Environmental Control of Greenhouse

A greenhouse is a protected structure where crops are grown under controlled environmental conditions to achieve:

Ø Higher yield

Ø Better quality

Ø Year-round production

Ø Protection from adverse weather

Environmental control involves monitoring and regulating internal climatic conditions to keep plants within their optimal growth zone. Environmental control of a greenhouse refers to the systematic regulation of internal climatic conditions to create an optimal Microenvironment for plant growth throughout the crop cycle. Unlike open-field cultivation, a greenhouse or Hitech farming allows partial or complete isolation from external weather fluctuations, enabling precise control over temperature, humidity, light, carbon dioxide concentration, and root-zone conditions. This controlled environment improves crop productivity, quality, and consistency while enabling year-round cultivation irrespective of seasonal limitations. Environmental control is therefore a fundamental component of modern protected cultivation and sustainable agriculture.

Why Environmental Control is Required?

Plants are highly sensitive to their surrounding environment. Any deviation can lead to:

Ø Reduced photosynthesis

Ø Poor flowering and fruit set

Ø Disease and pest incidence

Ø Yield loss

Plants respond directly to their surrounding environment, and even small deviations from optimal conditions can significantly affect photosynthesis, transpiration, respiration, flowering, and fruit development. In uncontrolled conditions, extreme temperatures, low humidity, excessive moisture, or inadequate light can cause physiological stress, increased disease incidence, and yield reduction. Environmental control ensures that plants remain within their optimal growth range, reduces abiotic stress, enhances water and nutrient use efficiency, and enables predictable crop performance, which is essential for commercial greenhouse operations.

Controlled environment ensures:

Ø Stable microclimate

Ø Efficient water and nutrient use

Ø Improved energy efficiency

MAJOR ENVIRONMENTAL PARAMETERS IN A GREENHOUSE

1.     TEMPERATURE CONTROL

Temperature is the most critical environmental factor influencing plant metabolic processes, including enzyme activity, respiration rate, and photosynthesis. Excessively high temperatures can result in wilting, reduced pollen viability, and heat stress, whereas low temperatures slow growth and delay flowering. In greenhouses, temperature is controlled using natural ventilation, exhaust fans, evaporative cooling systems such as fan-and-pad or fogging, and heating devices, such as electric or hot-air heaters. Maintaining an appropriate day–night (diurnal) temperature difference ensures healthy plant growth, improved yield, and better crop quality.

Importance: Influences germination, growth, respiration, flowering and fruiting.

·        Too high → plant stress

·        Too low → slow growth

·        Ideal Range (general crops), Day: 25–35°C, Night: 18–25°C

Control Methods

v Natural Ventilation: Roof and side vents

v Forced Ventilation: Exhaust fans

v Cooling Systems:

v Fan & pad cooling

v Fogging and misting

v Heating Systems:

v Electric heaters

v Hot air blowers

v Hot water pipes

2.      HUMIDITY CONTROL

Humidity plays a vital role in regulating plant transpiration and nutrient uptake. High relative humidity restricts transpiration, leading to nutrient deficiencies and promoting fungal diseases such as powdery mildew and botrytis. Conversely, very low humidity increases water loss from leaves, causing wilting and physiological stress. Greenhouse humidity is managed through ventilation, fogging or misting systems, dehumidifiers, and proper irrigation scheduling. Maintaining relative humidity within an optimal range ensures balanced transpiration and minimizes disease pressure.

Importance: Affects transpiration and nutrient uptake

Ø High RH → fungal diseases

Ø Low RH → excessive water loss

Ø Ideal Range: Relative Humidity (RH): 40–70%

Control Methods

·        Foggers / misters

·        Ventilation

·        Dehumidifiers

·        Proper irrigation scheduling

3.      LIGHT CONTROL

Light is the primary source of energy for photosynthesis and directly affects plant growth, flowering, and fruiting behaviour. The intensity, duration, and spectral quality of light collectively determine plant development. In greenhouses, excessive light can raise leaf temperatures and stress plants, while insufficient light can reduce photosynthetic activity and yield. Light control is achieved using shading nets, whitewash coatings, artificial grow lights (such as LED systems), and photoperiod regulation. Proper light management ensures efficient energy utilization and uniform crop growth.

Importance: Drives photosynthesis, affects flowering and fruiting

Key Light Parameters: Intensity, Duration (Photoperiod), Quality (spectrum)

Control Methods

Ø Shading nets

Ø Whitewash or shade paint

Ø LED grow lights (red, blue spectrum)

Ø Artificial photoperiod control

4.      CARBON DIOXIDE (CO₂) CONTROL

Carbon dioxide is an essential raw material for photosynthesis, and its concentration in greenhouses often falls below ambient levels due to plant uptake, especially in closed structures. Low CO₂ concentration limits photosynthetic efficiency and reduces crop yield. CO₂ enrichment is therefore practiced in controlled environments to maintain optimal concentrations, typically higher than outdoor air. This is achieved using CO₂ cylinders, combustion-based generators, or controlled ventilation. Proper CO₂ management significantly enhances photosynthesis, biomass accumulation, and crop productivity.

Importance: CO₂ is essential for photosynthesis, Low CO₂ reduces plant growth

Optimum Concentration: Normal air: ~400 ppm

Greenhouse optimum: 800–1000 ppm

Control Methods

CO₂ cylinders

Combustion heaters

Proper air circulation

5.     SOIL / ROOT ZONE CONTROL

The root-zone environment directly affects water uptake, nutrient absorption, and overall plant health. Factors such as soil moisture, temperature, aeration, and nutrient concentration must be carefully controlled to avoid root stress. Excess moisture leads to root rot, while moisture deficiency causes drought stress. Greenhouses commonly use drip irrigation and fertigation systems to supply precise amounts of water and nutrients. Substrate-based cultivation systems like cocopeat further enhance root-zone control by improving aeration and moisture retention.

Parameters Controlled:

Ø Soil moisture

Ø Root zone temperature

Ø Nutrient concentration

Ø Control Methods

Ø Drip irrigation

Ø Fertigation systems

Ø Mulching

Ø Substrate-based cultivation (cocopeat)

 Sensors Used in Environmental Control

Sensors provide real-time data for automation. Sensors serve as the backbone of greenhouse environmental monitoring by continuously measuring climatic parameters such as temperature, humidity, light intensity, CO₂ concentration, and soil moisture. These sensors convert physical conditions into electrical signals that can be processed by controllers or IoT systems. Accurate sensor data enables real-time monitoring and precise control actions, reducing human intervention and improving reliability. Proper sensor placement and calibration are essential to ensure accurate environmental representation.

 Actuators Used in Greenhouse Control

Actuators are mechanical or electrical devices that execute control actions based on sensor inputs or controller decisions. Common actuators include exhaust fans, heaters, fogging pumps, irrigation motors, solenoid valves, and artificial lighting systems. When environmental parameters exceed or fall below predefined limits, actuators respond automatically to restore optimal conditions. The coordinated operation of actuators ensures stable environmental control and efficient energy usage.

·        Exhaust fans

·        Heaters

·        Foggers / misting pumps

·        Water pumps

·        Solenoid valves

·        LED grow lights

Manual vs Automatic Control

Manual environmental control relies on human judgment and physical operation of greenhouse equipment, making it labour-intensive, less accurate, and prone to delays. Automatic control systems use sensors, controllers, and actuators to continuously and precisely maintain environmental conditions. Automated greenhouses offer higher accuracy, better energy efficiency, reduced labour requirements, and improved crop consistency. Although the initial investment is higher, automatic control systems provide long-term economic and operational benefits.

       Smart Environmental Control (Modern Greenhouse)

Modern greenhouses increasingly adopt smart environmental control systems that integrate IoT, cloud computing, and artificial intelligence. These systems enable real-time data visualization, remote monitoring, predictive climate control, and intelligent decision-making. Advanced algorithms can forecast environmental changes and adjust control strategies proactively, leading to optimized energy consumption and higher sustainability. Smart greenhouses represent the future of precision agriculture and climate-resilient food production.

Features

Ø Sensor-based monitoring

Ø IoT-enabled data logging

Ø Automatic decision-making

Ø AI-based prediction and control

Benefits

Ø Reduced energy cost

Ø Predictive climate control

Ø Increased yield and sustainability

Challenges in Environmental Control

Ø High initial investment

Ø Energy consumption

Ø Sensor calibration issues

Ø System maintenance

Despite its advantages, greenhouse environmental control faces challenges such as high initial installation costs, energy-intensive heating and cooling, sensor reliability issues, and system maintenance. Poor system design or improper calibration can lead to inefficient control and increased operational expenses. Addressing these challenges requires careful system planning, renewable energy integration, and skilled management.

Advantages of Proper Environmental Control

Ø Year-round crop production

Ø Higher productivity

Ø Better crop quality

Ø Reduced pest and disease incidence

Ø Efficient use of water and energy

 Environmental control is the cornerstone of greenhouse technology, enabling precise regulation of climatic and root-zone parameters to optimize plant growth. By integrating controlled temperature, humidity, light, CO₂, and soil conditions with modern automation and smart technologies, greenhouses can achieve sustainable, efficient, and high-productivity agriculture. Proper environmental control transforms traditional farming into a reliable and technologically advanced food production system.