7.1 Faulty irrigation schemes
7.2 Extensive vs. intensive irrigation
7.3 Deforestation
7.4 Water pricing
7.5 Size of holding and land consolidation
7.6 Land tenure system
7.7 Role of appropriate technology
7.8 Extension and farmers’ education programmes
Socio-economic and even political considerations often become extremely important in accentuating the problems of land degradation through salinization, sodication and related processes. Such factors are often beyond the control of individual farmers and for this reason appropriate policy decisions and corrective measures become the responsibility of respective governments. Some of the more important factors are discussed below.
The introduction of irrigation is often considered a solution to the pressing problems of the arid and semi-arid regions. However, there are numerous examples of soils degraded and lost to production due to ill conceived or poorly implemented irrigation schemes. The most serious problems in irrigation development do not relate to the storage and delivery of water but to the secondary effects of irrigation.
According to an FAO study there has been a galloping inflation in the cost of land and water resources development. Thus the development cost of surface irrigation, including storage dams, drainage and on-farm works per hectare increased from US $500 to 2000 in 1970/71 to more than US $10 000 in 1980. This figure is likely to increase further in the future as the easier and simpler projects are completed leaving the increasingly difficult projects. Because of the high costs involved to make the irrigation projects operational, there is a tendency to find only the money required for the rapid establishment of irrigation facilities in order to grow marketable crops quickly and to defer or omit drainage works in the hope that either they will not be required or that the necessary funds will be found when the project is producing a profit. Unfortunately, the cost of providing drainage and reclamation when the problems of waterlogging and salinity have already appeared are much more, apart from the huge losses already incurred through partial or complete loss of production of many areas. For any lasting success, all irrigation projects need sound drainage networks considering soil, climatic, geohydrological and geochemical factors as also the social and economic setting of the region. If the drainage networks are put into operation at the same time as the water supply from canals, a great saving will ultimately result to the project.
In practice, the time gap between the start and completion of a major irrigation project may normally extend to over 10 to 15 years. Often the increased costs during this period result in spending the entire project money on the construction of storage works, main and secondary canals, leaving little or no money for investment in ‘on-farm irrigation development’. As a result, a sizable portion of the water delivered to the farms is wasted due to irregular distribution within the farm, deep percolation losses below the root zone and surface evaporation during application (Plate 13). This results in the development of a high water table and salinity problems much sooner than anticipated. This calls for appropriate allocation of money within the project funds for ‘on-farm water management’ including lining of field channels and water courses to prevent seepage losses, proper land shaping, field layouts for uniform water application, etc.
Water resources being limited, a choice has always to be made whether to bring a relatively small area under intensive irrigation, i.e. to grow two or more crops in a year or to adopt a protective type of irrigation on a large area. In theory, concentrated watering, considering the water requirements in an intensive cropping agriculture along with provision of adequate drainage, will be more conducive to the control of salts in the root zone. In practice however, when irrigation projects are planned there is a tendency to bring more area under irrigation than the available water resources would permit under an intensive agriculture. This is done for political and largely social reasons. For example, in India although it has been realized that concentrated efforts to irrigate areas with the most favourable climate and soil and topographical conditions would cost less and would give substantial increases in production, it would at the same time amount to postponing irrigation indefinitely in areas where the agricultural population is living on subsistence agriculture with the perpetual hazards of drought and other vagaries of nature. For this reason the government has adopted a judicious combination of extensive and intensive irrigation since the national policy is to reduce the economic gap between one section of the people and another, and also to minimize regional imbalances. Spreading water over a wide area often leads to speeding up the rate of salinization without eliminating the rising groundwater table. This is so because insufficient water is available to meet both the crop water requirements and the leaching requirements for the control of salts in the root zone.
Human interferences resulting in indiscriminate and large-scale deforestation in recent years has been an important factor that has resulted in altering the water balance of large areas, in many cases resulting in serious salinization problems both in the irrigated and unirrigated areas. Unfortunately this fact has not been taken seriously and this is the reason for lack of systematic studies to evaluate the magnitude of the problem in many developing countries. Australian work has shown that reduced evapotranspiration, which is common when the native forests are converted to agriculture involving non-irrigated annual crops, may result in a build-up of the water table. In one study it was estimated that the increased recharge to groundwater due to a change from native woodland and forest to dry farming ranged from 23 to 430 mm per year (Peck, 1975). Such an alteration in the groundwater balance disturbs the distribution of salts and has resulted in widespread salinization problems in many parts of the world. The solutions to the problem appear complex but most include rational land use aimed at partly restoring the original hydrologic balance together with site treatments which must be chosen in accordance with local conditions.
Existing water laws and water pricing systems are yet another factor determining the efficiency of on-farm water use. In most developing countries irrigation is supplied free of charge, although in some taxes are levied to mobilize resources for financing irrigation works. The farmers who operate their own pumps or buy water from pumps owned by others must pay for the amount of water they use. The water use efficiency of such farmers is therefore much higher than that of those who do not pay for water. The latter case has resulted in farmers using quantities of water in excess of that required to meet the crop consumptive use causing the problems of waterlogging and salinization. Although it might entail many difficulties, a change in the policy to charging for the water used will help increase over-all water use efficiencies and control salinity.
In many countries the land holdings are small and spread over a wide area. As a result, the attention of service agencies is diffused and much time and effort has to be concentrated on encouraging proper management of inputs by farmers. Land fragmentation and associated differences in cropping and management help the spread of secondary salinization. Differences in cropping patterns and irrigation regimes between adjacent farmers will cause migration of salts from high to low spots, from crop areas with more frequent irrigations to those with less frequent and from relatively wet soils to relatively dry soils. Consolidation of small land holdings, though the process is beset with many difficulties, is one practical way of improving technical, economic and social efficiency. Figure 41 presents the layout of a 120 ha pilot project area before and after land consolidation (Sinha and Borah, 1980). Out of 120 ha, only 97 ha were consolidated, the remaining 23 ha being left unconsolidated for comparison. The average size of the holdings in the project area before development was 0.35 ha, the sizes varying from 0.05 ha (minimum) to 3 ha (maximum); the individual plots were scattered and were still smaller, to the extent of 0.01 ha. The consolidation of land on a scientific basis was found essential for ease of water management and other agricultural operations. Therefore, after the acquisition of the land, it was micro-levelled to locate natural ridges and valleys along which the field channels and water course could be aligned. When the construction of channels and drains was over, plots were divided according to the holdings of the farmers in such a way that each plot had a direct access to the water course, the drain and farm land. Table 46 shows a very significant and interesting comparison which proves the usefulness of the consolidation of holdings.
Figure 41 Layout of a 120 ha pilot project area before land consolidation
Figure 41 Layout of a 120 ha pilot project area after land consolidation
Table 46 COMPARATIVE FIGURES OF ON-FARM DEVELOPMENT WORK WITH AND WITHOUT CONSOLIDATION OF LAND HOLDINGS (Sinha and Borah, 1980)
|
Item |
Without Consolidation |
With Consolidation |
|
Length of irrigation channel (m/ha) |
140 |
85 |
|
Length of drains (m/ha) |
153 |
140 |
|
Length of roads (m/ha) |
37 |
60 |
|
Distance of remotest plot from the irrigation channel
(m) |
50.8 |
Negligible |
|
Distance of remotest plot from the field drain (m) |
50.6 |
Negligible |
|
Area occupied by the channels and drains (% of the field
area) |
4.7 |
3.8 |
|
Area occupied by roads (% of the field area) |
1.00 |
1.55 |
|
Length of field bunds (m/ha) |
1 000 |
375 |
The land tenure system can also play an important role in the spread of salinity. Many cultivators in developing countries, such as India and Pakistan, are share-tenants who are often moved around by the landlords to different plots each year. As a result the cultivators nave little interest in protecting the soil from degradation due to salinity or-other factors. On the other hand, long-term tenancy or private ownership of land will offer incentives for conservation measures including control of salanization.
7.7.1 Testing the technologies
Extreme pressure on land resources and the ever-growing need to produce more food for the increasing population require that the salt-affected soils be restored to productivity and effective steps taken to prevent desertification of new areas being brought under irrigation at huge cost. To accomplish this, it is necessary to develop appropriate technologies suited to a particular region or country. By the term ‘technology’ is meant the whole range of management practices that go into farm production in such areas. This includes the method of land preparation, best suited crops, varieties and cropping sequences, their fertilization and best suited cultural practices including planting techniques, best suited irrigation, drainage and on-farm water management practices, need of amendments, etc. And the term ‘appropriate’ implies that the technologies are relevant and adaptable down to the farmers’ level. In the context of developing countries the technologies developed, in general, must:
- be relevant to the development of the majorityTo illustrate this, although the basic principles involved in the reclamation and management of salt-affected soils are now well understood, the adoption of advanced technologies in an economically less advanced country may be difficult without overall economic development and an improvement in the level of education of the people. Thus, what might be possible for a farmer in the arid parts of California, USA, or in Australia by way of water management might be completely out of reach of the cultivators in arid Rajasthan in India. For example, in theory, while it is now well established that greater efficiency of water use and salt leaching can be accomplished by the adoption of sprinkler irrigation, for economic reasons it might be impossible to adopt this method over wide areas in most developing countries. And even if the economics permitted it, the adoption by illiterate farmers of such sophisticated water control equipment will present difficulties when it comes to maintenance, etc. As an example of the latter, in the past decade or so, millions of dollars have been invested in providing modern subsurface drainage systems in Iraq with the aim of restoring productivity to the land that has gone out of cultivation due to salinization. Iraqi farmers have had little or no experience with such drainage methods and are generally ignorant of them. A well designed and operated drainage system can greatly increase the productivity of irrigated agriculture but only if it is effective down to the farmer’s fields. The individual farmer must understand the importance of drainage. His full cooperation is necessary to maintain the field ditches and interception drains to ensure the functioning of the costly drainage system. Thus, in order to achieve the desired objectives of increased food production from these areas, it will be absolutely necessary to elevate the overall level of education of the farmers (Allahwardi, 1979).
- be based on low levels of investment
- be ecologically sound
- be based primarily on local resources and skills
- have high employment potential
- be in harmony with rural traditional cultures, and
- be able to contribute to the self-reliance of the rural economy.
It is apparent, therefore, that if technology for the reclamation of salt-affected soils and for the prevention of the spread of salinity is to be effective and lead to continuous improvement in food production, it is essential that:
- relevant farming technologies for such areas be developed to meet realistic goals considering the social, economic and political setting on the one hand, and tradition and level of education of the farmers on the other;New or existing technology must be tailored to meet local conditions and this can best be accomplished by teams of scientists who are well aware of the constraints operative at the farmers’ level. In other words, relevant research conducted by scientists who appreciate the social, cultural and political aspects of the country and who can guide team efforts towards the best solutions under the realities with which the farmers work. Research programmes of the necessary magnitude must be organized so as to provide continuous support to the field programmes aimed at improving the existing methodologies of reclamation and on-farm water management practices.- there is a continuous effort to improve upon the technologies as more scientific knowledge and experience is gained and as the economic conditions become more favourable.
Scientific technology for the reclamation and management of salt-affected soils and for improved on-farm management practices must be tested on a pilot project scale before being transferred on a large scale to the farmers’ fields. The objectives of such a pilot project should include;
- testing and demonstration of the new or existing technologies on the farmers’ fields;Only well tested technology with proven benefits should be passed on to the farmers. Pilot projects also serve to define the infrastructural needs and the various likely impediments in the transfer of technology. For example, while land shaping and levelling are the important components of any project aimed at improving the on-farm water management, many farmers do not have adequate resources and do not own the required implements and machinery required for this. Experience gained in the pilot project must define a strategy to accomplish this. Reclamation of sodic soils requires application of amendments. How can availability of the amendments to the farmers be ensured at appropriate cost? Should there be an element of subsidy? If yes, are institutional finances available or can they be mobilized?- modification of the technologies to suit the local conditions, if required;
- critical calculation of the profitability and economics of the new technologies;
- identification of bottlenecks in the transfer of technology whether they are of a technological, socio-economic or administrative nature.
Often the solution to a salinity problem may lie outside the capability of a single farmer or even a group of farmers. Such is the case where natural drainage channels do not exist to allow the salt-laden drainage waters to be disposed of. Under such circumstances a central drainage facility or an evaporation pond area may have to be developed if the salinity problems of the area are to be solved. Sometimes it is helpful to use pumped groundwater for irrigation, particularly when the groundwater has low total salinity. This provides not only a source of irrigation but also acts as an effective drainage measure (Narayana et al. 1977; You and Wang, 1983). If the farmers are advised to install the wells, do they have the resources; what are the alternatives? If particular crops or crop varieties are recommended for adoption in an area, how can the availability of good seeds to the farmers be ensured? If it is intended to introduce or recommend new crops to be grown in an area for reasons of greater tolerance to salinity or sodicity conditions, are there adequate marketing facilities for the produce? Workable answers to these and several other questions that arise at the testing stage must be arrived at so that when large-scale programmes are taken up, they are effective.
Irrigation farming calls for particular skills in the application of water and the tillage of irrigated soil if its great potential for increased productivity is to be developed and sustained. The efficiency of irrigation schemes rests, in the final analysis, on the individual cultivator who is the most important link in the chain of production. When irrigation is introduced in a new area the farmers of the region have had little or no experience in handling large quantities of water on the farm. Since the cultivator may be tradition bound and lack the benefit of education, effort and ingenuity must be applied to convert him into an efficient irrigator. To ensure steady progress in irrigation methods and water use efficiency the farmer must be kept informed of new ideas through organization of appropriate training and other extension programmes. Well designed and operated irrigation and drainage systems can increase the productivity of irrigated agriculture but only if they are effective right down to the farmer’s field. The individual farmer must understand the importance of land shaping and uniform water application, the need and desirability of irrigating crops based on available scientific information, the importance and best ways of maintenance of field, channels including proper lining procedures, best methods for control of weeds in irrigation and drainage channels, etc. A continuous effort to elevate the level of education of the cultivator will result in enhanced capability to manage the land and water resources with minimum degradation through salinization and related phenomena.
