Use of Organic Substrates in Sustainable Horticulture
Adnan Younis, M. Ahsan, Ahsan Akram, Ki‐Byung Lim, Faisal Zulfiqar, Usman Tariq
Abstract
The optimum selection of potting mix is one of the most important factors for quality potted plant production as it holds up plant roots, maintains the plant growth and allows free water and air movement to the plant root zone. Under field conditions, due to economic limitations, it is challenging and rather impossible to ensure the desired characteristics of the soil, but in container-grown plants it is feasible to provide the potting mix with desired properties for optimum growth. Optimal potting mix characteristics comprise porosity and density of the medium to facilitate good aeration and water-holding capacity; also, optimum pH and cation exchange capacity synchronize nutrient uptake and absorption, enabling vigorous growth of the plants. This chapter discusses the effect of different organic potting media like sphagnum peat moss, peat moss, shredded bark, leaf compost, coir (shredded coconut husk), farmyard manure, rice/peanut hulls, composted cotton gin waste, spent mushroom compost, agricultural by-products, municipal compost, sawdust, etc., on the growth and development of potted plants. Physical and chemical properties of the medium play a vital role in the availability of food and nutrition to plants. Various physical and chemical properties such as texture, particle size, structure, pore spaces, water-holding capacity, pH, cation exchange capacity, N, P and K percentage of various potting media are reported in this chapter. An inventory regarding various organic materials suitable as a growing substrate for container-grown plants is well-elaborated. Also, the effect of different organic potting media on growth and the morphological characteristics of different ornamental plants are described. Utilization of low-cost renewable materials as growing potting mixes is a significant strategy for sustainable potted plant and seedling production. The nutrient availability is critical when using organic materials as a growing potting mix. Generally, the mineralized nitrogen is present in small quantity in various composts because of the immobilization process and nitrogen loss due to leaching. However, management of composting process and utilizing combination ingredients from different sources can facilitate increased availability of mineralized nitrogen and other essential elements required for optimal plant growth.