Effects of Different Root Zone Heating Methods on the Growth and Photosynthetic Characteristics of Cucumber

Root zone heating can solve the problems associated with the yield and decline in the quality caused by low-temperature stress in cucumber during winter and early spring. An experiment was performed to investigate the effects of different heating methods on the root zone temperature, growth and photosynthetic characteristics, fruit quality, and yield of cucumber. Using traditional soil cultivation (CK1) and sand cultivation (CK2) in a greenhouse as the controls, four heating treatments were set up: soil-ridge sand-embedded cultivation (T1), water-heated soil cultivation (T2), water-heated sand cultivation (T3), and water-curtain and floor-heating cultivation (T4). The results indicated that heating treatments T2 and T4 had better warming and insulation effects than the other treatments during both day and night, with an average temperature increase throughout the day of 0.8–1.2 °C compared with CK1. The chlorophyll content of leaves under the T2 and T4 treatments increased, and the photosynthetic rate and the overall plant growth were significantly higher than in the other treatments. Compared with the control, the fruit yield increased most significantly under the T2 and T4; the soluble sugar, soluble solids, and Vc contents in the fruit increased; while the nitrate content in the fruit decreased, effectively improving the fruit’s quality and yield. It was finally determined that the T2 and T4 heating treatments are the most effective in solving the low-temperature problem. Moreover, as T2 consumed relatively more electricity, the use of a water-curtain and floor-heating system in winter and spring should be considered in order to boost the yield and improve the quality.