Growth Effect And Sap Flow Of Greenhouse Muskmelon Under Different Irrigation Methods

Water lack is one of the world's serious problems; the development of water-saving agriculture is an important way to solve the problem. As the development of social economic, the quality of vegetable and fruit is more and more important in protected cultivation, in order to meet the demand of modern society, the focus of agricultural research should change from the improvement of quantity to quality. Muskmelon is a kind of wide planted economical crop in China; it is popular for its short development period, high yield and good quality. But furrow irrigation is the main irrigation method in this area, and the time and frequency of irriagion is decided according to the experience, in this condition disease appears frequently. In this paper the effect of irrigation method on the development, yields and water use efficiency was discussed, and the comprehensive benefit was explored, respectively. The feasibility of sap flow technology based on heat balance method was verified, too. The main conclusion was as follows:(1) The plant characteristics such as plant development, quality, yield and water use efficiency showed that 75%θ_fc was the best irrigation lower limit in both indirect subsurface irrigation and mulching irrigation, and the best aeration frequency was once per two days.(2) The develop ratio (DR) of greenhouse muskmelon expressed as growing degree days (GDD) showed that DR was high in ripeing stage, middle in flowering and seedling stage, low in swelling and strawing stage. The variance range was between 0.079 and 0.135 in different development stage and nodes of greenhouse muskmelon leaves, so the leaves area measurement in ruler method was feasible, and the revise coefficient is 0.677.(3) Comprehensive plant characteristics were established according to principle component analysis, and the plant development trend condition could be expressed perfectly using the logistic development equation between comprehensive plant characteristics and available cumulate air temperature. Photosynthesis active radiation using ratio showed that compared with control, twice per day, once per day, once per two days and once per three days treatment can rise 8.929%, 21.296%, 28.649% and 25.466%, respectively. Aeration frequency with once per two days was propitious to improve photosynthesis active radiation using ratio.(4) Comparison between the best irrigation sheme of indirect subsurface irrigation, mulching irrigation and aeration irrigation was conducted, and results showed that aeration irrigation was the best irrigation method to spread because of the improvement of yield, quality and water use efficiency.(5) The mathematical relation research was conducted in path analysis which was established by fruit weight and plant characteristics under plastic mulching drip irrigation and fresh matter weight directly influenced fruit weight significantly. The application of entropy model and principal component analysis model in comprehensive quality evaluation under aeration treatment subsurface drip irrigation showed that those two models had the same conclusion, and the greenhouse muskmelon quality was better under aeration irrigation than normal subsurface irrigation and the quality was the best in once per two days aeration frequency treantment. The comprehensive benefit evaluation of greenhouse muskmelon in multi-layer, multi-objective system fuzzy mathematical method showed that the order was 75%θ_f>85%θ_f>65%θ_f>CK>55%θ_f under indirect subsurface drip irrigation and mulching irrigation, and once per two days>once per three days>twice per day>once per day>control under aeration irrigation, respectively.(6) The sap flow characteristics of greenhouse muskmelon in sap flow method based on heat balance principle is explored, and the sap flow laws in different weather condition was discussed. Correlation analysis and gray correlative degree analysis showed that solar radiation and photosynthesis available radiation affected sap flow density significantly. Multi-linear regression model and BP artificial neural network model were applied to fit sap flow density and environmental factors; results showed that BP artificial neural network model had very high fitting precision. The transpiration in sap flow method was validated in plot weighing mehod; results showed that sap flow mehod was feasible in greenhouse muskmelon transpiration measurement.