4 Uses of Compost in Agriculture and Bioremediation – A Review

       Aparna Gunjal

       Department of Microbiology, Dr. D.Y. Patil, Arts, Commerce and Science College, Pimpri, Pune, Maharashtra

      4.1 Introduction

      Landfill and incineration are the ways of solid waste treatment globally. Methane is the greenhouse gas that causes global warming and that needs to be minimized. Therefore, recycling wastes and organic material by returning to agricultural land is most effective. Composting is the most economical and effective way of recycling by placing organic material back in the soil to enhance soil properties (Awasthi et al. 2014). Landfill of biodegradable waste contributes to environmental degradation due to the production of methane gas (Hurrell 2015). A considerable amount of biodegradable organic waste is generated in most countries, and their management is problematic. Recycling wastes and organic material by returning to agricultural land is essential. Composting is the most cost-effective and promising method of treating wastes. Composting is a biological process that turns organic matter into a dark, rich, colored substance, termed “compost,” which is used as a good soil conditioner. Microbes convert complex organic substances into simpler substances during the composting process with the production of carbon dioxide, water, and minerals and stabilized organic matter called compost. During the composting process, heat is generated that kills pathogens, weeds, etc.

Among waste-management strategies, the composting approach has become very popular in the disposal and treatment of organic wastes with many economic and environmental benefits, including the formation of a stabilized product (Varma and Kalamdhad 2014). The global compost market is studied to reach $9.2 billion by 2024, with a compound annual growth rate (CGAR) of about 6.8% from 2019 to 2024 (www.globenewswire.com). The main aim of this chapter is to highlight the various applications of compost, how it improves the soil’s physico-chemical parameters and boosts plant growth and yield, and how it ultimately benefits farmers. Amendment to the soil to help plant growth is essential. It is therefore necessary to study how compost amends the soil and helps improve agriculture and horticulture.

      4.2 Applications of Compost

      4.2.1 Compost Use for Soil Amendment and as Conditioner

      The role of organic amendments in agriculture is to provide minerals to the crops and improve soil properties. Many physicochemical changes in the soil are due to modifications that help minimize chemical fertilizers (Bonilla et al. 2012). Organic amendments include manure, crop and food residues, compost, and fertilizers. The compost helps maintain soil stability. This also promotes the balance within the agroecosystem. The composting process converts organic waste into a humus-like substance called compost, which can be used as a soil fertility booster (Li et al. 2013).

      Compost helps improve soil properties by minimizing bulk density and enhancing the permeability and stability of the soil. As a result, it also increases the water absorption capacity of the soil (Adugna 2016) and reduces soil abrasion (Martinez-Blanco et al. 2013). Compost improves drought resistance and soil physical properties (Adugna 2016), increases the availability of nutrients and microbial populations, and enhances crop yield (Chelah et al. 2011). Compost use in soil amendment increases surface water infiltration and reduces the intensity of surface run-off from land, and also reduces transport of dissolved and suspended phosphorus and nitrate–nitrogen. The addition of compost in agricultural soil is also known to significantly increase the organic material in the soil (Bellamy et al. 2005).

      Compost amendment to soil also helps delay surface degradation. Tong et al. (2018) have reported the reuse of wastes as compost for enhancing soil properties in the afforested land of Beijing plain.

      4.2.2 Compost to Alleviate Soil Compaction

      Soil compaction is a severe landscape management problem, as it slows turf establishment by stopping the movement of air, water, and minerals within the soil. The standard methods to alleviate soil compaction are costly and require human resources. Therefore, turf managers have been recommending the use of compost and compost mixed with bulking agents. The use of compost and compost with bulking agents helps in root penetration, and turf establishment enhances water-holding capacity and resistance to insects and pests.

      4.2.3 Control of Erosion by the Addition of Compost

Soils that are rich in silt, with low clay deposits, and organic material, erode fast. Compost helps to decrease soil erodibility. The coarseness of the particles in the compost reduces flow velocity. Coarse particles are heavier and do not erode easily. Compost also helps in the establishment of rapid vegetation, and this slows surface flow velocity. Compost-amended soils have reduced erosion by several orders of magnitude over untreated soils (Anastasi et al. 2005). Mulch from wood residual reduced erosion when compared with the control. Hydro compost (consisting of three parts dairy manure compost and one part recycled paper mulch tackifier and water) helps lower soil erosion rates. It increases the seed germination percentage compared with mat fiber mulch with guar tackifier. Compost also plays a vital role in reducing surface and subsurface run-off from the land (Taiwo 2011).

      Goldstein (2002) suggested that soils amended with compost have indicated delays in surface degradation and decreases in sediment run-off.

      On steep embankments of roads and highways, compost is used to reduce soil erosion and establish turf, as compost forms a thick permanent growth to improve soil infrastructure. Turfgrasses are challenging to maintain and sensitive to turf diseases, pests, insects, and soil compaction. Turf managers were using chemical fertilizers, pesticides, fungicides, etc. or a combination of all three, which are rather harmful to the environment. However, turf managers now prefer to use compost for the remediation of turfgrasses.

      4.2.4 Bioremediation of Organic Contaminants, Heavy Metals, and Pesticides in Soils

      Soils are contaminated with harmful chemicals. Potential bioapproaches are biostimulation, i.e., fertilizers and bioaugmentation by adding organic amendments with active microorganisms in it, or the compost. Recently, compost has been used for soil bioremediation. Compost addition can comprise “super bioaugmentation” with a mixture of degrading microbes, combined with “biostimulation” (Kastner