Soil conservation is the prevention of soil loss from erosion or reduced fertility caused by over-usage, acidification, salinization or other chemical soil contamination. Soil conservation consists of all positive activities that man does to prevent soil loss (1). Soil conservation is the soil erosion antonym. Soil erosion is a natural process and, most of the time, it removes the top soil that contains necessary organic matter, nutrients, and micro-organisms that are required for plants to grow and thrive. Washed away soil, then, ends up in aquatic resources, bringing in pesticides and fertilizers used on agricultural lands. Healthy soil is important for plants to grow and flourish (2).
Severe soil loss in an area in Minab, Bandar Abbas Province, Iran.
Taking necessary steps to conserve soil is a part of the disciplines that keep various scientists and experts busy in investigating different aspects. There are several ways to conserve soil. Man can achieve it through appropriate agricultural practices, such as reversing the degradation of soil, water and biological resources, and enhancing crop and livestock production. Appropriate land use and management practices are essential components in achieving the food and livelihood security of a country (3).
Taking appropriate precautions to protect valuable soil
Symptoms of soil degradation are numerous and include the decline of soil fertility, the development of acidity, salinization, alkalization, the deterioration of the soil structure, accelerated wind and water erosion, and the loss of organic matter and biodiversity (4).
As a result of soil degradation, farm labour productivity decreases and revenues from agriculture fall, migration to urban areas will consequently increase, and rural poverty will be exacerbated. Efforts to restore the productivity of degraded soils must be coupled with other measures that affect the land use practices in a particular conservation agriculture, including good agricultural practices, irrigation management, and integrated plant nutrient management (5).
Wind Erosion and salinity has caused abandoned land
Why does this matter? Soil erosion is a slow, naturally occurring process that refers to the loss of a field’s top soil by water and wind or through the conversion of natural vegetation, such as forests and rangelands to agricultural land. While farming activities are carried out, the top soil is exposed and is often blown away by the wind or washed away by the rain (6, 7, 8). Since a great portion of human nutrients directly or indirectly come from appropriate soil management, conservation is crucial to the security and welfare of human beings.
The Extent of Erosion:
Other than regions well protected by vegetation covers, soil erosion happens almost everywhere, especially in the arid and semiarid regions of the world. Arid and semiarid zones cover approximately 40% of the land surface, with a continuous increase in the area by desertification processes, induced mainly by anthropogenic activities and/or climatic change. The process of desertification affects the world on ecological, economical and social levels. The lower rainfall in arid and semiarid areas, compared with that in humid climates, does not correspond to a lesser level of soil erosion by water. In fact, rainfall erosion can be higher in semiarid areas than in any other climatic zones (9).
Vegetation cover protects land from Erosion, Region Nizva, north of Semnan
Among one of the major variables affecting soil erosion, the rainfall pattern is important and complex. Since rainfall energy is one of the main active forces in the process of water erosion, it is extremely important to assess the response of the soil to different characteristics of precipitation. Knowledge of the rainfall characteristics allows for the safer planning of structures and agricultural practices aimed for soil conservation. The relationships between rainfall and runoff processes, which result in erosion at a given location, are generally complex. Prediction of runoff and soil loss is important for assessing soil erosion risks and for determining suitable land uses and soil conservation measures for a watershed. Soil erosion by water occurs as a result of the detachment of soil particles by raindrops and runoff. The most well-known and widely used parameter to predict the erosive potential of raindrop impact is the rainfall erosion index. It reflects the amount and rate of runoff generated by erosive storms. It is also known as the rainfall erosion power or R-Factor of the Universal Soil Loss Equation or USLE. This is partly because the rainfall of semiarid areas has a high proportion of convective thunderstorm rain with high intensity and high erosive power. It is also because there is poor protective vegetative cover, especially at the beginning of the rainy season (10).
In arid and semiarid areas, soils with little or no vegetation cover are exposed to torrential precipitation events, which are characterized by short durations and high intensities. They are prompted by the occurrence of physical and chemical processes that change the surface layer conditions, such as surface sealing and crust. When the surface is dry, a hard layer is formed (crust). Crusted soils are typical of these dry areas, where soil degradation is induced due to diminishing infiltration rates, as well as increasing runoff and erosion rates. Some of the soils common in semi-arid areas are particularly vulnerable, either because they have poor resistance to erosion (high erodibility), or because of their unsuitable chemical and physical properties (11). Gully erosion can be severe in semiarid climates as well, but the benefit/cost of gully control needs to be well considered in these areas (12, 13).
Soil Erosion due to wind and water Erosion, Zanjan pronvince, Iran
Soil Conservation and Water Conservation:
There are always strong links between measures for soil conservation and measures for water conservation, and this applies equally in semiarid areas (14). Experimental results have confirmed enhancement in soil productivity and conditions caused by soil and water conservation practices. Proper conservation techniques, such as engineering projects/practices, agricultural-technical measures, biological methods, and other comprehensive measures, will improve the soil’s physical properties and quality in long-term implementation. Results of field experiments show that the best management practices implemented in a series of areas not only significantly reduce soil loss in farmlands, but also improve soil characteristics, such as soil structure. Many measures are directed primarily to one or the other, but most contain an element of both. Reduction of surface run-off by structures or by changes in land management will also help to reduce land erosion. Similarly, reducing erosion will usually involve preventing splash erosion, the formation of crusts, or breakdown of soil structure, all of which will increase infiltration and so helps water conservation (15, 16).
Use of appropriate methods for soil and water conservation
Research increasingly suggests that the functional level of internal regulation in agro-ecosystems is largely dependent on the level of plant and animal biodiversity. Biodiversity in agro-ecosystems performs a variety of ecological services beyond the production of food. Those include recycling of nutrients, regulation of microclimate, local hydrological processes, suppression of undesirable organisms and the detoxification of noxious chemicals. Vegetation also significantly controls soil erosion rates. The decrease of water erosion rates with increasing vegetation cover is exponentially correlated. Various reviews reveal that the decrease in water erosion rates with increasing root mass is also exponentially correlated. The equation similarity of root effects with the equation for vegetation cover effects is striking, but due to incomparable units, it is yet impossible to determine which plant element has the highest impact in reducing soil losses. Moreover, all studies on vegetation cover effects only attribute soil loss reduction to the above-ground biomass. Whereas in reality, this reduction results from the combined effects of roots and canopy cover. Based on an analysis of available data, it can be concluded that for splash and inter-rill erosion, vegetation cover is the most important parameter, whereas for rill and ephemeral gully erosion, plant roots are at least as important as vegetation canopy. To comprehend the benefits and contributions of how vegetation influences soil erosion and slope stability, you may think of its role as either hydrological or mechanical in nature. The mechanical contributions arise from the physical interactions of either the foliage or the root system of the plant with the slope. The hydrological mechanisms are those processes of water use and movement in the slope.
Beginning of Gully erosion on an overgrazed land, Zanjan Province, Iran
The general roles that vegetation plays in slope maintenance and reinforcement are very encouraging. The net effect of vegetation is usually beneficial to slope stability. The protection of the slope against shallow seated land sliding is a key benefit of a revegetation or existing vegetation maintenance program. The function that mixed vegetation provides, it is increasing apparent cohesion of the surface soil structure and slope. The different types of root systems that plants provide can strengthen potential shallow seated failure planes on the slope by both fiber reinforcement of the near surface soil and binding soil structure together into a larger unit through tap or lateral root networks. Soil conservationists’ approach after the 1980s is moving away from using only mechanical works and structures in soil conservation programs (17). There is also increasing awareness of the ineffectiveness of terracing programs alone (18, 19).
Role of vegetation cover in recover of Badlands in Marzanabad, Chalous, Iran
Therefore, they are moving toward more integrated approaches of soil conservation (20). Also, the trend is moving towards the view that the only effective programs are those which have the full support of the local residents (21, 22). One must take into consideration that the subsistence farmer cannot afford to respond to philosophical or emotional appeals to care for the soil. This means in order for conservation measures to be effective, they must have visible short-term, as well as strategic benefits for the farmers and local residents (23). For the subsistence farmer, the benefit he would most appreciate might be increased yields per unit of land or perhaps better production per unit of labour or perhaps improved reliability of yield (24).
Subsistance farming in Taleqan Valley, Elburz Province, Iran
Soil conservation must be cost effective to be acceptable to farmers (25, 26). Then, the low production value of semiarid soils means that only reasonable designs are appropriate. On a fertile soil with good rainfall, it may be appropriate to invest lots of labour or money in sophisticated schemes for controlling run-off, but not in semiarid areas with low and unreliable yields (27). Attempts to eliminate soil erosion completely may be unrealistic, however, some level of erosion control must be acceptable. Also, some soil conservation measures failing must be compromised (28). A realistic approach in evaluating the failure in flood diversion systems or other soil conservation methods must be put in place. But the design and construction should be in a way that they could withstand the 30 year flood prediction. It would naturally increase the construction effort beyond what the farmers can provide. The same approach should be applied to all mechanical conservation programs in arid and semiarid regions too (29). In such cases, government’s ecosystems consultation and assistance is necessary. In this regard, farmers’ cooperatives and their experiences must additionally be investigated (30). It is extremely important that conservation techniques and structures fit the culture and social norms, as well as being well discussed with local people. Many conservation programs have failed because the technology was inappropriate, misapplied or because they did not take into account the social situation, and did not involve people.
Soil Conservation structure, Minab area, Bandar Abbas Province, Iran
Biological Soil Conservation; Conservation Tillage:
This sum of term includes no-till (31), reduced tillage, minimum tillage, direct drill, mulch tillage, stubble-mulch farming, strip tillage and plough-plant (32). The concept of conservation tillage is the main theme of the recommendations for croplands in countries with advanced soil conservation programs, particularly the USA and Australia (33). It has also been duplicated in other countries around the world. The application is mainly in highly mechanized farming with good rainfall for wind erosion control. It is less applicable to low input level crop production or subsistence agriculture.
Tillage farming, an appropriate farming technique for soil conservation
The principles are equally effective in any conditions, maximum cover by returning crop residues and not inverting the top soil and using a high density of vigorous crops (34). Conservation tillage also has been advantageous for reducing the need for terraces or other permanent structures (35, 36). However, there are several disadvantages that hinder the application of conservation tillage in semiarid conditions: dense plant covers may be incompatible with the well-tested strategy of using low plant populations to suit low moisture availability. Crop residues may be of value as feed for livestock. Planting through surface mulches is not easy for ox-drawn planters, although there may be no problem with hand jab planters (37).
The limited amount of moisture available to crop roots is one of the reasons for low yields in semiarid areas (38). The available moisture will increase if the rooting depth is increased (39, 40, 41). It has been shown that in some cases, deep tillage can be helpful. Deep tillage is beneficial for some crops, but not all and on some soils, but not all. Ripping or subsoiling can be beneficial as well. Either by increasing the soil porosity or breaking a pan that is reducing permeability. The deep placement of fertilizer can also be used to encourage more rooting at depth, but again, the application of this technique to subsistence farming will be difficult (42, 43).
An appropriate soil conservation technique on the slop
This title covers many different farming techniques similar to conservation tillage. It includes any farming practice that improves yield, reliability, decreases the inputs of labour, fertilizer and any other methods leading towards improved land husbandry, which is defined as the foundation of good soil conservation (44).
There is a long history of traditional farming and soil conservation practices, which have been tested and developed over a long period of time and it has included all the likely variations of climate. These traditional practices should give the best long-term result (45). One must bear in mind that the farmer’s interpretation of ‘best’ may be based on reliability rather than maximum yield (46). But arid and semiarid regions are rapidly changing and the traditional patterns may not seem relevant any longer. While tradition may incorporate the wisdom of centuries of practical experience, it may also be inappropriate where recent demographic pressures have already compelled changes. There is also the point that the agricultural scientist very often still lacks the recipe for certain success (47, 48). One cannot require farmers to adopt new practices that are only 50% successful. Possible new techniques should have the same basic characteristics as traditional practices. They should be easy to understand, simple to apply, have low inputs of labour and cash, must show a high success rate, and have a profitable return rate (49).
Terrace farming in a village near central desert, Yazd Province, Iran
An effective technique in soil conservation is the use of mulch, which does have a multi-functional effect on soil protection. So what is a mulch? It is a protective covering, usually of organic matter, such as leaves, straw, or peat, placed around plants to prevent the evaporation of moisture and the growth of weeds. Mulching reduces the deterioration of soil by way of preventing the runoff and soil loss, minimizes the weed infestation, and checks the water evaporation. Thus, it facilitates more retention of soil moisture and helps in the control of temperature fluctuations, improves physical, chemical and biological properties of soil, as it adds nutrients to the soil and ultimately enhances the growth and yield of crops. Furthermore, it has been reported that mulching boosts the yield by 50-60 per cent over no mulching under rain-fed situations (50). Successful use of mulching in semiarid regions are reported (51, 52). Trials of different materials and amounts are reported from India (53) and many other countries as well.
Mechanical Conservation Works:
There are no universal conservation practices that work everywhere. In other words, there is no one prescription for all. Soil conservation programs must be developed according region needs and public acceptance (54). Planning soil conservation is like having a large array of techniques and practices set out, each in a separate area. The objective of planning soil conservation is to make up a system by selecting a set of individual items, which are each relevant to the conditions, and that can be combined into a workable system (55).
An inappropriate soil conservation structure in Zanjan Province, Iran
The main factor in deciding which mechanical work to select must be to define the objective of a project, while looking at the large choice of techniques (56). In high rainfall regions, a common objective is to lead unavoidable surface run-off safely off the land using drains and ditches. In semiarid regions, the objective is more likely to slow down the run-off for infiltration or deposition of silt without diverting the run-off. This requires simple low-cost structures, quite different from the classical system of diversion drains, graded channel terraces, and disposal waterways. That is a high-technology layout of carefully designed structures. The approach may not be suitable for semiarid regions, where simpler techniques are required that can be laid out by village extension workers or the farmers themselves (57).
The question of benefits justifying the cost is appropriate when evaluating vast soil conservation projects in all developed countries. In the countries located in semiarid regions, this is complicated because alternatives are limited. A dispassionate scientific appraisal may say that some degraded land is best abandoned rather than trying to reclaim it with expensive soil conservation works, but if no better land is available for the production of needed food, then high-labour inputs may be acceptable as the only available option.
Any system of lines, banks, or bunds on the contour has important effects on cultivation of crops. These techniques alone can result in reduction of run-off and soil loss of at least 50% (58). Contour strip-cropping reduces soil erosion and protects water quality. Contour strip-cropping may also help reduce fertilizer costs by providing nutrient inputs naturally. Contour ploughing is an ancient soil conservation technology that is practiced in many countries around the world to mitigate the negative consequences of natural disasters on soil quality and composition. It is performed by following the natural contours when tilling the soil, planting and cultivating. It is best practiced on slopes between 15-20 degrees. It is a very cost effective and a sustainable practice when properly planned and applied (59).
Terrace farming as an ancient soil conservation technique
Terracing is a soil conservation practice applied to prevent rainfall runoff causing serious erosion on sloping land. Terraces consist of ridges and channels constructed across-the-slope. The major benefit, of course, is the conservation of soil and water. Terraces reduce both the amount and speed of water moving across the soil surface, which greatly reduces soil erosion. Terracing thus permits more intensive cropping than would otherwise be possible. Terrace cultivation or terrace farming is one of the oldest types of land and water resource management for large-scale farming. The main purpose of terracing land for farming is essentially to reduce the speed of water runoff and thereby reduce soil erosion by breaking the length of the slope that the runoff has available (60). There are two main types of terracing; graded and level.
Combination of ridge, furrow and bank farming
Terrace farming has been used for centuries. Historical records suggest that terraces have been in practice in Tanzania for about 300–500 years; in Peru, Guatemala, and Mexico for about 2,000 years; in Cyprus for approximately 3,000 years; in China for about 4,500 years; and in Yemen for the past 5,000– 6,000 years. Terrace farming has several merits. It is considered one of the oldest and most successful techniques for conserving soil and water during cultivation on steep slopes. Terracing of slopes conserves soil, regardless of the cultivation system used to produce field crops: in Parana (Brazil), it has been shown to reduce runoff and soil losses by half (61).
In semiarid regions, few types of terrace are likely to have widespread application. FAO recommends each use as follows: Level terraces may be appropriate where irrigation is available or intermittent level terraces used for run-off farming. Fanya juu terraces offer a way of achieving level terraces by limited input of labour over a period of time. Contour bunds may be useful because of the dual purpose of conserving both soil and water.
There may also be circumstances where a combination of shallow soils with limited storage capacity and heavy rain results in frequent surface run-off, which calls for a system of graded channel terraces, either without storage or with some storage and a designed overflow. The problem is that any such system is likely to be expensive in relation to the productivity of the land, and it is difficult to maintain grassed waterways as disposal channels when rainfall is limited and unreliable (62).
The discussion of terracing and conventional conservation works clearly points to the use of simple and easily applied measures. The first of these should always be farming on the contour. This alone can reduce soil loss to approximately half of what it would be with cultivation up and down the slope. We already know the fact that although rainfall in semiarid areas will be less in total, it can still add up to very damaging storms. So, it will usually be beneficial to have some form of structures in place which will slow down the surface run-off, encourages the deposition of suspended material, and reduces the volume of surface run-off to a minimum (63).
Some applications of stone lines have the primary objective of water harvesting rather than soil conservation. Run-off from un-cropped land higher up the slope runs down onto the cropland. It is spread by the permeable stone lines along with the run-off, which starts on the cropland. When this is the objective, there will not be a diversion drain at the upper edge of the cropland, and the stone lines should not use the reverse filter. Where the objective is to trap and hold sediment behind the stone bunds and reduce the slope by developing terraces, the reverse filter effect is desirable along the whole length of the bunds, if stones of different sizes are available.
This demonstrates the principle that it is always important to be quite clear about the desired objective (64). Even a simple device, like stone lines, can be built to help them to remain permeable or to silt up as quickly as possible or to silt up in the depressions.
Soil conservation is an important task, because soil is crucial for many aspects of human life, as it provides food, filters air and water, and helps to decompose biological waste into nutrients for plant life. Soil can be eroded away or become contaminated, which destroys its use. Soil conversation involves all works to ultimately eliminate or reduce contamination, degradation and depletion. Certain human activities can result in soil erosion, such as land clearance for farming or timber. These practices can also affect the quality of the soil and the ecosystem.
Soil erosion, including wind and water erosion, is considered as one of the most important elements of land degradation in Iran. Of the total land area in the country, approximately 75 million hectares (ha) are exposed to water erosion, 20 million ha to wind erosion, and the remaining five million to other types of chemical and physical degradation. As a result, over two million hectares in the country have been rendered infertile and equally large proportions of land surface have been afflicted by high levels of salinity (65).
Complete soil loss due to overgrazing and vegetation removal, Shiraz, Fars Province
Soil salinity is also a major limiting factor of agricultural development within Iran. Soil salinity is more severe in arid and semiarid areas, where an estimated 34 million hectares are affected by high levels of salt and of these 4.1 million ha of land are irrigated. About 50 percent of the irrigated areas depend directly or indirectly on groundwater, including spring water. The current annual rate of land loss due to water logging and salinity is about 0.5 million hectares per year. Increasing water shortages has led to digging of deeper wells resulting in water with higher levels of salinity. The annual economic losses due to salinization and land degradation have been estimated at more than USD 1 billion (65).
Soil loss due to wind erosion, Yazd Province, Iran
“Between two and four billion tons of soil wears away in Iran every year,” said Yousef Yousefi, director of the provincial office of Forests, Range and Watershed Management Organization in Markazi Province. If the numbers are correct, the rate of soil erosion in Iran is 20 times over and above the global average. “With an estimated price of $28 per ton, soil erosion costs Iran between $56 billion and $112 billion.” Iran earned $53.6 billion in oil exports in 2014 (66).
Water erosion due to wrong farming practice, Sedeh, Fars Province, Iran
Soil erosion in Iran is three times that of Asia and one of the highest figures on the globe. The fastest desertification of the century has taken place in Lake Urmia, where 480,000 hectares of the land have turned into desert within 15 years. The most important reason that we are moving towards an ecological disaster is due to policies we have adopted for the development of the country. They are not in accordance with our ecological conditions (67).
Surface erosion due to dry farming, overgrazing and vegetation removal, Taleqan, Iran
The above mentioned reviews of literature indicate the importance of protecting our ecosystems. Around the world, many scientists, researchers, experts and farmers are trying hard to improve the world’s knowledge of sustainability. However, Iran’s standing in this regard is at the bottom of the list. As we have mentioned earlier, Iranian regime’s open and secret gallows and extreme violation of human rights on a daily basis are certainly obvious to all, but its vicious intrusion on the natural resources and the country’s environmental violations are unfortunately not so obvious. The extreme damage has consequences and the lack of restoration to Iran’s ecosystems are going to impact the country for years and generations to come. They will pay a heavy price for the lack of knowledge, mistakes, disastrous ecological mismanagement and irresponsibility of a tyranny. What is happening now, in reality, it is an environmental genocide, which will victimize many future Iranian generations. They will work for years in order to reclaim a proper living environment. Lack of attention to the protection of environmental assets in Iran is clearly a violation of human rights and crimes against humanity. This act has not only targeted Iranians, but also will endanger regional and international peace and dignity. Thus, this act should strongly be condemned by all related UN and other international entities dealing with environmental issues in order to force the Iranian regime to act upon its national and global responsibilities regarding repairing Iran’s natural ecosystems.
Water erosion and generation of Gully around Bafq city, Yazd Province, Iran
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