Influence of Nutrient Rich Organic Wastes in Wastelands Reclamation

Influence of Nutrient Rich Organic Wastes in Wastelands Reclamation

EXECUTIVE SUMMERY

Exploration for natural resources and their utilization are present ever since the existence of human civilization. In India, land and water resources are the two important ones which determine our development. We possess large geographical area of 329 M.ha and unfortunately, nearly half of it is characterized with low soil fertility. Thus, nutrient limitation is an issue of concern in these marginal lands and several initiatives have been made in the past on their improvement. In contrast, we are also seeing nutrient surplus situations, sometimes even toxicities, in urban areas due to domestic and industrial waste disposals. Chemically, these wastes are organic in nature and rich in plant nutrients. An attempt was made to match these contrasting situations i.e. application of nutrient rich organic wastes to meet the nutrient requirements of tree species planted on less fertile wastelands. Thus, the objectives of the experiment were,

- To characterize the wastelands in terms of physical and chemical features as soil
limiting factors in afforestation programme
- To characterize domestic and agro-industrial organic wastes for suitability as
nutrient source in afforestation programme
- To evaluate the changes in physical and chemical properties of wasteland soils
due to organic wastes application
- To evaluate the growth performance of tree species due to organic wastes
application in wastelands

To meet these objectives, a preliminary survey was carried out initially in the Eastern Dry Zone of Karnataka to characterize the wastelands and also to choose a suitable site for the field experiment. The soil samples collected were analyzed at the Dept. of Soil Science, UAS, Bangalore and KSCST, IISc, Bangalore. A wasteland belonging to ‘Sri Adichunchanagiri Blind School’ - A charity, near Ramanagaram, Bangalore Rural district was chosen to carry out the nursery and field experiment.

Organic wastes from sugar mill, paper mill, distillery plant and municipal sewage treatment plant were chosen along with Farm Yard Manure (FYM) as control. The organic wastes were applied at 1:1:1 and 1:1:2 (soil:sand:wastes) ratios in field experiment. Tree species namely Pterocarpus marsupium, Melia dubia, Azadirachta indica, Pongamia pinnata, Tectona grandis and Holoptelea integrifolia were chosen for field experiment.

Features of wasteland: Wastelands were physically degraded having scanty vegetation. The topography varied from gentle slope to highly undulating, leaving a severely eroded land at the surface. The soils were gravelly in nature and low in nutrients content compared to that of normal soils. The gravel occupied almost 20-30 per cent of the soil bulk volume and thus, the nutrient and water availability is much less than we generally presume.

Nutrient value of organic wastes: The nutrient contents varied among organic wastes and their concentrations depend on the associated treatment processes. Organic carbon content ranged from 20-46 per cent and nutrient contents were N - 0.37 to 1.69 %, P - 0.17 to 1.64 % and K - 0.10 to 0.73 %. Phosphorus content was substantially high in sugar industry waste while, phosphorus, potassium, sulphur and calcium contents were higher in distillery sludge. Heavy metal contamination was recorded only in municipal and paper industry wastes.

Field experiment: Both type of organic wastes and their levels influenced the plant growth. It was of the order Distillery > Municipal > Sugar > FYM = Paper wastes. Application of wastes at 2% recorded higher growth compared to 1% of wastes application to soil. The plant height recorded at the end of the experiment was in the order Melia dubia > Azadirachta indica > Pongamia pinnata > Holoptelea integrifolia > Pterocarpus marsupium while, the growth rate observed was in the order: Pterocarpus marsupium > Melia dubia > Azadirachta indica > Pongamia pinnata > Holoptelea integrifolia. Soil nutrient status was very much influenced by the sludge type, their levels and seasons. The observations made in this were very similar to that of nursery experiments. Municipal wastes treatment recorded slightly higher levels of micronutrients and heavy metals. Heavy metals (Pb, Cr, Ni) were recorded even in paper wastes applications.

I. INTRODUCTION

The modern world has realized now that the over exploitation of natural resources in the past has resulted in resource degradation and environmental problems. Thus, both utilization and conservation of natural resources are the two important aspects of resource management to achieve sustainable national development. Land and water are the two important resources, which need to be conserved for future generation both quantitatively and qualitatively. Though we possess large geographical area of 329 M ha nearly half of it is less productive. Poor soil fertility, problems of drainage, salinity and alkalinity, erosion etc have rendered them under productive. With the existing situations, we have to meet the demands of the present human (18 % of the world) and livestock (15 % of the world) population. Thus, the pressure on land and water is extremely high and needs to be managed effectively.

On the other hand, congregation of population coupled with industrial boom in urban centers is posing different kind of problems. The wastes are being generated in enormous quantity both from domestic and industrial units. Disposal of these wastes is a serious problem as they are bulky in nature and at times they may be contaminated with toxic compounds. The present methodologies of disposal are posing serious environmental problems and also on human health. Some of the areas are becoming misfit for human settlements. As the above process is part of national development, it becomes imminent for the researchers to look for safe management of resources under existing conditions.

Critical analyses of the above issues clearly indicate two contrasting situations – large tracts of nutrient depleted wastelands on one side and nutrient rich organic wastes on the other side. Though, both the contrasting situations are resulting in resource degradation and some of the wastes generated from urban and industrial units could become alternate inputs. The wastes from municipalities (sewage sludge) and distilleries, sugar mills, paper mills, coffee pulping and fruit processing units e tc., are having considerable amounts of organic matter and nutrients and may be effectively used as a nutrient source in wasteland reclamation. However, presence of heavy metals in some of the wastes may become a constraint. Such problems may be anticipated in domestic wastes due to illegal discharge of untreated effluents by a few industries. In case of agro-industries, such contaminations are less expected as heavy metals are not used in any of the processes and thus, they can be explored for their nutrient value. By keeping these in view, the research proposal was made with the following rationale.

Physically degraded wastelands are characterized with gravelliness; dominated by coarser fragments such as sand and silt; deprived of soil fines –silt and clay; and depleted of nutrients especially nitrogen and phosphorus. Thus, the overall fertility and hence, the productivity of wastelands are very much limited and the soil mass provides only physical support for the growing vegetation. The efforts made on the establishment of vegetation on wasteland with fertilizer supplementation and physical water harvesting structures may be ineffective due to coarser nature of soils. As an alternative, the nutrient rich organic wastes generated in urban and agro-industrial centres may be applied to improve the soil fertility and for the establishment of vegetation on wasteland. Thus, synchronization of nutrient depleted situation in wasteland and nutrient toxicity in urban areas may be attempted in an effort to conserve the resource from degradation. Based on these facts and observations, it was attempted to study the influence of application of nutrient rich organic wastes on soil physical and chemical properties and on the growth of tree species under wasteland conditions. The following were the objectives of the study carried out at University of Agricultural Sciences, Bangalore and Karnataka State Council for Science and Technology, Bangalore, Karnataka.

- To characterize the wastelands in terms of physical and chemical properties as soil
limiting factors in afforestation programme
- To characterize domestic and agro-industrial organic wastes for suitability as
nutrient source in afforestation programme
- To evaluate the changes in physical and chemical properties of wasteland soils
due to organic wastes application
- To evaluate the growth performance of tree species due to organic wastes
application in wastelands

II. REVIEW OF LITERATURE

Utilization and conservation of resources are the most important aspects of national development. In most cases, the poor quality of resources and environmental costs associated with the application restricts their utilization. A typical example appears to be the poor quality of land resources in physically degraded wastelands. The soil nutrient status remains low which in turn restricts the plant growth. Thus, the nutrient depletion / deficiency appear to be a serious issue in wastelands accounting for half of the country’s total geographical area. In contrast, the urbanization and industrialization processes, as part of the developmental events, are generating large quantities of waste materials. Fortunately, the generated wastes are rich in organic matter and nutrients, but may be contaminated with toxic organic and inorganic compounds. Incidentally, the wastes generated from agro-based industries are less likely to be contaminated with such toxic compounds.

Two contrasting situations of nutrient depletion / deficiency in wastelands and nutrients at toxic levels in municipal and agro-industrial wastes exist simultaneously on a regional scale. The review available on wastelands there distribution, features, characteristics, restoration strategies and organic wastes, their sources, quality, manurial value, risks associated with land application and their effect on soil properties; and finally, performance of tree species with sludge application are presented separately under different headings in this chapter.

2.1. Wastelands: Definition and Features

In general, wastelands may be referred as physically and /or chemically deteriorated lands which are ecologically unstable and economically unproductive. They are also referred as derelict lands characterized with low fertility status due to severe degradation. The National Wasteland Development Board (NWDB, 1985) suggests that any land which is not producing green biomass, consistent with the status of soil and water may be considered as wasteland. As per the definition of ICAR, the wastelands are those lands, which are not being utilized for their full potential due to negligence or due to degradation (Anonymous, 1987). Wastelands may also be defined as those lands, inclusive of both cultivable and uncultivable lands, which are of low productivity (Anonymous, 1985).

The soil degradation may be physical, chemical and / or biological in nature. The destruction of soil structure, compaction, reduction in infiltration rate, depletion of soil organic matter, reduction in biomass carbon, salt imbalance and buildup of soil borne pathogens etc are some of the factors which result in soil degradation (Lal and Stewart, 1992). In addition, anthropogenic activities such as deforestation, overgrazing, tillage methods, etc would also lead to soil degradation. Inefficient management, misuse and / or over exploitation of lands may cause further degradation. Thus, the adverse changes in soil properties ultimately degenerates the land productivity.

In India, the wastelands are largely formed due to physical degradation. The finer fragments are mostly lost along with the runoff water and thus, the coarse fragments dominate the soil texture. The loss of clay, silt and soil organic matter make these wastelands deprived of nutrients (Bradshaw and Chadwick, 1980). Nutrient deficiency, especially, nitrogen and phosphorus are common as the soil has little capacity to retain inorganic forms of nutrients (Atkinson et al., 1991). Due to these unfavorable conditions, biomass production is affected negatively. Stressed climate, stumpy / bushy vegetal cover, lack of moisture, poor soil quality, etc are some of the important features of physically degraded wastelands, and they are also discussed in the coming sections.

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Figure 1: Distribution of Wastelands in India (Wasteland Atlas of India, 2000).

2.2. Extent of Wastelands

In India, there are varied estimates on the extent of wastelands and they are attributed to inadequacy of sound and non-uniform criteria adopted in defining the state of degradation. Das (1985) has reported that, out of 329 M ha of the country’s total geographical area, the total wasteland constitutes about 170 M ha. In a report of National Commission on Agriculture, it is documented that nearly 175 M ha of land has low productivity (Anonymous, 1984). However, Sehgal and Abrol (1994) have reported that an area of 187.8 M ha (57 % of total) are affected by various land degradation processes. According to an FAO estimate, about 50 % of the total geographical area is under various degradation hazards and the land degradation has expanded at an annual rate of 2.1 M ha (Anonymous, 1986). The extent of land degradation varies from one state to another, depending upon the geographical features, soil characteristics, rainfall, land use, land management practices etc. Large extents of wastelands are mainly distributed in the states of Rajasthan, Madhya Pradesh, Maharashtra, Uttar Pradesh, Gujarat, Andhra Pradesh and Karnataka. The state of Rajasthan has large tracts (37 M ha) followed by Madhya Pradesh, while Tripura has least degraded lands (Wasteland Atlas of India, 2000). The distribution of wastelands in India is presented in Figure 1.

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Figure 2: Distribution of Wastelands in Karnataka

Based on the NRSA survey report, out of 1,91,791 sq. km of total geographical area, the wastelands in Karnataka constitute about 20,839 sq. km (10.87 %). The large tracts of wastelands are spread mainly in Tumkur, Bellary, Bangalore rural, Chitradurga, Bijapur and Kolar districts (Figure 2). Tumkur district is having large percentage followed by Bellary and least percentage of wastelands is in Coorg district (Wasteland Atlas of India, 2000). The wastelands are mainly formed due to soil erosion by water in southern parts (red soils) whereas salinity is the major cause for land degradation in northern parts (black soils) of Karnataka.

2.3. Categories / Forms of Wastelands

The wastelands are nothing but less productive and deteriorated lands formed due to physical, chemical and / or biological degradation. Thus, the wastelands may be categorized broadly based on the causes of degradation as physically degraded, chemically degraded and biologically degraded lands. The extent and type of degraded lands in India are presented Table 1. The ICAR (1990) has also categorized the wastelands into culturable and unculturable wastelands. Culturable Wasteland is one which is capable of or has the potential for the development of vegetative cover and is not being used due to different constraints. The area under rock out crops and snow covered land use types are excluded. Unculturable wastelands are lands, which cannot establish and support any vegetative cover. Thus, the wastelands have been categorized into eroded, gullied and ravine, rocky, glacial, saline lands etc., based on the physical appearance of the land, soil chemical properties and biomass availability. However, in our country, the eroded lands constitute the major portion with 150 M ha (Bali, 1985; Das, 1985).

Table 1: Different forms and extent of degraded lands

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In India, water erosion is one of the major causes of soil degradation and is affecting about 47.2 per cent of the total area (Abrol, 1994). It is estimated that the erosion alone results in the loss of about 6600 million tonnes of top fertile soil annually (Singh et al., 1994), which is nearly four times the permissible soil loss of 8 million tonnes of nutrients and 3 million tonnes of food grains (Dhruvnaryana and Ram Babu, 1983). The total OM loss through eroded sediment varied between 430 and 5200 kg ha-1, the total -N loss ranged between 15.30 and 157.64 kg ha-1, the total available - P loss varied between 0.82 and 12 kg ha-1 and the total - K ranged between 0.21 and 7.3 kg ha-1 (Majaliwa et al., 2001). As the present study is restricted to the wastelands of Karnataka formed due to water erosion, the review is mostly restricted to causes, features and strategies for reclamation of physically degraded lands.

2.4. Features of Eroded Lands

In general, the eroded lands are of low fertility having low organic carbon and other essential nutrients. The loss of silt, clay and soil organic matter along with watercourse make these lands further deprived of nutrients. The nutrient retention capacity of these wastelands is also low due to highly porous nature of soils (Bradshaw and Chadwik, 1980). Thus, the productivity is severely affected due to poor nutrient supply because of low organic matter and clay content. The loss of soil clay and organic matter influence the water and nutrient availability in physically degraded lands (Bernard, 1982; Lal, 1996). There are also reports of decline in soil productivity and crop yields due to diminished nutrient supply and low soil water storage capacities (Hadda, 1983; Sur and Sadhu , 1995). The general features of the wastelands are depicted diagrammatically in Figure 3.

Eroded Wasteland

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*Compiled from Bradshaw and Chadwick (1980); Jordan (1985); Lugo (1987); Bradshaw (1989)

Figure 3: A flow diagram on the general features of eroded wastelands*

2.4.1. Physical Features:

Poor soil structure, high bulk density, less pore space, shallow depth, steep slope, low productivity, high leaching, stoniness are some of the important physical features of degraded lands (Bernard, 1982). The loss of soil fines namely clay, silt and organic matter along with runoff water have resulted in physical degradation. The loss of organic matter decreases the aggregate stability and hence the soil structure (Tisdale et al., 1978; Bhatia and Vardani, 1982). The soil moisture characteristics - water holding capacity, infiltration rate, available soil moisture content etc are also severely influenced in these soils (Atkinson et al., 1991) . Generally, the bulk density of a typical red soil is 1.30 g cc-1 whereas the physically degraded lands dominated with coarse fragments possess a bulk density value of 1.6 + 0.15 g cc-1 (Singh and Om Prakash, 1985). Similarly, the water holding capacity of these eroded soils are much less (30.2 %) compared to that of a productive red soil (39.6 %). It is well documented that the soil moisture retention capacity is influenced by the amount of soil organic matter, porosity and bulk density (Biswas and Ali, 1969).

2.4.2. Chemical features:

Wastelands are typically poor in organic matter and plant nutrients, especially nitrogen and phosphorus (Sanchez, 1976; Jordan, 1985). Soil erosion is one of the major constraint with respect to nutrient availability (Lugo, 1987; Hadda et al., 2000). During the soil erosion process, the nutrients are lost by both dissolution and as physical constituents (in adsorbed and mineral forms). In addition, it affects the soil quality and its ability to buffer loss of nutrients along with water holding capacity (Atkinson et al., 1991; Chanakya and Nagaraja, 1995). Generally, the soil organic carbon in eroded land is less than 0.5 per cent, it is due to loss of organic matter along with soil mineral matter (Lal and Stewart, 1992). Hadda (1983) and Sur and Sadhu (1995) have observed that, nitrogen and phosphorus content decreased in eroded lands compared to un-eroded lands by 81.3 and 64.8 % respectively.

In contrast, Singh and Om Prakash (1985) studied the wasteland characteristics in Western Himalayan region and soil characteristics were reported that, the organic matter and total nitrogen were medium ranging from 1.93 to 1.45 and 0.143 to 0.115 per cent at 0-20 cm and 20 – 45 cm depths respectively. The available phosphorus was high in surface (86 kg ha-1) and medium in sub surface (38.7 kg ha-1). The available potash was low in both the layers of the profile, it ranges from 94.1 kg ha-1 in the upper layer and 81.3 kg ha-1 in the deeper layer. The secondary and micronutrients availability also decreases due to decrease in organic matter. In addition, some of the degraded soils were having appreciable quantity of heavy metals also. However, the nutrients deficiency can be improved by encouraging organic matter build up in the ecosystem, which can replenish the shortage of plant nutrients (Bradshaw, 1984).

2.4.3. Ecological features:

The biomass productivity and biomass turnover among wastelands are much lesser compared to that of other land use systems. A stumpy vegetal cover, a stressed climate, thorny bushes, extensive grazing, insufficient time for vegetation to regenerate, etc are some of the significant ecological features of wastelands (Rai, 1999). Low productivity is mainly attributed to poor availability of nutrients and soil moisture (Hadda, 1983). These stresses severely influence both floral and faunal diversity. Extensive removal of vegetal biomass as fodder, fuel and timber purpose further leads to exposure of soil surface for water and wind erosion. Soil surface exposure further influences the nutrient loss. Overall it affects the productivity of the ecosystem.

The nutrient cycles in wastelands are open in nature and thus, prone for huge nutrient losses. There are reports that the nutrient and hydrological cycles in wasteland are asynchronous in nature and thus results in low productivity (Chanakya and Nagaraja, 1994). There is need for improved scientific understandings on which the effective management of degraded resources is possible. The rehabilitation of degraded lands can support people and thus reduce pressure on forest lands (Lovejoy, 1985).

2.5. Need for Wasteland Reclamation

As discussed earlier, wastelands constitute more than half of the country’s geographical area. It is estimated that nearly 78 per cent of the total land is misfit for agriculture and only 22 % of the land is agriculturally suitable on a global scale (Buringh, 1989). Of which, 13 % has low productive capacity, 6 % a medium and only 3 % is characterized with high capacity for intensive production (Varade, 1992). Therefore, utilizing these wastelands for various types of biomass production is crucial in resource conservation. Sustainable management of these natural resources emphasizes the concept of using, improving and restoring the productive capacity of these marginal lands and there by enhance life-supporting processes of soil (Lal and Stewart, 1992; Verma, 2001).

In India, a population of one billion (18 percent of the world’s population) is supported by just 2.4 per cent of the world total land area to serve all human demand. The per capita land available data reveal that, the land availability has decreased from 0.50 Ha in 1950-51 to 0.15 ha in 1999-2000. Thus, rapidly growing population and limited prime agricultural land are the two driving factors that have put greater pressure on the limited land resources (Lal and Stewart, 1992; Ramanna and Chadrakandan, 2001). Therefore, there is need for rational planning and management of land and protection of the environment (Hirekerur et al., 1990).

Restoration of wastelands is of ecological and socio-economic significance and can reduce further degradation of land resources (Lal and Stewart, 1992). In the process of wasteland restoration, there is also scope for creation of huge employment opportunities that can sustain 40 % of the Indian poor population. Therefore, the development of degraded lands may be considered as an essential and one of the important approaches to meet the food and fodder demands sustainably (Saxena, 2000).

2.6. Strategies for Wasteland Restoration

The scientific community has developed several strategies to restore / rehabilitate the degraded lands (Verma et al., 2004). The soil productivity as a function of management practices over time has been well documented and has been presented in Figure 4 (Lal and Stewart, 1992). The soil productivity may degenerate or improve over time and it is presented in the form of a flow chart (Figure 4). The soil productivity may get degenerated with poor management practices and may lead to erosion, nutrient loss, water logging, acidification, salinization etc. The same can be reversed by adopting good management practices. However, the degradation beyond a critical value may reach irreversible point even with intensive restoration practices. Thus, proper land use planning plays a vital role in the overall wasteland development (Ramanna and Chandrakandan, 2001; Saxena, 2000).

The methods of restoration may be grouped into physical, chemical or biological depending on the mode of restoration strategies and have been discussed in the following paragraphs.

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Source: Bradshaw and Chadwick (1980); Jordan (1985); Bradshaw (1989)

Figure 4: Pictorial representation of soil degradation process and soil conservation measures

2.6.1. Physical Restoration

Soil and water conservation methods are given top priority in wasteland restoration and such strategies are referred as physical restoration (Lal, 1996; Hadda et al., 2000). Both, conservation of runoff water and induced soil loss could be prevented by erecting physical structures across the water flow. Erection of check dams and gully plugs; digging of contour trenches and moisture pits; cultivation practices; soil / stone bunding and vegetative barriers along the contours etc would ultimately reduce runoff velocities and check soil erosion. Excavation of contour furrows tends to alter runoff / rain water utilization pattern by increasing the soil moisture content. The structures built or practices adopted to prevent soil loss in turn also help to conserve water by encouraging infiltration into the soil (Nadadur, 2001).

The soil physical properties of wastelands can be improved by increasing the soil organic matter content through vegetation. The increase in soil organic matter could also improve both maximum water holding capacity and infiltration rates (Brinck et al., 1988; Bradshaw, 1984). The velocity of runoff water on soil surface could also be reduced substantially with vegetal covers, which in turn reduce soil loss (Fryrear, 1985). The improvement in soil structure due to increase in soil organic matter helps to improve porosity and reduces soil bulk density (Pagliai et al., 1981; Chaussod et al., 1985; Singh and Om Prakash, 1985).

2.6.2. Chemical Restoration:

Nitrogen and Phosphorus are always scarce in degraded lands until the organic matter decomposition in the ecosystem is sufficient to supply new growth (Bradshaw, 1984). The nutrient conservation and enrichment practices such as enhancing soil organic matter, soil fertility improvement etc are given priority for the enhancement of soil quality (Bradshaw and Chadwik, 1980; Lal, 1996; Hadda et al., 2000).

Similar reports were also made by Sanchez (1976) and Jordan (1985) suggested that the use of chemical fertilizers could be introduced to overcome the nutrient deficiency. However, supplying of nutrients through fertilizers over large areas is highly expensive and often impractical. As the nutrient retention capacities of the degraded lands are low, the applied nutrients may be lost from the soils. In this situation, application of nutrient rich organic wastes are the best alternatives for wasteland restoration (Nagaraja, 1997a). Application of chemical fertilizer along with organic wastes to degraded lands was also suggested by Lal and Stewart (1992). Thus, the use of agro-industrial and municipal sludge would play a greater role in wasteland restoration (Nagaraja, 1997a).

The cost of nutrients have increased substantially and is likely to increase further due to increase in energy sources and raw materials demand. The organic wastes are known for their manurial value and also in improving the soil fertility and thus, the application of less expensive, nutrient rich industrial and domestic wastes appear to be the best alternative for wasteland situations / reclamations (Pradeep, 1993).

2.6.3. Biological Restoration

Biological restoration comes as another alternative for restoration of wastelands and serves as a buffer. Presence of low vegetal cover on the wastelands makes it more susceptible for wind and water damages resulting in accelerated erosion, which leads to nutrient depletion. Thus, vegetation establishment is the most viable alternative practice for wasteland restoration. Establishment of trees on wastelands is more sustainable compared to grain production due to their abilities to tolerate adverse agro-climatic conditions. Considering the poor productivity of land, nature of risk involved, employment potential, demand for the outputs and overall economic growth, introduction of tree planting seems to be the most appropriate technology for wastelands development and utilization (Nagaraja, 1997a; Bhaskar, 2001). Thus, vegetation establishment appears to be the most viable solution in wasteland reclamation and it can be viewed as best ecological test for the success of wasteland reclamation (Logan, 1992).

There are number of reports indicating the beneficial effects of the vegetation establishment on soil properties (Banerjee et al., 1985; ICAR, 1990; Saxena, 2000). The studies have indicated that vegetation helps in soil stabilization, soil organic matter buildup, moderation of pH and improvement of soil fertility (Shukla and Misra, 1993; Rodrigues, 1997). Mulches with grass cover would increase the infiltration rate and allows safe movement of runoff water without consequential erosion (Hadda et al., 2000)

According to Mishra et al. (1976), the adoption of forestry and pastoral systems in Shivalik region had drastically reduced the silt load from 80 tonnes to 3 tonnes ha-1 as runoff. Singh et al. (1994) documented that the introduction of vegetation in sloppy Western Himalaya reduces runoff yield by 50 per cent and soil loss reduced from 11 tonnes to 2-3 tonnes ha-1 per annually. The detailed soil restoration strategies are given diagrammatically (Figure 5).

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Figure 5: Approaches for soil restoration

From the review, it is clear that no single method provides complete solutions in wasteland reclamation. Multiple approaches involving physical, chemical and biological strategies are necessary for successful restoration (Lal and Stewart, 1992). With all these strategies, the large tracts of low productive marginal lands of our country could be improved successfully through afforestation (Mohan Dharia, 2002).

2.7. Organic Wastes as Nutrient Sources in Wastelands Reclamation

The soils of wastelands are highly weathered or leached and impoverished and need external nutrient inputs to meet plant nutrient demand. Incidentally the problem of nutrient availability in wasteland is complex. The nutrient supplementation must be of slow release type and should supply sufficient amount of nutrients for plants growth. From this point of view, the application of organic amendments viz., composts, industrial and domestic wastes / sludges etc would supply nutrients in long run and also enhance soil quality.

The non-availability and cost factors of organic manures forces the policy makers to look for alternative sources. The benefits of applying bulky organic materials to soil are well recognized in crop production (Pradeep, 1993). The increasing number of towns and cities across the country suggests that there is a great scope for valuing organic waste as a resource rather than disposing it of as a waste (Anonymous, 2003a). It also gives cost effective technologies to industries as well as municipal sectors for their disposal. The application of organic wastes helps considerably in maintaining soil fertility by improving the soil physical, chemical and biological properties (Bradshaw, 1984).

Use of municipal sludge in agriculture is not a new concept and is in practice from the time immemorial. However, handling of sewage waste is very complicated from the point of environment. The viable option for safe disposal is through land application i.e. utilization in agriculture and related activities as nutrient source (Hinesly et al., 1972; King and Morris, 1973; Mays et al., 1973). Similar to the municipal sludge, the agro-industries such as distillery, paper, sugar, fruit processing, coir industries etc are also generating large quantities of wastes with rich nutritive value.

Presently, some of the agro-industries are facing problem of disposal of wastes. Utilizing these wastes effectively for agricultural purposes through eco-friendly techniques could be of immense help to the industries (Anonymous, 2003a). Land disposal, which is often considered as a source of pollution can be looked upon as a nutrient source through scientific approach. By looking into these aspects, utilization of these wastes for wasteland reclamation could be an ideal solution as there is no threat of any toxicants entering in to food chain.

2.7.1. Quantum of Production of Organic Wastes

The process of economic development and urbanization have resulted in substantial production of organic wastes rich in organic matter and nutrients. There are several reports on the issue of ill effects of industrialization and urbanization (Lal and Stewart, 1992; Sharma and Kaur, 1996; Veeresh, 2002). However, the above processes appear inevitable and they are part of country’s development. The rate of urbanization decides about the amount of municipal sludge generated (Anand, 2003). Similarly, the product out put from the respective industries determines the quantity of sludge generated from the respective industry (Anand, 1995; Srikanth, 1997). However, due to its voluminous production, the disposal or utilization is a serious problem.

Municipal sludge is one of the organic wastes generated mainly from urban settlements. Municipal sludge is nothing but solid bio-degradable waste generated from sewage treatment plants after primary and secondary sedimentation processes and hence, it is also referred as ‘sewage sludge’. It is generated from wastewater treatment plants. It is estimated that, a population of 1 lakh produces 10 tonnes of municipal sludge per annum (Sabey, 1980). In India, major cities and towns produce approximately 73 million tonnes of sludge annually (NEERI, 1995; Veeresh, 2002). Bangalore city alone produces nearly about 35 metric tonnes of sludge per month (Anonymous, 2003b).

In terms of quality, the municipal sludge contains substantial amounts of organic matter and plant nutrients and thus, possess high manurial value (Pagliai et al., 1981; Atkinson, 1991; Maiti et al., 1992; Pradeep, 1993; Anand, 2004). It also contains smaller to moderate amounts of non-degradable glass, plastic and metal pieces. The presence of beneficial and harmful compounds in the sludge depends on the magnitude of contamination by industries scattered in the cities (Sharma and Kaur, 1996). The adoption of intensive physical separation at the beginning can reduce the non-degradable matter to a large extent.

In addition to urban wastes, agro-based industries such as distillery, sugar, paper, fruit processing, coir, coffee etc also generate substantial quantities of organic wastes. The quality and quantity of sludge produced depends on the raw material used and the treatment process adopted at industry level. In India, there are about 257 distilleries producing about 4.0 metric tonnes of yeast sludge annually (Bose et al., 2002). It is estimated that in the production of 1000 liters of alcohol, 13000 liters of spent wash and 3800 kg of sludge are produced. The solids that are left after the evaporation of spent wash is called distillery sludge which possess appreciable quantities of nutrients (Sweeney and Graetz, 1988). The distillery sludge is an amorphous, sticky, white solid byproduct with pungent odour. Based on its origin, one can say that it is less likely to contain any toxic compounds or heavy metals. However, the toxic levels of salts can not be ruled out (Bose et al., 2002).

Paper industry is another large group of wood based industries in India and it is of great concern from the point of environment and forests. It is estimated that, one Tonne production of paper generates about 3.2 Tonnes of solid wastes (Bhattacharyya et al., 2004). The solid wastes are in the form of bamboo and wood dust, hypo sludge, lime sludge, ETP (Effluent Treatment Plant) sludge, pulp wastes of non-cellulolytic material etc. The sludge generated at effluent treatment plant is considered to be an ameliorative agent and can be used as an additive / soil amendment (NEERI, 1995). The qualitative analyses indicate that, the sludge is made of cellulose, hemicellulose and lignin along with nutrients containing organic compounds.

In India, sugar industries form the second largest chain of agro-based industries with a total number of about 579 industries (Ananthakumar, 2002). Apart from sugar, they also produce pressmud and molasses as byproducts. They produce about 5.8 m T of pressmud annually (Joshi and Prabhakarasetty, 2005). Pressmud is a soft, spongy, amorphous and dark brownish white material containing sugar, fiber, coagulated colloids including cane wax, albuminoids, inorganic salts, cellulose, soil particles etc. It is also known as filter cake with good nutrient value and well recognized as an organic manure for agricultural purpose (Virendra Kumar and Mishra, 1991). Based on the nutrient status and stages of production, pressmud has been categorized in to two types namely Sulphitation Pressmud (SPM) and Carbonation Pressmud (CP). The clarification process with the help of lime and sulphur dioxide produces sulphitation pressmud with higher nutrient content along with high organic matter. Similarly, in carbonation process calcium carbonate is produced along with other impurities and is known as carbonation pressmud (Yadav, 1992).

The conventional Farm Yard Manure (FYM) is the largest source of nutrients in our country and is in use from ancient times. The FYM availability has gone down significantly and is claimed to be due to drastic decline in bovine population (Shinde, 1992). Mechanization of cultivation practices and usage of dung as alternative source for fuel have further reduced its availability as manure. The excess demand and diminished production resulted in scarcity of FYM and has to led to exploration of other alternative sources (Shinde et al., 1993; Joshi and Prabhakarasetty, 2005).

2.7.2. Waste Disposal through Land Application

As discussed in earlier section, the wastes are generated in substantial quantities in and around cities from both domestic households and industrial units. Increased production of industrial commodities has led to large production of solid organic and inorganic wastes (NEERI, 1995). Due to their bulkiness, the disposal has become a serous problem. In some cases, they are permitted to take away and use them as nutrient and / or fuel alternatives (Bhattacharyya et al., 2004). Generally, they are dumped at pre-determined sites as land fills or disposed on agricultural and non-agricultural lands. Non-availability of such land around cities for disposal has aggravated the situation further. In general, the solid wastes generated in India, is largely disposed as land fills especially in low lying areas as a filling material. There are also reports of other methods of disposal such as incineration, dumping in to ocean, etc which pose much severe stress on the environment (Sharma and Kaur, 1996). Thus, land application was considered as one of the soft option (Pradeep, 1993).

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