Next Generation Growing (NGG) is a set of environmental control techniques for greenhouse or glasshouse cultivation, developed in the Netherlands over the past decade.

NGG aims to achieve two goals. The first is to improve plant growth by improving conditions for photosynthesis and enhancing plant health. The second is to minimize the cost of growing, through the reduction of energy and heat consumption.

The principles of Next Generation Growing can be broken down into 7 easily understood guidelines, to improve production immediately:

  1. Climate Uniformity

Creating even climate conditions in the greenhouse is the most fundamental aspect of NGG. Climate uniformity allows the plants to grow and produce evenly.

Additionally, the environment may be more efficiently controlled as one unit, as opposed to treating problematic spots individually. In this fashion, a homogenous environment provides better conditions for the plants, while reducing management costs and efforts.

More information on achieving climate uniformity

  1. Maintaining an Active Climate

Climate conditions, in general, have a massive effect on the plants’ nutrient transport. Air movement in particular is crucial for stimulating the uptake of water, and subsequently necessary nutrients such as calcium, allowing growth.

This used to be achieved through pipe heating and screen gapping, practices which NGG aims to reduce. The modern glasshouse is much more insulated, allowing thermal screens to be closed for longer periods, drastically reducing the necessary heating.

In order to compensate for the lack of air movement under closed screens, NGG requires air flow to be implemented artificially, with the use of fans or air circulating equipment.

More information on air circulation

  1. Improving Humidity Control

The effects of humidity in a greenhouse are often misunderstood, leading to diseases, suboptimal plant growth and excessive energy consumption.

Next Generation Growing relies on a better grasp of humidity. How it is measured and how it is controlled. NGG consultants advise growers to collect and analyze data regarding humidity. This may be done through several different measurement concepts – relative humidity, absolute humidity and humidity deficit.

In the past, humidity was controlled through heating and ventilating, as well as screen gapping. These methods are extremely inefficient in their use of energy and make it difficult to achieve uniformity in climate conditions.

6 Tips to Increase Energy Efficiency in a Greenhouse

Effective humidity control, using dedicated dehumidifiers, such as DryGair, accomplishes several goals. The reduction of humidity assists in avoiding the dew point, thereby avoiding condensation, which is the major culprit for fungal diseases.

Maintaining optimal levels of relative humidity also increases stimulation of the plants’ stomata, affecting nutrient uptake, as well as photosynthesis.

In addition to plant health and growth, efficiently controlling humidity with dehumidification reduces the need for heating and ventilating, which require more energy and resources to effectively limit humidity levels.

Get a better understanding of humidity in the greenhouse

  1. Dual-Side Above Screen Ventilation

Conventional ventilation practices for greenhouses and glasshouses usually focus on leeside ventilation, in order to reduce temperatures or remove excess humidity. However, NGG focuses ventilating efforts above the screen, as opposed to below the screen. This allows for more effective ventilation with less interference of climate uniformity.

When ventilating above the screen, leeside only ventilation may not be sufficient. It is therefore advised to utilize wind side vents as well, creating greater air movement above the screen, increasing the rate of heat and water transfer with the outdoors.

Generally speaking, larger vent openings create less resistance between outdoor and indoor conditions, translating to greater variation in climate uniformity. Utilizing wind side vents, as well as leeside, allows much smaller openings to achieve the same temperature and humidity reduction, thus reducing climate variance. Dual side ventilation was even found to increase CO2 presence, by reducing its loss to the outside.

Are Thermal Screens Necessary?

  1. Controlling Radiative Heat Loss

 

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During the night, plants release heat to the air. This is called OLR – outgoing long-wave radiation, a type of thermal radiation, emitted from earth’s surface to space. These thermal radiation waves, once met with the cold ceiling, are essentially lost to the sky, causing the top of the glasshouse to cool down rapidly.

Colder head temperatures lead to reduced, or even a complete halt in transpiration, which in turn reduces the rate of nutrient uptake, inhibiting plant growth. Additionally, colder temperatures mean higher relative humidity levels, increasing the risk of condensation and disease outbreak.

For these reasons, NGG experts advise closing the thermal screen during the night, in order to minimize the heat transfer with the outdoors and maintain optimal climate conditions inside the growing space.

  1. Maximizing Photosynthesis

Photosynthesis is the plant’s form of energy absorption and respiration, if it is not able to perform this act, it will cease to grow and will eventually die.

Photosynthesis relies on three basic conditions: light intensity, temperature and CO2 presence. In order to optimize the process, all necessary conditions must be in optimal range.

There are several actions which may be taken in order to maximize photosynthesis in a greenhouse. Reducing ventilation will increase CO2 levels, as it is not lost to the outdoors. Less ventilation also assists in maintaining correct temperatures, as temperatures outdoors vary widely and change rapidly throughout the day. Avoiding water stress is also crucial for photosynthesis. If the air is too dry, stomata will close, as to not dry out, thus directly decreasing photosynthesis.

  1. Balancing Plant Growth

Effective Next Generation Growing involves balancing the plant’s generative and vegetative growth. Vegetative growth refers to the production of leaves and stems, while generative growth focuses on the fruit, flowers and seeds.

In order to maintain growth balance, it is important to maintain a balance between the different environmental factors – temperature, CO2, light and water, so that the plants enjoy the most favorable conditions. An important, often discussed balance, is that between the average day temperature and daily light integral (the amount of light delivered over 24-hour period). The daily light integral is what drives photosynthesis. It is recommended, that when the daily light integral is high, the daily temperature average should be higher as well, and vice versa.

Maintaining the correct balances will ensure optimal photosynthesis, allowing the plant to maximize its potential and decrease susceptibility.

Modern technologies allow growers to base their actions on real time data and relatively accurate forecasts, increasing the ability to properly maintain the correct environment and maximize produce year-round with much greater efficiency. Next Generation Growing takes these advancements and utilizes them to the fullest extent, minimizing inputs, while maximizing outputs.

 

The tips above were originally published as a technical update by GrowSave – “helping horticulture save energy” in September 2018.