Energy-saving greenhouse construction and management

Author: Chief Editor: Chen You
Publisher:
Publishing Date: 2003-06-01
Features: Preface Since the Third Plenary Session of the Eleventh Central Committee of the Communist Party of China, under the guidance of Deng Xiaoping's theory of building socialism with Chinese characteristics, China has implemented a series of reform and opening-up policies in rural areas, leading to significant changes in the rural landscape. However, the potential for rural development in China remains substantial. To achieve rapid economic growth in rural areas, enrich the nation, and revitalize the Chinese nation, it is urgently necessary to rely on science and technology to revitalize agriculture and the rural economy. To this end, China Agricultural Press organized and edited personnel to conduct extensive, multi-level field investigations in rural areas. Based on the needs of farmers, hundreds of experts with high theoretical levels and rich production experience were invited to compile this large-scale series, "The Rural Book Collection of China." It is hoped that the publication of this series will provide guidance for agricultural production, the development of the rural economy, and the improvement of farmers' lives. This series consists of over 100 titles, covering all aspects related to farmers, such as agricultural policies, laws and regulations, ethics, rural economy, planting, animal husbandry, storage and processing of agricultural products, agricultural machinery, and rural healthcare. Considering the current cultural level of farmers in China, this series uses simple and easy-to-understand language and is primarily written in a Q&A format. It emphasizes the connection between theory and practice, clear reasoning, and provides farmers with more knowledge. In terms of agricultural production techniques, it focuses on introducing key production links, technologies, methods, and successful experiences, many of which are research findings from domestic and international studies, as well as high-yield, high-quality, and high-efficiency production techniques with strong operability. The series aims to combine scientific rigor with practicality, enabling farmers to solve problems encountered in production and achieve better results. Sincerely, we hope that rural readers can benefit from this series, achieve poverty alleviation and wealth through hard work, and lead a moderately prosperous life. China Agricultural Press July 1997
Excerpt:
Second, greenhouses should not be built on windward sites to reduce heat loss and wind damage to the structures. If a greenhouse is to be built in a courtyard that is on a windward site, a lean-to greenhouse or cold frame can be constructed, with a windbreak on the south side to minimize wind damage.
Third, avoid sheltered areas. Ventilation channels should be installed first in sheltered locations before building a greenhouse. Otherwise, poor ventilation can lead to severe crop diseases, and excessive snow accumulation in winter can also damage the greenhouse.
Fourth, sandy loam is the best soil for building greenhouses, with clay loam as the subsoil. Such soil types have higher temperatures, which are beneficial for crop root growth. If the soil is too clayey, add an appropriate amount of river sand and apply more organic fertilizer to improve it. If the soil is too alkaline, acidic fertilizer must be applied before building the greenhouse to correct the pH level.
Fifth, greenhouses should not be built on low-lying, waterlogged land. Drainage ditches must be dug first before construction. Additionally, if the groundwater level is too high or the land is prone to frost heave, the site must be elevated with extra soil before building the greenhouse. Otherwise, low soil temperature and excessive moisture will hinder crop root growth.
Sixth, ensure adequate water supply, convenient transportation, and power supply for management and product transportation. Land near industrial enterprises can be utilized to develop greenhouses using industrial waste heat, which helps save energy and reduce production costs. For industrial enterprises that emit toxic gases or harmful wastewater, greenhouses should only be built after the pollution is treated to meet safety standards to develop pollution-free vegetable production.
In summary, building a greenhouse is a project with significant one-time investment. It should not be built blindly or excessively. It must adhere to principles such as using local materials, saving energy, being economical and practical, reducing costs, and maximizing utilization. Choose a suitable site for greenhouse construction based on the above requirements.
(II) Planning the Site for Energy-Saving Greenhouses and Large Greenhouses When building energy-saving greenhouses and large greenhouses on the same plot, a comprehensive plan should be made. If large greenhouse production is the priority, a seedling greenhouse must be equipped. The ratio is that for every 667 square meters (1 mu) of plastic greenhouse used for vegetable production, a seedling greenhouse with an area of 20 square meters must be built. This seedling greenhouse can start growing vegetables in cold seasons earlier for the large greenhouse and other protected areas. To improve the economic benefits of vegetable production, multiple protected area facilities should be constructed in the same location, such as greenhouses, large greenhouses, small greenhouses, cold frames, and plastic mulching.
In specific planning, the following issues should be noted:
(1) Greenhouses used for planting should be built on the north side of the site due to their high height. A large greenhouse should be built in front of the greenhouse, and medium greenhouses should be built on the south or both sides of the large greenhouse. On the south side of the site, cold frames or cold beds (sunny beds) and small greenhouses can be built. This planning, with decreasing height from north to south, not only facilitates operation and management but also prevents shading between structures, effectively utilizing solar energy and land area.
(2) The orientation of greenhouse construction should be east-west, with a southward deviation of 5° to 10°. This orientation ensures good winter sunlight, longer daylight hours, and higher indoor temperatures. If a greenhouse faces due south or is excessively skewed, both winter sunlight and temperature inside the greenhouse will be poor. The orientation of a greenhouse is generally unrelated to its construction cost but is closely related to the quality of the light environment it creates and the overall economic benefits. The orientation of a greenhouse refers to the direction of its roof ridge. A south-facing greenhouse has an east-west orientation. In the past two decades, agricultural building professionals worldwide have conducted extensive research on this topic, focusing on solar radiation entering the greenhouse as the basis for comparison and measurement. This is because solar radiation directly affects the yield and quality of most plant products and, to some extent, influences energy consumption. Currently, energy-saving film greenhouses in China only receive sunlight on the south-facing side, with north-facing and side walls made of non-transparent insulation materials. All are oriented north-south with east-west extensions to maximize sunlight on the south-facing side. Some greenhouses facing north are built for specific needs requiring weak light.