Agricultural Wastes and Its Applications in Plant-Soil Systems
ABSTRACT
Agriculture is the largest sector in the world, which supplies raw material to almost all the industries right from the food industry to textile, construction, mechanical, and energy to even the cosmetics industry. It produces a different type of raw materials for different industries like cereal crops, sugar cane, vegetables, and oil crops for the food industry, cotton for the textile industry, wood for construction and mechanical industries, and different plant products/extracts to make cosmetic products. Besides, the agriculture industry includes crop residues (CR), animal dung, sugarcane bagasse, livestock annual dead bodies, pruning waste, cotton stalk, etc. These wastes can be used for the betterment of soil and plant health, including energy production, by converting them into useful products. These products are produced by some processes like composting, biochar, and manure production. Some other uses of agricultural wastes (AW) include as biosorbents for heavy metals, crop residue supply to soils, mulching, and energy production fr om household to large scales. This chapter discusses the prospects of AW uses for soil and plant health improvement along with future directions.
INTRODUCTION
Agricultural wastes (AW) are unwanted materials formed from agricultural activities and its associated operations. These activities could be the growing of crops or livestock and herd management, and raw material processing in industries produced from agriculture (Zhou et al., 2015). Agricultural waste can also be soil sediments, nutrient, and pesticides runoff from the soil as a result of flooding or rams (Sharifi et al., 2016; Quinteros et al., 2017), different animals wastes (ElMekawy et al., 2015), crop residues (CR) (Quinones et al., 2015), poultry wastes (Abouelenien et al., 2016), dead or slaughtered animals waste (Arshad et al., 2018), vegetables processing waste (Bakatovich et al., 2018) and water containing burned tree and crop ashes resultant of the accidental fire in agricultural fields (Rajput et al., 2016). To manage these AW, a complete understanding of their composition, physical, chemical, and biological reactions is necessary, along with the factors controlling then fates in the environment. Soil application of natural or synthetic chemicals is an important practice which supplies nutrients and improves soil fertility, soil biological and physical properties (Vaisanen et al., 2016). Pyrolysis of AW is also done to achieve waste management, energy production, and biochar formation for soil application (Lee et al., 2017). CR can also be applied as such in the soils and proved an important addition for soil health and crop production (Hatfield, 2017; Gul et al., 2015). Poultry manure (PM) is also used as a nitrogen (N) source and contains up to 1.5 gkgr1 of N, 0.8 g potassium (K), and 0.5 gkg-1 phosphorus (P) (Moshia et al., 2016). The production of composts from AW for soil conditioning is also a sustainable way to manage these wastes and in alleviating salt-affected soils. By using compost, soil microbial activities, microbial C and N, and soil respiration were improved, which showed that the importance of compost (Murphy et al., 2016).
Different AW used as agricultural soil amendments include municipal sewage, agro-industrial, slaughterhouse, AWs compost, AW compost, pig slimy, digestate, and paper mill wastes to improve soil physicochemical properties and control bioavailability of heavy metals and organic contaminants. Application of these AW lowers the bioavailability of contaminants in soil and plants and then use as pollutant removal agents (Alvarenga et al., 2015). Biochars of different CR also proved effective in immobilizing metal soils. Some wastes like cow dung also used as a source of energy through biogas production (El Mekawy et al., 2015; Nandi et al., 2017), biofuel production (Prasad et al., 2017), and also used as a domestic fuel in houses for cooking (Xiao et al., 2015) as well as mulching (Chen et al., 2018). In addition, this chapter also discusses comprehensively the agricultural waste advantages, their effective uses, and its effects on soil and plant health along with the negative impact on soil properties deterioration as a result of CR burning.
TYPE OF AGRICULTURAL WASTES (AWS)
There are many types of AW used in agriculture and of different origin, mostly from crops like wheat, rice, maize, sugarcane, cotton, and millet, from forestry includes tree branches, leaves, and wood, horticulture wastes include thinning and pruning wastes, vegetable leaves, and processing and livestock wastes comprising of animal dung, dead, and slaughtered animals waste and their manures.
FORESTRY WASTE
Agricultural forestry is a big contributor of AW in terms of tree branches, thinning, and pruning of trees for making them tall and big canopy size leaves (Figure 2.1). Tree branches are also broken and fell down as a result of heavy rains and storms. Many temporary and perennial forestry crops and forest residues are generated each year (Nones et al., 2017) from different forest trees like eucalyptus shed leaves and its bark. Some trees shed more leaves in a specific time of the season, and some of their branches to grow taller. Forest biomass and waste degrade, slowly making the forest soils more and more productive. Organic matter is increased in these types of forests, which promotes further plantations and forest growth (James et al., 2019; Santos et al., 2016).
FIGURE 2.1 Forestry waste.
HORTICULTURE WASTE
Horticulture waste includes different crop wastes and by-products after their processing. For example, fruits and vegetables as consumed raw, minimally processed, as well as processed, due to their nutrients and health-promoting compounds. Thus, significant losses and waste in the fresh and processing industries are produced. The United Nations Food and Agriculture Organization (FAO) has estimated that losses and waste in fruits and vegetables are the highest among all types of foods and can reach up to 60%. The processing operations of fruits and vegetables produce significant wastes or by-products, which constitute about 25% to 30% of a whole commodity group. The waste is composed mainly of seed, skin, rind, and pomace (Sagar et al., 2018). In addition to the food crops, different ornamental plants are also a big source of AW as these plants are cut and pruned to modify for making different canopy shapes or heights after pruning (Wu et al., 2016; Roslim et al., 2018).
AGRONOMY WASTE
Major crops used in the food are categorized under the umbrella of agricultural crops or agronomy, including wheat, rice, and maize grown individually or in combination to other staple crops in different parts of the world. Thus, the production being high, these crops produce a huge amount of AW with food grains. When crops are harvested, a huge amount of CR are left behind in the fields (Speratti et al., 2017). Apart from the CR, other AW are com cobs produced after the use of maize grains, cotton stalks after the picking of cotton, and other miscellaneous plant parts. Agronomical wastes also include dead plants, seeds of all kinds, and a mixture of soil runoff, leaching of nutrients, and eroded soil and nutrients (Nanda et al., 2016).
LIVESTOCK WASTE
Livestock production is a rapidly increasing industry, especially in developing countries, due to the increased consumption demands for meat and other daily products. Due to this, larger quantities of animal wastes are leftover (Figure 2.2); these wastes include animal dung, dead, and slaughtered animal waste, animal blood, and different manures like poultry and pig manures (Zhu and Hiltunen, 2016; Zhu et al., 2017).
FIGURE 2.2 Livestock waste.
