Use chemical fertilizer at least
Chemical Fertiliser
RESOURCES
R. Innes, in Encyclopedia of Energy, Natural Resource, and Environmental Economics, 2013
Fertilizer taxes
By raising chemical fertilizer prices, a fertilizer tax raises the opportunity cost of excess manure applications, those applications for which fertilizer substitution benefits are low. Excess manure applications are thereby deterred (Innes). In particular, the tax prompts the facility to lower the extent of excess application close to the facility, where applications are greater and marginal substitution benefits are smaller, by shifting manure to more distant farmland where applications are smaller and substitution benefits are greater.
To elaborate, consider the von-Liebig–Paris (fixed coefficients) production technology with multiple nutrients, each with corresponding production ‘kinks’ (beyond which more of the nutrient does not promote crop growth). Manure contains a portfolio of nutrients that does not exactly match the production function's relative ‘kink’ points; hence, as manure application expands, more and more nutrients reach and surpass their corresponding kinks. Now let us consider the operator's choice between applying an extra pound of manure at two alternate locations: (1) close to the facility and (2) at the edge of the farm, where no manure has yet been applied. At the farm's edge, every extra nutrient delivered by the manure translates into that much less chemical fertilizer that the operator needs to purchase; when the chemical fertilizer price goes up in tandem with a fertilizer tax, the value of this fertilizer substitution also goes up. Close to the facility, however, the operator is already applying manure excessively (because of the logic described earlier) and using little chemical fertilizer (because most of the nutrients exceed their ‘kink’ points); here, the extra manure yields value by saving costs of ‘transporting’ the manure further from the facility, by substituting for some (but not all) chemical fertilizer counterparts to the manure nutrients, and possibly by providing additional (beyond the kink) crop nutrients. Clearly, this value is affected less by the price of chemical fertilizers than is the value of application at the edge of the farm because manure applications substitute for fewerchemical fertilizers close to the facility. An ad valorem fertilizer tax thus leaves the value of ‘close’ applications changed relatively little, and thereby raises the operator's incentive to shift manure from the close location, where application is excessive, to the farm's edge, where application is not excessive.
Because the nutrient runoff from manure application – and the environmental costs of this runoff – rise with the extent of excess application, the ‘evening out’ of applications leads to reduced levels of runoff and environmental damage. A positive fertilizer tax can thus make facilities act as if they face some of the environmental costs of their manure applications, and increase economic welfare as a result.
Exploring soil responses to various organic amendments under dry tropical agroecosystems
Rishikesh Singh, ... A.S. Raghubanshi, inClimate Change and Soil Interactions, 2020
21.9 Conclusion and Possible Recommendations
The intensive chemical fertilizer-based agriculture has resulted in the deterioration of environmental quality and soil systems. Organic amendments lead to an improvement in soil physicochemical and biological properties of tropical soils. Organic amendments potentially increase the soil organic C level of degraded soils that further leads to improvement in overall soil quality. Increased microbial biomass and soil respiration have been reported by several studies under organically amended tropical soils due to the interaction of soil temperature and moisture. Moreover, the relative availability of inorganic N pools has been identified as the emerging determinant of SOC dynamics in dry tropical ecosystems. In addition, a few negative impacts and constraints are also identified. Therefore future research on organic amendments to tropical soils should focus on the following:
- 1.
To develop measures for easy availability of organic fertilizers to the farmers at a minimal or subsidized cost
- 2.
Research on further minimizing the observed global warming potential of organic amendments by developing the appropriate scheduling of application methods
- 3.
Combined application of organic amendments with reduced chemical fertilizer inputs needs further exploration in terms of priming effect and yield components
- 4.
Exploration of the relative availability of nutrients under organically amended soil system for managing SOC dynamics under changing climate scenario
- 5.
Exploring the behavior of organic amendments as slow-release fertilizer either sole or in different combinations for improving the NUE.
Sustainable Composting and Its Environmental Implications
Quan Wang PhD, ... Jonathan W.C. WongPhD, in Sustainable Resource Recovery and Zero Waste Approaches, 2019
Agriculture and Economic Benefits of Compost
The application of chemical fertilizers can increase the crop yields quickly, but they also could cause soil hardening and decrease soil organic matter and pH after a long period of application, resulting in loss of soil productivity [55]. However, most proportion of the chemical fertilizers will be ran off or leached due to rain and heavy irrigation, consequently leading to environmental pollution and lower fertilizer effect. Compost is produced from organic waste, which not only contains organic matter but also is rich in micro- and macronutrients. The utilization of compost as a soil fertilizer or amendment could restore the soil quality and improve soil structure and fertility, which not only serves an important role in agricultural production but also is of great significance for improving the ecological environment [56]. Nowadays, using compost as a substitute to chemical fertilizer has become a global consensus. The application of compost could promote soil productivity and improve the crop quantity and quality, as well as increase the income of the farmers.
SOIL FERTILITY AND PLANT NUTRITION
Daniel Hillel, in Soil in the Environment, 2008
HISTORICAL REVIEW OF SOIL FERTILITY MANAGEMENT
Traditional farming systems generally included a period of fallow in the cropping sequence to help restore soil fertility. The biblical injunction, for example, required fallowing the land every seventh year to let the land rejuvenate (Deuteronomy 15). From at least the time of Cato the Censor (234–139 b.c.e.), the Romans were also aware of the need to boost soil fertility by fallowing, as well as by crop rotation, liming acid soils, and adding manure. In medieval Europe, between one-third and one-half of the arable land was left fallow.
However, increases in population density gradually led to a reduction in the fractional area left fallow, until the custom of fallowing nearly disappeared. Spreading animal manures in the field, as well as inclusion of leguminous crops, helped to add nitrogen, a principal nutrient, to the soil. Such legumes as clover, beans, and peas can improve soil fertility because of their symbiotic association with specialized bacteria that attach themselves to plant roots and that can absorb elemental nitrogen from the atmosphere, a remarkable feat that higher plants cannot perform on their own. In the rice farming areas of Asia, the occurrence of blue-green algae (cyanobacteria) in the flooded rice paddies similarly helped to supply nitrogen to the soil, and the application of organic residues, including human wastes, further helped to maintain soil fertility.
As agricultural production was further intensified, with multiple cropping per year and with more nutrients removed from the fields as crops were harvested, extensive areas began to experience a progressive loss of soil fertility resulting from the depletion of essential nutrients. Consequently, yields began to decline. Some farmers were desperate enough to glean animal and human bones from the great battlegrounds of Europe (Waterloo, Austerlitz, etc.) in order to crush and spread them on their gardens and field plots. In 1840, Justus von Liebig of Germany, called the “father” of soil chemistry, proved that treatment with strong acid increased the availability of bone nutrients to plants.
Necessity impelled the development of artificial fertilizers, which are chemical substances containing, in forms readily available to plants, the elements that improve the growth and productivity of crops. The three major nutrient elements that a crop needs are nitrogen, phosphorus, and potassium. (Other “minor” elements are required in much smaller amounts.)
The first artificial fertilizer was superphosphate, invented by the English agricultural chemist John Bennet Lawes. In 1842, he patented a process of treating phosphate rock with sulfuric acid to make the phosphate soluble, thus initiating the chemical fertilizer industry. Lawes later founded the world's first agricultural experiment station on his own estate of Rothamsted, not far from London. Potashfertilizer could be extracted in readily soluble forms, such as potassium chloride, from geological deposits found in several countries, including Germany, France, the USA, Canada, and from the brine of the Dead Sea.
The problem remained how to supply sufficient nitrogen to satisfy crop needs. Paradoxically, plants live in a veritable ocean of nitrogen—some 79% of the atmosphere—but are unable to assimilate it in its elemental form. During the latter part of the nineteenth and early part of the twentieth centuries, the major source of nitrogenous fertilizers were the saltpeter (sodium nitrate) deposits of Chile, and the guano (accumulated dung of seabirds) in the islands off the shore of Peru. The need to mine and transport these substances across the ocean, and the frequent disruption of international trade by wars in the twentieth century, made these fertilizer sources too expensive and insecure.
The long-range problem of supply was solved just before World War I by the work of Fritz Haber and Carl Bosch in Germany. Haber discovered a way to synthesize ammonia virtually from air and water, by getting elemental nitrogen to combine with hydrogen under high pressure and moderately high temperature. The process, as subsequently refined and industrialized by Bosch, requires energy that is generally obtained from fossil fuels.
The advent of chemical fertilizers marked a revolutionary change in modern agriculture. Along with improvement of crop varieties and of methods to control diseases and pests, as well as to prevent soil erosion, the development of fertilizers brought about a dramatic increase in crop yields. In a real sense, it fulfilled Jonathan Swift's observation quoted at the beginning of this chapter. On the other hand, it accelerated the spiral of population growth, enhanced by modern medicine and hygiene. Moreover, the excessive use of fertilizers eventually began to cause environmental pollution and degradation. Thus, we have yet another example of how an innovation designed to alleviate one problem—if applied injudiciously—may beget other problems1.
Reactive Nitrogen in Agroforestry Systems of India
A. Ram, ... B.P. Meena, in The Indian Nitrogen Assessment, 2017
Through Trees
The introduction of chemical fertilizers to compensate N deficiency has created a lot of environmental problems in different ecosystems. Nature offers better solutions to tackle the environmental issues created by chemical fertilizers. BNF is one of the best sustainable alternatives to conventional N fertilizers that enhances nutrient cycling with in the soil environment. The total annual terrestrial inputs of N from BNF as given by Burns and Hardy (1975) and Paul (1988) range from 139 to 175 Tg of N, with symbiotic associations growing in arable land accounting for 25–30% (35–44 Tg of N) and permanent pasture accounting for another 30% (45 Tg of N).
Over 600 tree species have been reported as N-fixing and integration of these trees can reduce resource competition among different components in agroforestry. The contribution of leguminous trees for building up N in degraded soils through BNF is well recognized as an important component of the ecosystem service of nutrient cycling (Uthappa et al., 2015). There are significant differences in estimates of BNF in trees, ranging from high rates up to 500 kg N2 ha−1 year−1 (Leucaena leucocephala) to low rates 13 kg N2 ha−1 year−1 (Gliricidia sepium) as reported by Young (1989); Antangana et al. (2014); Rao (1990). Dommergues (1987) have classified the tree species into two broad categories on the basis of N-fixing potential. Species with a high N-fixing potential (in the range of 100–300 kg N ha−1 year−1 and more), e.g., Acacia mangium, Casuarina equisetifolia, L. leucocephala and species with a low N-fixing potential (<20 kg N ha−1 year−1), e.g., Acacia albida, A. raddiana and A. senegal. The agroforestry systems in tropical countries are designed on the basis of BNF trees which can act as fertilizers to annual components. Table 14.1 illustrates the BNF trees, with their N-fixation potential in soil, so that they can be used for designing agroforestry system on the basis of the N requirement of annual components.
Table 14.1. Biological N-Fixing Potential of Leguminous and Actinorhizal Trees and Shrubs in Agroforestry System
| Tree Species | N-Fixation (kg ha−1 year−1) |
|---|---|
| Leguminous trees | |
| Acacia mangium | 128 |
| Acacia mearnsii | 200 |
| Albizia lebbeck | 260 |
| Erythrina sp. | 57–66 |
| Faidherbia albida | 20–50 |
| Gliricidia sepium | 13–50 |
| Grevellea robusta | 100–300 |
| Inga edulis | 35–40 |
| Leucaena leucocephala | 100–500 |
| Prosopis species | 25–26 |
| Sesbania sesban | 260–330 |
| Actinorhizal trees | |
| Allocasuarina littoralis | 218 |
| Alnus acuminata | 279 |
| Alnus glutinosa | 40–53 |
| Alnus nepalensis | 30–120 |
| Alnus rubra | 85–320 |
| Casuarina equisetifolia | 60–110 |
| Coriaria arborea | 192 |
| Ceanothus velutinus | 4–100 |
Adapted from Young, A., 1989. Agroforestry for Soil Conservation. CAB International, Wallingford; Rao, D.L.N., Gill, H.S., Abrol, I.P., 1990. Regional experience with perennial sesbania in India. In: Perennial Sesbania Species in Agroforestry, pp. 189–198; Atangana, A., Khasa, D., Chang, S., Degrande, A., 2014. Tropical Agroforestry. Springer; Russo, R.O., 2005. N-fixing trees with actinorhiza in forestry and agroforestry. In: Wenzer, D., Newton, W.E., (Eds.), Nitrogen Fixation in Agriculture, Forestry, Ecology and the Environment; pp. 143–171.
Among N-fixing trees, many legume species are nodualted by Rhizobium, while a few nonleguminous species are nodulated by Frankia (about 200 plant species covering 19 genera and 8 families). Almost all genera are nodulated by Frankia in the Casuarinaceae, Coriariaceae, Eleagnaceae, Datisticaceae, and Myricaceae families, whereas nodulation occurs occasionally in Betulaceae, Rhamnaceae, and Rosaceae (Benson and Clawson, 2000).
Actinorhizal-Frankia symbiosis can be found in a vast range of climates and have the potential to fix up to 320 kg N ha−1 year−1(Table 14.1). Additionally, these species tend to be aggressive colonizers and can survive in harsh conditions. However, the integration of these trees into agroecosystems is an area of research that remains largely unexplored (Batiano, 2012). Actinorhizal trees play vital role as woody perennials in agroforestry systems. One of the most known species of actinorhizal trees is Casuarina which is used for firewood production as a component of a multipurpose agroforestry plantation, or when large plantations are interplanted (Taungya system) with agricultural crops. Paschke and Dawson (1992) described some of the actinorhizal tree species and their potential role in agroforestry; Alnus (timber and pulpwood); Elaeagnus spp. (nurse plant); and Elaeagnus, Shepherdia, and Purshia spp. (soil reclamation).
Management of biologically fixed N in the agroforestry system is most crucial and many studies have been carried out in order to enhance the nitrogen use efficiency. The species or provenances selected should have the highest N-fixing potential, be tolerant to adverse environmental constraints, and resistant to pests. N-fixing efficiency also varies with tree density and climatic conditions. To achieve maximum N-fixing potential, optimum pH, adequate phosphorus, calcium, and molybdenum levels need to be maintained. Secondary effects such as allelopathic interferences and development of microorganisms pathogenic to companion crops should not be overlooked.
In the recent past, various researchers have estimated the area of agroforestry in India. The estimates range from 11.15 m ha (FSI, 2013) to 25.32 m ha (Dhyani et al., 2013). Recently, Rizvi et al. (2014) have also estimated agroforestry area (17.45 m ha) for different states using Bhuvan landuse/land cover data. For calculating the number of BNF trees ha−1, agroforestry data of eight Indian states (Punjab, Haryana, Uttar Pradesh, Bihar, West Bengal, Gujarat, Rajasthan, and Tamil Nadu) were used (NRCAF, Annual Report, 2014; CAFRI, Annual Report, 2015; Ajit et al., 2016). The average N-fixing capacity (7.46 kg N ha−1 year−1 tree−1) was derived by taking the average of all BNF trees in all these eight states and their N-fixing potential (Diagne, 1996; Roskoski et al., 1986; Dreyfus et al., 1987; Sanginga et al., 1986). The average number of BNF trees was 1.5 trees ha−1, fixing about 11.18 kg N ha−1 year−1. Therefore, BNF trees in an area of 17.45 m ha in India can fix N up to 0.195 Tg year−1 (Table 14.2).
Table 14.2. Preliminary Estimates of Biological Nitrogen Fixation Through Trees in AFS in Indiaa
| State/UT | Area Under Agroforestry (m ha) | N-Fixation (t yr−1) |
|---|---|---|
| Andhra Pradesh | 1.67 | 18,704 |
| Arunachal Pradesh | 0.02 | 201 |
| Assam | 0.27 | 2985 |
| Bihar | 0.80 | 8888 |
| Chhattisgarh | 0.70 | 7815 |
| Delhi | 0.01 | 67 |
| Goa | 0.01 | 123 |
| Gujarat | 1.09 | 12,175 |
| Haryana | 0.35 | 3935 |
| Himachal Pradesh | 0.03 | 369 |
| Jammu and Kashmir | 0.09 | 1051 |
| Jharkhand | 0.53 | 5970 |
| Karnataka | 1.29 | 14,456 |
| Kerala | 0.09 | 1051 |
| Madhya Pradesh | 1.35 | 15,037 |
| Maharashtra | 1.92 | 21,421 |
| Meghalaya | 0.02 | 246 |
| Manipur | 0.02 | 201 |
| Mizoram | 0.00 | 45 |
| Nagaland | 0.01 | 56 |
| Odisha | 0.80 | 8989 |
| Puducherry | 0.00 | 22 |
| Punjab | 0.42 | 4696 |
| Rajasthan | 2.05 | 22,930 |
| Sikkim | 0.01 | 89 |
| Tripura | 0.03 | 291 |
| Tamil Nadu | 0.69 | 7692 |
| Uttar Pradesh | 1.97 | 22,036 |
| Uttarakhand | 0.07 | 827 |
| West Bengal | 0.41 | 4528 |
| Other states/UT | 0.73 | 8173 |
| All India | 17.45 | 195,069 |
- a
- Species considered for calculating the BNF through trees: Dalbergia sissoo, Acacia nilotica, Leucaena leucocephala, Albizia procera, Acacia auriculiformis, Prosopis cineraria, Acacia tortilis, Gliricidia sepium.
In order to estimate average litter fall from agroforestry systems, litter fall data of Eucalyptus, Populus deltoides, Acacia tortilis, A. leucocephla, Prosopis cineraria, Dalbergia sissoo, A. nilotica, Alnus nepalensis, Leucaena leucocephala, Bambusa vulgaris, Grewia optiva, Azadirachta indica, Pongamia pinnata, Tectona grandis, Celtis australis, and Albizia procera were considered. Based on literature review (Roy and Nigam, 2001; Yadav et al., 2008; Kaur, 1998; Das and Chaturvedi, 1997; Tripathi et al., 2009; Oladoye et al., 2010; Hariprasath et al., 2014; Panwar and Gupta, 2016; Singh et al., 1999; Manivasakan et al., 2007; Panwar and Gupta, 2015; Gupta et al., 2010; Isaac and Achuthan, 2006), it was found that one tree adds 18.70 kg litter ha−1 year−1. Considering average density of 12.44 trees ha−1 (NRCAF, Annual Report, 2014; CAFRI, Annual Report, 2015; Ajit et al., 2016) in agroforestry, 0.055 Tg of N is added through litter fall to the system.
Photobioreactor–Wetland System Removes Organic Pollutants and Nutrients
Yonghong Wu, in Periphyton, 2017
11.1 Introduction
Human products such as chemical fertilizers, pesticides, herbicides, and plant hormones are often applied in intensive agricultural areas to maintain high yields (Haas et al., 2001). These chemicals usually constitute the majority of nonpoint-sourcepollutants to the downstream surface aquatic ecosystems when they are carried either by runoff or irrigation effluent (Wu et al., 2010a). These are some of the most predominant pollution sources causing eutrophication and harmful algal blooms(Pan et al., 2010). Furthermore, the migration of some natural organic matters, such as polycyclic aromatic hydrocarbons, into aquatic ecosystems poses a hazardous threat to some beneficial animals such as tadpoles (Guo et al., 2007; Novák et al., 2008) and destroys the food web and the balance of the aquatic ecosystem. Thus, the reduction of the inputs of organic contaminants and excessive nutrients into downstream aquatic ecosystems is of practical significance.
Natural organic matter is a complex assembly of organic compounds occurring in natural surface waters. The natural organic matter can directly affect the odor, color, and taste of water as well affect processes in drinking water and wastewater/water treatments (Chae et al., 2015; Cheng et al., 2016). The precursor of trihalomethanes (THMs) after chlorinationof drinking water and wastewater/water treatments often occurs (Han et al., 2015; Peng et al., 2016; Sadrnourmohamadi and Gorczyca, 2015), which is often represented by UV254nm-matter (ultraviolet absorbance at 254 nm) (Wu et al., 2011). Chlorination has been a popular means for disinfecting municipal drinking water and surface water in many countries, including China, for many decades. The addition of chlorine will continue to be the most common disinfection process. The added chlorine reacts with naturally occurring organic matter to form a wide range of undesired halogenated organic compounds, often referred to as disinfection byproducts. Among the most widely occurring byproducts are THMs, haloacetic acids, haloacetonitriles, and haloketones (de la Rubia et al., 2008). Thus, this study investigated natural organic matter and its removal.
Several treatment processes or their combinations are capable of removing natural organic matter from water (de la Rubia et al., 2008). Therefore, some measures have been proposed to decrease the amount of organic contaminants and nutrients in aquatic ecosystems (Dorioz et al., 2006). These measures include (1) the reduction of the production of potential pollutants (e.g., reducing usage of agrochemicals) (Blanchoud et al., 2007), (2) the reduction of the migration of pollutants (e.g., improving irrigation management) (Kay et al., 2009) and (3) the acceleration of the sequestration and degradation of pollutants toward aquatic ecosystems (e.g., buffer zones and wetlands) (Schulz and Peall, 2001). Many specific technologies have been developed for the final treatment in the removal of aromatic compounds, and various measures have been introduced, such as the application of soybean peroxidase (Kinsley and Nicell, 2000), the utilization of ozone and photocatalytic processes (Fabbri et al., 2008), bioremediation via specific aromatic compound-degrading microorganisms(Häggblom, 1992), physical sequestration by clays (Liu et al., 2008), and powdered activated carbon (Dąbrowski et al., 2005). In some cases where microfiltration alone is inadequate, the natural organic matter was often pretreated by coagulation to meet water quality requirements (Jiang et al., 2016; Sillanpää and Matilainen, 2015). To meet specific demand, the application of advanced oxidation processes for the removal of organics from water is gaining importance in water treatment (Ganiyu et al., 2015; Zhang et al., 2016). For example, the utilization of active carbon to adsorb natural organic matter in the final stages of surface water treatment was evaluated (Zhang et al., 2016).
The aforementioned measures/technologies are useful and have great benefits for downstream environments. However, several new, complex problems have arisen due to the introduction of some “modern” farming techniques. For example, aromatic compounds have been brought into the soil with the application of some new pesticides, herbicides, and phytohormones, such as mecoprop [2-(2-methyl-4-chlorophenoxy) propionic acid] (Tett et al., 1994) and auxin (Kelley and Riechers, 2007). These aromatic compounds can move into the downstream aquatic ecosystems through runoff and irrigation. In addition, the long-term applications of chemical fertilizers have caused the degradation of soil quality and the decline of nutrient-holding capacities (Kong et al., 2008). This degradation might lead to excessive dissolved nutrients, such as dissolved nitrogen and phosphorus, flowing easily into downstream aquatic ecosystems, increasing the risk of eutrophication. To reduce the input of these organic contaminants and dissolved nutrients into downstream aquatic ecosystems, these pollutants should be removed by environmentally friendly biomeasures at the downstream catchments of intensive agricultural areas, thus improving the self-purifying capacities of aquatic systems.
We proposed a photobioreactor–wetland system and utilized the technology based on this system in the downstream catchments of an intensive agricultural area in the Kunming region of western China, where the self-purifying capacity had been weakened. To provide an amplified model of the photobioreactor–wetland system at an industrial scale, three additional considerations should be taken into account: (1) the measure should be environmentally friendly, requiring that it not introduce any hazardous materials or artificial chemicals into the environment; (2) the habitats of native flora and fauna should be recovered, and then the self-purifying capacity of the recovered ecosystem should be improved, and (3) the construction and operation of the photobioreactor–wetland system should be simple. The capital and operation costs should be affordable.
Biofertilizers as substitute to commercial agrochemicals
Chandrima Bhattacharyya, ... Abhrajyoti Ghosh, in Agrochemicals Detection, Treatment and Remediation, 2020
Abstract
Biofertilizers are preferred alternatives to chemical fertilizers for improving the overall health status of plants. Besides being environment friendly, biofertilizers showcase other important features, including their sustainability within agricultural soils. During the last century, increasing use of commercial agrochemicals resulted in bioaccumulation of varied contaminants within the agricultural soils and nearby water bodies. Furthermore, studies have confirmed the biomagnification of these chemical entities in different trophic levels through the food chain. Effective and environment friendly means of removal of these contaminants from the ecosystem remain a challenge in sustainable agricultural practice. In the present chapter, commercial agrochemicals that influence the present agricultural practice are discussed in detail. Furthermore, an overview of the plant growth–promoting microorganisms and their role as biofertilizers is highlighted. The concluding part of the chapter summarizes the use of rhizoengineering as a method of choice to favorably alter the soil composition using plant growth–promoting microorganisms. Such an approach might be useful in replacing commercial agrochemicals and facilitating sustainable agricultural practice.
Agricultural Waste and Pollution
R. Nagendran, in Waste, 2011
6 Agriculture and Fertilizers
According to the FAO, chemical fertilizersare the single most important contributor to the increase in world agricultural productivity [17]. Fertilizers containing nitrogen, phosphorus and potassium are viewed as the drivers of modern agriculture. Their use worldwide has been increasing since the onset of the so-called ‘green revolution’. Data in respect of India presented in Table 24.5 bear testimony to this trend, and it is very likely that many other developing and developed countries exhibit similar trends.
TABLE 24.5. All-India Consumption of Fertilizers in Terms of Nutrients (‘000 Tonnes)
| Year | N | P | K | Total |
|---|---|---|---|---|
| 1950–1951 | 158.7 | 6.9 | – | 165.6 |
| 1955–1956 | 107.5 | 13.0 | 10.3 | 130.8 |
| 1960–1961 | 210.0 | 53.1 | 29.0 | 292.1 |
| 1965–1966 | 574.8 | 132.5 | 77.3 | 784.6 |
| 1970–1971 | 1,487.0 | 462.0 | 228.0 | 2177.0 |
| 1975–1976 | 2,148.6 | 466.8 | 278.3 | 2893.7 |
| 1980–1981 | 3,678.1 | 1,213.6 | 623.9 | 5515.6 |
| 1985–1986 | 5,660.8 | 2,005.2 | 808.1 | 8474.1 |
| 1986–1987 | 5,716.0 | 2,078.9 | 850.0 | 8644.9 |
| 1987–1988 | 5,716.8 | 2,187.0 | 880.5 | 8784.3 |
| 1988–1989 | 7,251.0 | 2,720.7 | 1,068.3 | 11,040.0 |
| 1989–1990 | 7,386.0 | 3,014.2 | 1,168.0 | 11,568.2 |
| 1990–1991 | 7,997.2 | 3,221.0 | 1,328.0 | 12,546.2 |
| 1991–1992 | 8,046.3 | 3,321.2 | 1,360.5 | 12,728.0 |
| 1992–1993 | 8,426.8 | 2,843.8 | 883.9 | 12,154.5 |
| 1993–1994 | 8,788.3 | 2,669.3 | 908.4 | 12,366.0 |
| 1994–1995 | 9,507.1 | 2,931.7 | 1,124.7 | 13,563.5 |
| 1995–1996 | 9,822.8 | 2,897.5 | 1,155.8 | 13,876.1 |
| 1996–1997 | 10,301.8 | 2,976.8 | 1,029.6 | 14,308.1 |
| 1997–1998 | 10,901.8 | 3,913.6 | 1,372.5 | 16,187.9 |
| 1998–1999 | 11,353.8 | 4,112.2 | 1,331.5 | 16,797.5 |
| 1999–2000 | 11,592.7 | 4,798.3 | 1,678.7 | 18,069.7 |
| 2000–2001 | 10,920.2 | 4,214.6 | 1,567.5 | 16,702.3 |
| 2001–2002 | 11,310.2 | 4,382.4 | 1,667.1 | 17,359.7 |
| 2002–2003 | 10,474.1 | 4,018.8 | 1,601.2 | 16,094.1 |
| 2003–2004 | 11,077.0 | 4,124.3 | 1,597.9 | 16,799.1 |
| 2004–2005 | 11,713.9 | 4,623.8 | 2,060.6 | 18,398.3 |
| 2005–2006 | 12,723.3 | 5,203.7 | 2,413.3 | 20,340.3 |
| 2006–2007 | 13,772.9 | 5,543.3 | 2,334.8 | 21,651.0 |
| 2007–2008 | 14,419.1 | 5,514.7 | 2,636.3 | 22,570.1 |
| 2008–2009 | 15,090.5 | 6,506.2 | 3,312.6 | 24,909.3 |
Source: Agricultural Statistics at a Glance, 2009, Government of India [18].
Unscientific and overzealous use and application of nitrogenous and phosphorus fertilizers in agriculture have led to the well-known eutrophication of all types of water bodies. Agricultural use of N and P very often lead to problems of ‘non-point’ pollution. Figure 24.4 captures the phases and pathways involved in the process. Data on N and P discharges to surface waters in the United States are available from Ref. [19], and the negative effects of eutrophication on aquatic systems and humans are in Ref. [20].
Figure 24.4. Inputs, outputs and transport of P and N from agricultural land modified after Carpenter et al. [20].
In some parts of the world (e.g., Asia), organic fertilizers derived from animal and human excreta are used to supplement inorganic ones. Their eco-friendly dimension notwithstanding, they are associated with some human and animal health problems. There have been reports, especially from developing countries, of water quality deterioration caused by their discharge into water bodies. Infiltration of nitrates and to a very little extent, phosphates, may contaminate groundwater as well. Volatilizing ammonia may lead to acidification of water and land. Heavy metal fractions occurring in excreta may add to the mess.
From a futuristic view point, there is an urgent need to reverse the trend in N and P flows into and through the agro systems before they reach their ultimate reservoirs. Nitrogen input–output analyses coupled with modeling studies may help agro managers to achieve this (see also Refs. [21, 22]). Other efforts should include urban runoff management, proper understanding and modeling of atmospheric deposition of N, biocapturing of excess N and P in the system, and optimal dosing of nutrients.
Growing algal biomass using wastes
Félix L. Figueroa, ... F. Gabriel Acién, inBioassays, 2018
6.4 Biorefinery and integration of the production and biochemistry processes
Microalgae biomass produced using both chemicals/fertilizers as culture medium or alternatively wastewater from human or animal sources have similar biochemical composition, thus technically they can be used for the same final purpose although regulations avoid the use of microalgae biomass obtained from wastes for direct human uses. Microalgae biomass mainly contains proteins, lipids, and carbohydrates thus different biorefinery schemes have been proposed to valorize the complete biomass [64]. High value compounds contained into the biomass must be first extracted and then the waste biomass can be used for low value applications. Valuable compounds contained in the biomass include carotenoids, polyunsaturated fatty acids, and sterols, among others. In terms of global valorization of the biomass, different schemes can be proposed, from the single production of biogas to the complete fractionation of the major components of the biomass. Whatever the proposed scheme is, two major criteria must be accomplished: (1) most valuable compounds must be first extracted to avoid losses, and (2) mild conditions must be used in each step to prevent decomposition of the remaining compounds. Fig. 6.3 shows a scheme of a biorefinery process for the complete valorization of microalgae biomass (Patent PCT/ES2013/070064).
Figure 6.3. Scheme of a biorefinery process proposed for the complete valorization of microalgae biomass.
According to this scheme the most valuable proteins are first extracted as free amino acids and peptides through enzymatic hydrolysis to produce amino acid concentrates, next the carbohydrates are extracted through thermochemical hydrolysis under mild conditions, to be later fermented to produce bioethanol. The removal of proteins and carbohydrates from the initial biomass increases the percentage of lipid content in the waste biomass, enhancing the yield of the lipids valorization step. Saponificable lipids can be transformed into biodiesel through direct transesterification and the remaining waste biomass is suitable to be used to produce biogas by anaerobic digestion. The optimization of each step allows determining the maximal yield achievable, but it must be taken into account that in each step losses of other compounds can take place. Thus, only a precise optimization of the entire process can define the maximal amount of final products to be obtained. Under optimal conditions the patented process allows for utilization of 66% of the raw material; thus 34% is lost during the processing. This value is higher than when producing biogas from direct biomass; in that case a maximal biomass use efficiency of 62% can be achieved. If only single products are obtained, maximal biomass use efficiency is 30% in production of amino acid concentrates.
Although a large number of biorefinery schemes have been proposed, not all of them are technically or economically feasible. The economy of processing the biomass to obtain valuable products is greatly related to the price of the products to be obtained, and the biomass production costs. Microalgae biomass production costs are largely dependent on the technology used and the final application of the biomass [65]. The coupling of microalgae production with wastewater treatment is the only way to reduce the production costs below €1 per kg−1 [14]. In this scenario the production of low value products such as amino acid concentrates, bioethanol, biodiesel, and biogas is suitable. However, these type of processes must still be validated at the pilot scale to confirm reliability of the technology proposed and overall economy and sustainability of the entire process.
Solid Waste: Assessment, Monitoring and Remediation
A.S. Juwarkar, ... P. Khanna, in Waste Management Series, 2004
VI.7.3.3. Bioreclamation of mine waste using biofertilizers
Realizing the problems of using chemical fertilizers for mine waste reclamation, attention has been diverted to an alternative source, i.e. biofertilizers. The role of biofertilizers in agriculture is well established (Desmukh, 1998; Sharma, 2002). There is a need to transfer these established technologies and practices in establishing forest plantations and reclaiming degraded lands. Potential benefits of microsymbionts such as mycorrhizal fungi responsible for phosphorus absorption, specially on nutritionally poor soils, nitrogen fixers (Frankia) associated with non-leguminous trees, micro-aerophillic nitrogen fixers (Azospirillum) associated with tropical grasses, free living nitrogen fixers (Azotobacter, Beijerinckia and Derxia, etc.) associated with rhizosphere of plants and phosphomicrobials responsible for solubilization and mobilization of phosphate in soil have not yet been fully exploited for wasteland development and forest production. At present evidence is still insufficient to justify the use of inoculants other than Rhizobium for legumes to increase the quality of soil and plants associated with forest.
The essential nature of mycorrhizae for the successful colonization of certain mine wastes was established by the landmark work of J.R. Schramm in the early 1960s. Since that time, research has been expanded to include vesicular–arbuscular (VA) and ericoid mycorrhizae and the development of techniques for inoculating host plants with fungi specifically adapted to coal mine wastes in the harsh conditions of extremes of temperature and low nitrogen. Other limiting factors comprise available phosphorus, and other nutrients such as zinc, copper and ammonium, water scarcityand extremes of pH values.
Schramm (1966) found that nearly all the successful colonizers of coal wastes in Pennsylvania were mycorrhizal. These included species of Pinus, Betula, Populusand Salix, and all of them were ectomycorrhizal.
Marx et al. (1984) used the concept of forming ectomycorrhizae on tree seedlings in nurseries with specific fungi ecologically adapted to the planting site, which was originally developed by Moser and further used by other researchers. Cited successful applications of this technique include improving field performance of Pinus caribaea inoculated with pure culture of Suillus polorans, and Pinus radiata inoculated with isolates of Rhizopogon luteolus, Suillus granulatus, S. luteus and Cenococcum geophilum in Australia. Marx et al. (1984)further refined the Moser's technique and reported good results in inoculating bare-root nursery beds with Pisolithus tinctorius.Mycorrhizal seedlings of P. caribaeainoculated with R. luteolus were more robust, healthy and superior in height and dry matter production than the uninoculated seedlings. Investigations have also shown that inoculation of container grown oak seedlings with specific ectomycorrhizal fungi further improved seedlings survival and early growth in green house and field. Container grown black Oak (Quercus velutina Lam.) and pines seedlings colonized with P. tinctorius and Sawforth Oak inoculated with Thelephora terrestrissurvived and grew better than bare rooted stock on a reforestation site.
The adhesion of soil particles to roots in dry soil has been suggested as a mechanism to increase water conductivity (Coutts, 1982) and it may also function to enhance the movement of mobile ions such as nitrate. Hyphae of VA fungi may extend up to 0.8 m from the root surface (Rhodes and Gerdemann, 1975), but rhizomorphs of Pisolithus may extend 4 m into the soil (Schramm, 1966), a result that suggests ectomycorrhizae are better adapted to long distance transport than VA mycorrhizae.
Ten-year-old untreated coal tips in Scotland were successfully colonized by both grasses and dicotyledonous plants that all but one species (which was non-mycorrhizal) were infected with VA fungi (Daft and Nicolson, 1974).
The harsh procedures used to remove bitumen from sand mined in northern Alberta resulted in mine tailings that are completely devoid of mycorrhizal inoculum (Parkinson, 1979). Zak and Parkinson (1982)found that less than 1% of slender wheat-grass roots grown in untreated sand were infected after one growing season, whereas tailings amended with peat from a forested site resulted in 23% infection.
Lambert and Cole (1979) found the significant effect of pH and a kind of mine waste on VA mycorrhizal yield, when they studied five different vegetated mine wastes and a forest soil as inoculum for white clover in the greenhouse with the spoil adjusted to either pH 4.5 or 6.5. Although VA mycorrhizal infection rates were similar among the inoculation treatments, yield response varied four times at pH 4.5 and fivefold at pH 6.5 with different inocula.
Some mine wastes may contain high levels of potentially toxic metals. On the basis of pot experiments with adding copper and zinc to pots containing a clay loam soil and seeding with clover inoculated with either an isolate of Glomus mosseae from metal contaminated soil or an isolate from an agricultural soil, Gildon and Tinker (1981)have shown that VA mycorrhizal symbionts can become adapted to metal contaminated soils. They concluded that endophytetolerance was important, implying that the mycorrhizal symbionts must be considered as a component of whole plant tolerance to potentially toxic metals.
In field crops and horticultural plants, growth stimulatory influence of VAM-fungi inoculants is well known. Effectiveness of these inoculants has not been clearly demonstrated in forest species except in Liriodendron tulipifera, Agathus australis and Araucaria species. VAM fungi infected plants, when grown in nutrient deficient soils, often produce greater dry weight than not infected plants. Significant enhancement in growth and dry weight of seedlings (Fraxinus americina) inoculated with Glomus epigaeum has been found even at low levels of root colonization. VAM fungi inoculation of Glomus etunicatum can successfully be introduced for producing seedling of Leucaena leaucocephala under low fertility levels. Growth and nutrient uptake by Sesbania grandiflora was improved when sterile soil was inoculated with Glomus fassiculatum and to lesser extent by G. mosseae. Due to VAM fungi inoculation, significant enhancement in growth and survival of several other forest species, e.g. of cuttings of Salix dasyalados and S. daphnoides or flowering dog wood (Comus florida L.) seedlings.
Growing information has been available concerning selection of Rhizobium strains and leguminous plants adopted for planting on mine wastes. The comparative efficiency of different legume species in building up nitrogen contents and increasing growth in a companion grass on mine wastes has been investigated. Introduction of free-living nitrogen fixing bacteria in the rhizosphere of revegetated perennial grass species on strip-mined land has been advocated. Many leguminous and non-leguminous plant species have been tried on coal and dolomite mine overburdens and bauxitemined out areas in Madhya Pradesh in India. The best performance was observed in the case of Eucalyptus tereticornis on coal mine overburdens. However, leguminous plants such as Dalbergia sissoo, Albizzia procera, A. lebbek, Acacia auriculiformis and Acacia meliferia are reported doing better then many non-leguminous plants (Dadhwal et al., 1995; Singh et al., 1995; Nikhil, 1999). At opencast mining sites, the nitrogen fixing trees (NFT) adapt to heavily disturbed soil system and at the same time grow faster to produce heavy foliage to cover the exposed sites.
Biofertilizers being a low cost technology may be advantageously used in wasteland development. Higher monetary return can be achieved with low expenditure as the inoculation cost comes to about Rs. 15–30/ha (Rs. 50 ≈ US $1) by use of various inoculants marketed in India. In less productive soils where the plants are under stress in early growth period, application of 10–20 kg chemical nitrogen per hectare is required for initial growth and establishment of seedlings. Rhizobia can fix up to 80–100 kg nitrogen per hectare, equivalent to 90 kg of urea at just 40% of its cost. Findings from several field experiments revealed that less than a kilogram of high quality rhizobial inoculant, properly placed with legume seeds can replace more than 100 kg of nitrogenous fertilizers per hectare. Economically, the cost of application of Rhizobium culture comes out to be Rs. 0.30 per plant whereas equivalent dose of urea application is to cost about Rs. 2 per plant. Azotobacter culture inoculation can add 30–40 kg nitrogen per hectare per year. Several studies have demonstrated that the biofertilizer use (Rhizobium, Azotobacter, VA mycorrhizae) may provide a valuable and practical tool for achieving the desired end point of reclamation practices on mine wastes.
Here, an over decade's long experience with large-scale implementation in India of mine waste bioreclamation using the integrated biotechnological approach (IBA) has been discussed.
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