The Low-tech Yet High Performance, Off-grid Chinese Greenhouse

The protected vegetable production in China had a share of less than 20% of the total 20 million hectare for vegetables, thus producing 40% of the total vegetables or 60% of the total value. While the traditional greenhouse has seen its steady growth, almost 10% each year, the widely employed season extension facilities have been low-tech plasticulture systems such as solar greenhouse, high/low tunnels, and plastic mulch. The solar plastic greenhouse, or Chinese Solar Greenhouse, has played a key role in winter production of vegetables. Developed in 1989 in Shandong, the largest vegetable production province, this passive solar greenhouse is able to produce warm season vegetables, small fruits, and tree fruits in winter without supplemental heating. The structure of greenhouse consists of three thick, solid walls (north, west and east side), and a “roof’ connected to the north wall. The rest of structure is covered with plastic films. At night, an insulation blanket, which rests on the roof during daytime, will be released to cover the plastic film for added protection from low temperatures. The Chinese Solar Greenhouse was initially made with soil (walls), bamboo sticks (supporting columns), galvanized wires (network to support plastic films and blankets), and straws (blankets). Later, improved designs feature wider span (from 7 to 10m), increased height (from 2 to 4m), reduced number of supporting columns (only one row at the back to support the roof), steel structure, lighter thermal blankets, automated blanket rolling-up/down system, and improved ventilations. The key practices developed include disease resistant cultivars that are tolerant to low temperature and light, vegetable grafting for soil-borne disease resistance and abiotic stress tolerance, trellising and pruning, and CO₂ enrichment. The crop choices and disadvantages of Chinese Solar Greenhouse, and its possible adaptation among small farmers in the United States will be discussed.