Optimum Interaction between Soil Water Regime and Soil Warming for Convenient Plant Growth Conditions

 
         ABSOLUTE increase in soil moisture and warming should not be considered as optimum environmental conditions for plant growth. Detection of optimum interaction between soil heat and moisture regime as successful practice for plant growth was the main objective of the present study. A field experiment was conducted in three unheated plastic greenhouses, in which black plastic sheet was used parallel to bare soil. Cucumber (Cucumis sativvs) was cultivated and irrigated with micro drip system to achieve three different moisture regimes: greenhouse no. 1 was always brought back to full soil field capacity, FC, while greenhouses no. 2 and 3 were brought back to two thirds and one third of soil FC, respectively. Sensors of digital thermocouple were used to measure soil temperature inserted in: 10, 20 and 30 cm soil depth associated with soil moisture contents. Statistical analysis indicated that, crop yield and some growth parameters were significantly affected by the different irrigation treatments. This finding was considered as basis for decision-making to detect the most appropriate interaction between irrigation and soil warming. The results showed that, the highest moisture contents were recorded at 20 cm depth under mulched soils compared to the upper and lower depths. Also, the lowest values of moisture fluctuation were found under all mulched soils compared to the bare, and were inversely related to both crop yield and growth parameters. High soil temperature (in the upper 20 cm soil layer) interacted with high moisture content was also proportional to crop yield, root depth and plant height in similar manner found with soil moisture fluctuation. Soil heat flux was increased under mulched soil and compared to heat storage, it can be a good indicator for soil warming, and temperature fluctuation, so, it somewhat agreed with moisture fluctuations. Based on observed moisture and soil temperature at different depths of bare soil treatments, it was expected that HYDRUISD-ID code could be used to predict the diurnal pattern of soil water dynamic. Regarding to suitable soil temperature for root growth, results showed that, optimum values were recorded in the uppermost 20 cm of mulched soil under greenhouses no. 1, 3 and associated with suitable plant growth.