Abstract:

It’s so important that the yield and quality of muskmelon plants which are more and more cultivated in the greenhouse would be increased by reasonable irrigation mode and desicition. Based on ascertaining the variation and effect factors of sap flow rate, the index of muskmelon plant moisture capacity were determined by highly effective irrigation decision-making. Dynamax Sap Flow Measuring System, Automatic Weather Station System and TRIME-IPH were used to simultaneously measure and monitor the muskmelon sap flux density, environmental factors and soil water content. Based on the analysis of the diurnal variations of stem sap flow and environmental factors, the results showed that: Diurnal sap flux density had the double peak pattern, the started time of sap flow delayed 1-2 hours on cloudy and rainy days, and the peak value decrease 15%-47%. The muskmelon transpiration velocity was much higher in sunny days than in rainy or cloudy days, and there was day depression of transpiration markedly in midday, and the sap flow also existed at night. There was no depression of transpiration in rainy days, and the sap flow velocity was zero under the condition of highest air relative humidity at night. Solar radiation (Rs) and air relative humidity (Rh) lag behind the sap flux density, but in rainy or cloudy day solar radiation (Rs) and sap flux velocity achieve the peak simultaneously. Solar radiation (Rs) was the most important affecter to the sap flux density in the stage of fruit enlargement, the regression equation was established (F=26.204+0.0890Rs-0.2540Rh, R2=0.831, P<0.001) based on solar radiation (Rs) and air relative humidity (Rh). The tinny increasing of air relative humidity (Rh) in sunny midday which the solar radiation (Rs) laid in the high level made sap flux density decrease.