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Optimum cool root zone temperature positively influences the production of greenhouse vegetables grown during summer/high temperature period under hydroponics system. Hence, the effect of root-zone temperature was investigated on the growth, yield and nutrient uptake of cucumber (Cucumis sativus L.) plants grown in pots filled with perlite medium under recirculating hydroponic system in greenhouse during summer period (June-August) in two consecutive years 2016/2017 and 2017/2018 using three cooling treatments-T1 (22 ºC), T2 (25 ºC) and T3 (28 ºC) and non-cooled treatment T4 (33 ºC) as control in Randomized Complete Design (RCD). All the treatments received the same nutrient concentrations. Significant (p < 0.05) differences were observed for all the characters viz. plant height, leaf number/m2, chlorophyll content, leaf area (cm2), fruit number /m2, yield (t/gh), fresh (g) and dry matter weight (g) of shoot and root at all cooled root-zone temperatures as compared to control in both the years. Plants at cooled root-zone temperature (RZT) of 22 ºC gave high number of fruits/m2 to the extent of 180 in 2016/2017 and 220 in 2017/2018 followed by that at 25 ºC (167, 221) and 28 ºC (178, 143) as compared to those in control (33 ºC) (101,133) in both the years. Similarly, highest fruit yields were found at cooled RZT of 22 ºC (5.0 t/gh) and 28 ºC (4.7 t/gh) in the first year and 22 ºC (6.1 t/gh) and 25 ºC (6.0 t/gh) in the second year. The plants at cooled RZT responded positively and significantly (p < 0.05) in the uptake of all nutrient elements in shoots and roots in comparison with those at non-cooled RZT in both years.

A 2-year rotation of winter wheat (Triticum aestivum L.)-summer fallow is a dominant cropping system in the dryland region of the Pacific Northwest United States. Traditional, tillage-based summer fallow relies on a soil mulch to disrupt capillary continuity to conserve seed-zone water for early establishment of winter wheat. However, tillage to create the soil mulch and to subsequently fertilize and control weeds often results in unacceptable levels of wind erosion due to the burial of crop residues and the exposure of fine soil particles. Chemical (no-till) fallow (CF) and reduced-tillage fallow (RT) are two alternatives for reducing wind erosion. Our objectives were: (i) to assess the effects of CF and RT on seed-and root-zone temperature and water regimes; and (ii) to test the Simultaneous Heat and Water (SHAW) model for simulating management effects on soil temperature and water. Weather data, soil temperature, and water content were monitored in paired CF and RT treatments during April 2003-March 2004. The RT treatment was observed to retain more seed-zone water over summer compared to CF, consistent with relevant literature for Mediterranean environments and of critical importance to farmers. During the wet winter, CF gained more water than RT because of later planting of winter wheat, and thus less water use. Observed soil temperatures were higher in the CF due to its lower dry soil albedo, higher bulk density and thermal diffusivity than in the RT. SHAW-simulated water contents followed the general trend of the field data, though it slightly under-predicted soil water content for CF and over-predicted for RT. SHAW under-predicted soil temperature during the dry summer and over-predicted for the wet (November-December) period yet the overall trend was properly described with differences between simulations and observations decreasing with soil depth. Overall, SHAW proved adequate in simulating seed-zone and whole-profile soil water and temperature, and therefore may serve as a useful modeling tool for tillage and residue management.

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