield potential, as the growers are unable to follow improved management practices. Higher yields can be obtained by growing varieties/ hybrids with improved tolerance to drought, heat, and low soil fertility, as well as resistance to pests and diseases. Pest problems comprise one of the major constraints for achieving higher yields in sorghum grown in tropical areas. Immense losses are caused by insect pests attacking sorghum at all stages of growth, the important ones being shoot fly and aphids in winter sorghum. The midge and ear-head bugs attack at the grain-filling stage leading to the losses up to 100%. The grain can be used for industrial purposes, such as potable alcohol, malt, beer, liquids, gruels, starch, adhesives, core binders for metal casting, ore refining, and grits as packaging material, yet this is not the case for Madagacar.