Agro-industrial-residues as potting media: physicochemical and biological characters and their influence on plant growth

Biomass Conversion and Biorefinery https://doi.org/10.1007/s13399-021-01998-6 REVIEW ARTICLE Agro‑industrial‑residues as potting media: physicochemical and biological characters and their influence on plant growth Pratibha Agarwal1 · Sampa Saha2 · P. Hariprasad1 Received: 31 May 2021 / Revised: 9 September 2021 / Accepted: 24 September 2021 © The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature 2021 Abstract Nursery cultivation is recognized globally as an intensive production system to support quality seedlings as well as to manage resources efficiently. Apart from other factors, potting media (PM) play a crucial role in determining the success of nursery cultivation. Worldwide, peat is the most commonly used substrate in PM because of its favorable physicochemical properties. However, due to ascending environmental and ecological concerns regarding the use of peat, a variety of new substrates have been used/tested by researchers/practitioners/growers as PM. Bark, coir pith, wood fiber, compost derived from various agro-residues, and vermicompost either alone or in combination are some of the commonly explored substrates and found to have the potential to replace peat to a greater extent. In lieu of availability, abundance, low cost, and no/low processing requirement, the use of agro-industrial residue (AIR) in the PM is the current trend. However, challenges associated with their adoption cannot be ignored. The present review is focused on providing collective information, scientific knowledge and detailed analysis of various AIR used in PM. The critical evidence-based review would help in developing a consistent approach for the identification, selection and characterization of a new renewable substrate. In addition, it would help in developing a rationale understanding of the practical and economic realities involved in the adoption of the same in PM. Keywords Potting media · Paddy straw · Deoiled seed cake · Agro-industrial-residue · Peat · Transplant 1 Introduction Transplant production, especially for vegetable and floriculture, has become popular in the last two decades to enhance resource efficiency as well as to reduce the environmental impact [1]. Early and uniform crop maturity, efficient management of land, energy, time and seed materials, production of pestfree transplants, reduction in pesticide and herbicides usage, and most importantly healthy and homogenous seedlings are some of the advantages of transplant production [2–4]. The profitable opportunities offered by this production system are the reason for the enhanced demand for seedlings, especially for the production of vegetables and flowers. Looking into * P. Hariprasad ; 1 Centre for Rural Development and Technology, Indian Institute of Technology Delhi, Hauz Khas, New Delhi, India 2 Department of Materials Science and Engineering, Indian Institute of Technology Delhi, Hauz Khas, New Delhi, India the advantages of the transplant system, researchers extended their applications into a wide range of plants, including sugarcane and forestry species (pine, beech, spruce, etc.) [5–7]. Ornamental plants production is another emerging horticulture sector in terms of volume, value, specialization, as well as commercialization. Quality, homogeneity, and standardized products is one prerequisite to achieve success in producing ornamentals [8]. Potting media (PM), fertilizers, permitted pesticides, seeds, labor, and the infrastructure itself is the main inputs in greenhouse nurseries and ornamental plant cultivation [1]. After labor, PM is the second prominent contributor to total greenhouse production cost [9]. Two fundamental challenges before soilless cultivation are, (i) unlike a normal soil profile, a pot provides a very shallow layer of a PM that saturates quickly during irrigation; (ii) small pot volume provides limited capacity for water storage between irrigation events [10]. Indeed, an effective PM must have a physical structure that can sustain a favorable balance between air and water content both during and between irrigation events in order to prevent root asphyxia and drought stress [11, 12]. The inability of the 13 Vol.:(0123456789) Biomass Conversion and Biorefinery soil to provide this balance at such small volumes is a key factor in the development of soilless PM. Indeed, these PMs have been a pivotal innovation, allowing growers to ensure rationale supply of water, air, and nutrient to the plant while excluding soil-borne pathogens [13]. Peat is the most widely used substrate in PM [13–15]. However, due to ecological and environmental concerns, the use of peat in PM is under high scrutiny. This had given a thrust to examine a wide range of alternative materials in PM. In spite of exploring a diverse range of new materials, only a few of them have been adopted widely. This review critically examines all the issues and provides an overall and comprehensive knowledge of: (1) all the widely used substrates in PM (2) some new renewable substrates which were not investigated in detail (3) selection and evaluation criteria of an unconventional substrate in PM 2 Background Historically, horticulturalists were using a mixture of composted organic waste and mineral soil for growing plants. Usually, the soil was not sterilized or pasteurized. Consequently, the chances of soil-borne pathogens and insect infestation were very high. Also, these mixtures were usually unbalanced in nutrition with varied physical properties reducing the consistency of PM performance. In the United Kingdom (UK), in 1930s, Lawrence and Newell standardized growing media called “John Innes” (blend of loam, sand, and peat in 7:3:2 ratio, respectively) for commercial purposes [16]. Here, the loam was sterilized to eliminate pathogens and pests. Additionally, necessary nutrients status and desirable physical properties were taken into consideration while developing the media to achieve optimum plant growth. Since loam was the main “body” of this media, its usage was limited by difficulties in transportation and handling because of its heavy weight. During 1950s in the United States (US), due to the widening of greenhouse crop production and containerized nursery, researchers and practitioners identified bark and peat as the most efficient soilless components for PM production. Later, in the 1970s, peat was explored successfully as an alternative to loam to make transportation cost effective [17]. Considering the ease of handling and beneficial properties, with time peat became the major component of PM and still dominates the sector. About 40 million cubic m3 of peat is used annually worldwide in horticultural production [18], among which Germany (8.5 million m3) and UK (2. 5 million m3) are the major consumers of peat in horticulture media [19]. 13 Peatlands are highly fragile ecosystems, which are natural habitats of huge biodiversity. Peatlands contain 15–35% of re (...truncated)