Introduction to Controlled Environment Horticulture

Stephen Oyedeji1, *
1 Department of Plant Biology, Faculty of Life Sciences, University of Ilorin, Ilorin, Nigeria

Abstract

Controlled environment horticulture (also called protected structure cultivation), the concept of cultivating horticultural crops in protected structures, dates back to 14 AD. This method of cultivation offers protection to crops by regulating environmental factors (both biotic and abiotic factors) as per the crop's requirements while reducing the incidence of pests and diseases. This chapter elucidates the diverse designs of protected structures in controlled environment horticulture, tailored to meet the growth requirements of various or specific crops. The regulations of environmental conditions (such as light, temperature, humidity, ventilation, water, nutrients, and pests) and the mechanisms of achieving optimum growing conditions are also highlighted. The huge initial investment and operational costs of controlled environment horticulture are stressed, and the need for improvement in the various designs is advocated to achieve energy sustainability while reducing costs.

Keywords: Controlled environment, Disease, Humidity, Light, Management, Nutrients, Nutrient pest, Soil, Substrate, Temperature.

* Corresponding author Stephen Oyedeji: Department of Plant Biology, Faculty of Life Sciences, University of Ilorin, Ilorin, Nigeria; E-mail: oyedeji.s@unilorin.edu.ng

INTRODUCTION

The term horticulture is a derivative of the Latin words hortus, meaning 'garden', and cultura, meaning 'cultivation' [1]. Simply put, horticulture is the cultivation of crops in an enclosure, i.e., in a garden. The concept of horticulture as "garden cultivation" is overly simplistic, as it does not present the categories of crops associated with this type of cultivation. In a broader view, horticulture is considered an aspect of agriculture that focuses on the cultivation of plants for flowers, fruits, vegetables, medicines, aroma, and aesthetics (or beauty). [2] A study defined horticulture as the science of cultivating vegetables, herbs, fruits, nuts, and ornamental plants (including turfs, grasses, shrubs, and trees) [3]. Another study considers horticulture to include the art, science, technology, and business of gardening vegetables, fruits, flowers, seeds, and nuts.

According to von Baeyer (2024) [2], horticultural practice dates back to about 20 millennia, when hunters and gatherers embarked on the trial-and-error approach of domesticating wild plants collected from diverse ranges in an attempt to breed the food closer to their shelters. Although agriculture and horticulture could be said to have begun at a time and evolved together, the approaches of these two fields differ considerably in terms of production, specialisation, and commercialization. Modern agriculture is often carried out on large expanses of fields and involves mono-crops in order to adapt cropping to mechanised processes of cultivation, harvesting, and processing. Its main goal is to promote the commercial production of food and food-related items, including livestock. Contrastingly, horticulture includes production that takes place in both open spaces (such as gardens, lawns, and parks) and enclosed areas (such as screen houses and greenhouses) and supports the mixing of varieties of plants (including fruits, vegetables, medicinal, and ornamental plants) in an area or space, as opposed to their seclusion in separate rows or plots. This approach offers great physiological and environmental benefits such as efficient nutrient and moisture utilisation, optimum photon trapping, and exploitation of micro-environmental variation leading to increased photosynthetic efficiency. For example, intercropping legumes (such as purple-hulled peas, garden peas, snap beans, and yard-long beans) with vegetable crops is being promoted in sustainable horticultural practices to reduce reliance on chemical inputs such as fertilisers [4].

Horticulture is an important aspect of the farming system that is aimed at advancing the quality of life of man as well as the beauty, sustainability, and restoration of the ecosystem. These goals are achieved through the production of healthy and nutritious food, promotion of biodiversity, improvement of ecosystem aesthetics, mitigation of climate change through the reduction of carbon footprint, and improvement of air quality and living conditions of organisms. Horticulture deals with a great variety and diversity of plants, thus acting as a major driver for agricultural and economic diversification.

Horticulture is classified on the basis of the major categories of crops it deals with. The major branches of horticulture include pomology, the production of fruit crops, olericulture, the production of vegetable crops, and floriculture, the production of ornamental plants. In recent times, landscaping- the art of enhancing the beauty of the visible features of an area of land through the modification of its terrain, plant arrangements, and the installation of patios, walkways, and other spaces- has become an integral part of horticulture. Landscape gardening is an evolving and aesthetic branch of horticulture that deals with the design of landscapes using ornamental plants in a fashionable way that presents a picturesque.

Controlled Environment Horticulture (CEH) refers to the gardening of specialty crops, including fruits, vegetables, spices, ornamental and aromatic plants, and mushrooms, within protected structures or indoor systems, such as screen houses, greenhouses, vertical farms/plant factories, and other facilities, where advanced technology is employed to control the environmental conditions such as temperature, humidity, lighting, gaseous exchange, pests, and pathogens.

The horticultural practice of cultivating crops in controlled environments, also known as protected cultivation, dates back to ages, with the earliest record around 14 AD in Rome, where cucumber plants (Cucumis sativus L.) were grown in prototype greenhouses (called specularia) constructed for Emperor Tiberius (42 BC-37 AD) presumably beside his palace on the Island of Capri [5, 6]. This was done to evade the cold winter season and get cucumbers year-round for the Emperor. It was on record that there was never a time the gardeners failed to meet the Emperor's demand for the fruit [6]. Protected structures offer protection to crops by regulating environmental factors (both biotic and abiotic factors) as per the crop's requirements. These structures can be used to prevent, delay, or even mitigate pest and disease incidences in crops by modifying the environmental conditions (such as temperature, humidity, and other factors) against pests and pathogens. Controlled environment horticulture thus offers the immense advantage of producing healthier crops with improved yields and quality in stark contrast to traditional gardening or farming, which relies on environmental impulses and can be significantly impacted by extreme conditions like excessive heat, frosts, droughts, and floods. Protected structures are used to regulate conditions of growth by creating perfectly balanced environments that meet the requirements of crops, allowing for all year-round production. Not only does this environmental control ensure consistent production and yield, but it also allows for the cultivation of crops in places that are traditionally unsuitable for them [7].

There are various types of protected structures employed in modern horticulture. These structures can be categorised on the basis of materials used and structure designs. Materials commonly used in the design of protected structures for controlled environment horticulture (CEH) include glass sheets, polycarbonate sheets, plastic films, and polyethylene films and nets (also called HDPE nets-high-density polyethylene nets). Different structures used in controlling environmental factors in horticulture include greenhouses, polyhouses, net houses, raised beds, trellis, and drip irrigation systems. These structures are being used independently or in combination to offer optimum growing conditions and protection against severe weather conditions, pests, and pathogens while allowing for out-of-season or year-round planting [7].

Controlled environment cultivation can be broadly categorised into soil-based and soilless methods. In soil-based cultivation, natural soils or soils supplemented with nutrients are the medium for crop production. This medium provides a base for the root systems and supplies dissolved nutrients in the soil water for the growth of plants. Soil also harbours microbes that play beneficial roles in plant nutrition [8]. Soilless cultivation is any method of growing plants that excludes the use of soil as a rooting medium but involves the supply of nutrients to the roots using irrigation water [9]. Soilless planting can be adapted into hydroponics, aeroponics, aquaponics, and solid media cultures, which are supplied with nutrient-rich solutions to facilitate crop growth.

Cultivation using soil or soilless medium in...