Introduction
Resource assessment
Resource management
Inter-institutional cooperation and networking
At a panel session on the final day of the conference, 14 participants formulated recommendations for future research on Vertisols in the areas of resource assessment, resource management and inter-institutional cooperation and networking.
The participants in this panel session were:
H. Eswaran
M.F. Purnell
J. Sehgal
S.M. Virmani
Desta Beyene
G. Haider
N. Ahmed
G. Lombin
O. Osman
R.D. Ghodake
P.L. Porter
Mesfin Abebe
G. Gryseels
M. Latham
Research on Vertisols, directed at developing new technologies for their enhanced agricultural exploitation, must be based on comprehensive analytical knowledge of these soils, including their geographical distribution, their agroclimatic properties and their agricultural potentials. Sub-Saharan Africa, with about 83 million ha of Vertisols (more than 25% of the world total) occurring under a wide range of agroecological conditions, can be considered an ideal field laboratory for such research.
Several specific gaps in the present information base have been identified.
The current system for classifying Vertisols does not take sufficient account of practical aspects of soil management and its variability as a function of agroclimate. Many clay soils which behave in much the same way as Vertisols in terms of their agricultural management are not classified as true Vertisols. Partly as a result of these shortcomings in the classification system, there are large differences in the estimates of Vertisol areas in individual countries, as well as in the African continent as a whole.
Detailed soil maps of Vertisol areas, produced from data gathered by aerial and ground surveys, are useful for resource allocation and planning purposes. However, full assessment of the agricultural potentials of Vertisols, and of the technological interventions necessary to realise these potentials, requires, in addition, detailed agroecological zoning of these soils, on the bases of average lengths of growing periods, and local and special climatic features influencing crop growth, such as rainfall distribution and dependability, frost, etc.
Vertisol surface characteristics vary considerably with agroclimate. More understanding is needed of the nature of this relationship, which can decisively influence the suitability of these soils for arable cropping.
Vertisols are, in general, regarded as marginal agricultural soils. Because their physical properties hinder conventional arable cropping, extensive areas are left under native range, supporting large numbers of domestic livestock and game. More data are needed on present land use systems.
Several specific research efforts are identified as being necessary to fill these gaps:
· A more flexible classification system for Vertisols needs to be devised, which also considers related clay soils and interactions between agroclimate and groups of clay soils in terms of their agricultural use.· Expansion of the information base on the geographical distribution and management-related properties of Vertisols can be undertaken by FAO and Unesco. IBSRAM's African Vertisol Network may support these activities.
· The preparation of detailed agroclimatological maps of Vertisol areas, which can be superimposed on the already available soils maps, will lead to comprehensive resource inventories at national and sub-national levels.
· More attention should be given to characterising the surface properties of Vertisols and their dependence on climate and management practices.
· Of particular interest for the design of improved Vertisol use options is the listing of all major production constraints encountered in the traditional farming systems on these soils.
· Aerial surveys should be used to gather detailed information for use in making accurate land-use analysis. National land-use planning departments are mandated to carry out this work.
In formulating proposals for Vertisol management research in sub-Saharan Africa, a systematic approach is needed which takes into account agroclimatology, socioeconomics, target farming systems and agrocultural policy considerations.
Soil water and nutrients
Soil moisture is the dynamic factor that largely determines the potential for arable farming on Vertisols. Very rapid changes from dry to wet and from wet to dry phases are likely to make Vertisols rather marginal arable soils in traditional farming, while slow changes may allow more extended cropping.
Improved Vertisol surface drainage in high rainfall areas affects not only soil moisture, but also soil surface temperature, nutrient mineralisation rates and therefore nutrient availability to crops. The acidity of Vertisols in these areas poses important fertility problems.
Rainfed agriculture on Vertisols in semi-arid and arid regions requires systematic interception of the scarce rainfall. The broadbed-and-furrow technology with tied furrows, constructed by using animal power, may represent a valuable alternative to conventional systems such as tied ridges.
Careful research on the complex interactions between soil water, plant nutrient availability and crop growth will lead to improved prediction of input efficiency on these soils.
· More detailed studies on Vertisol moisture dynamics are needed. The results are likely to have direct management implications (moisture conservation, crack reduction).· For cropping Vertisols in humid zones, there is a need for more research on more effective means of draining excessive water from fields without contributing to increased soil losses through erosion.
· Much experience on the use of Vertisols under irrigation is available in sub-Saharan Africa. Major research needs relate to the avoidance of salinisation with effective surface drainage, and to the avoidance of seepage water losses caused by cracking in field irrigation channels. Tillage/vegetative soil coverage practices affect soil water and irrigation water conservation, and need special attention.
· In the cropping of arid-zone Vertisols, under both rainfed and irrigated conditions, the most vital point to consider is the conservation of soil water through the use of appropriate tillage practices. Cropping systems must be devised in line with their most effective water use and in line with soil fertility maintenance requirements. Deep-rooted crops must be incorporated into the systems for maximum use of the moisture stored in the profile. Crops should also have adequate drought resistance to survive extended dry spell. Much attention should be given to building up organic matter in these Vertisols, which will contribute to better workability and soil water conservation.
Livestock
The most important contribution livestock can make to improved management of sub-Saharan Vertisols is their use as traction animals. Crop-livestock interactions in the predominant mixed and agropastoral farming systems can thereby be utilised and strengthened for the benefit of both sub-systems. Another contribution of livestock to the cropping part of the farming system is manure, which ought to be used more effectively as a source of domestic plant nutrient.
The application of draught animal power in improved Vertisol management for increased crop output will concurrently also increase the availability of crop residues for use as animal feed. Crop residues can quite easily be upgraded to productive animal diets with the use of suitable nitrogen supplements which should preferably be grown on-farm (legumes, particularly tree legumes). Increased crop grain output per unit area will also ease the pressure on arable land for exclusive grain production. This may allow some production of high quality animal feed on a portion of the land.
· Apart from work on draught animal technologies, livestock research on Vertisols with mixed farming patterns should focus on interactions with arable crop production. Socioeconomics, on-farm research and technology transfer
In the generation of Vertisol technology it is vital to have a clear understanding of the target farming community and its resource endowment, and to tailor research programmes. according to specific requirements.
Improved Vertisol management technology is never a single commodity technology; it normally implies quite considerable changes in farm resource allocation, cropping systems, soil fertility practices and animal husbandry. Transfer of such a complex technology tends to be a slower than single commodity transfer.
· Vertisol technology research needs to carry an economic dimension right from the start, to ensure that the economic implications of this technology can be adequately assessed, with clear indications of cost-benefit ratios, of the means necessary to guide the transfer and adoption of this technology in the target farming community, and of the actual impact of the technology. This economic dimension must therefore cover aspects of detailed economic analysis of the technologies proposed, of comprehensive baseline information of the resource including socioeconomic parameters, of risk studies, and of detailed economic monitoring of the technology performance on-farm. Market studies will reflect opportunities and bottlenecks in the target farming systems.· On-farm research on Vertisol technology needs a long-term perspective in view of the generally high variability in technology performance from year to year.
· In structuring Vertisol technology transfer, special attention should be given to the selection of representative test locations within the target areas on carefully identified benchmark Vertisols.
· Decisive efforts are required to simplify the technological message for the extension system, so as to lay down a foundation on which more advanced technological elements can later be built. This requirement calls for interdisciplinary research work, both on-station and on-farm, with research and extension institutions formally interlinked.
The transfer of Vertisol technology depends largely on the establishment of a formal inter-institutional agreement between research and extension agencies, with clear assignment of responsibilities in order to ensure effective feedback.
The considerable gaps in detailed knowledge, both of the Vertisols themselves and of the agroecology determining their most effective agricultural use in the sub-Saharan context, call for specific manpower training opportunities which range from formal training to in-service training of national staff working on such soils.
The African Vertisol Network coordinated by IBSRAM should be actively utilised by interested national research systems in sub-Saharan Africa:
· to increase the exchange of technical and management information,· to enhance specific training opportunities for scientific and technical staff working in Vertisol utilisation,
· to facilitate necessary funding for the implementation of Vertisol management research in member countries,
· to facilitate necessary counselling to national research programmes. and
· to offer and facilitate attractive publication opportunities for achievements of national programmes.
