The yield and quality of field crops are affected by abiotic stresses such as water deficit, which can negatively impact crop growth, productivity, and quality. However, nanotechnology holds great promise for increasing crop yield, maintaining quality, and thus mitigating abiotic stresses. Therefore, the current study was conducted to examine the influences of 0, 50, and 100 mg L⁻¹ zinc oxide (ZnO) nanoparticles and 0, 25, and 50 mg L⁻¹ silicon dioxide (SiO₂) nanoparticles on the yield and quality traits of potato plants grown under water deficit conditions (100%, 75%, and 50% ETc). Water deficit significantly reduced yield traits (average tuber weight, number of plant tubers, and tuber yield) and quality traits (tuber diameter, crude protein, and mineral content). However, it enhanced tuber dry weight, specific gravity, ascorbic acid, starch, and total soluble solids. Foliar applications of ZnO and SiO₂ nanoparticles under water deficit treatments significantly enhanced yield and improved quality traits of potato plants. Moreover, significant and positive correlations were found among yield traits. Thus, it can be concluded that using ZnO NPs at 100 mg L⁻¹ significantly improves potato productivity and quality traits by mitigating the negative effects of water deficit in arid regions.

Abiotic stress decreases crop production worldwide. In order to recommend suitable genotypes for cultivation under water deficit and heat stress conditions, an overall understanding of the genetic basis and plant responses to these stresses and their interactions with the environment is required. To achieve these goals, the multitrait genotype-ideotype distance index (MGIDI) was utilized to recognize abiotic-stress-tolerant wheat genotypes, and the weighted average of absolute scores (WAASB) index as well as the superiority index, which enables weighting between the mean performance and stability (WAASBY), were utilized to recognize high-yielding and stable genotypes. Twenty wheat genotypes were examined to determine the abiotic stress tolerance capacity of the investigated genotypes under nine test environments (three seasons × three treatments). Abiotic stress significantly decreased most morpho-physiological and all agronomic traits; however, some abiotic-stress-tolerant genotypes expressed a slight reduction in the measured traits as compared with the control group. G04, G12, G13, and G17 were identified as convenient and stable genotypes using the MGIDI index under all environments. Based on the scores of the genotype index (WAASB), G01, G05, G12, and G17 were selected as superior genotypes with considerable stability in terms of the grain yield (GY). G04, G06, G12, and G18 were classified as cluster (I), the productive and stable genotypes, using the WAASBY superiority index. The combined indices (MGIDI and WAASB) and (MGIDI and WAASBY) revealed genotypes G12 and G17 and genotypes G04 and G12, respectively, as the most stable candidates. Therefore, these are considered novel genetic resources for improving productivity and stabilizing GY in wheat programs under optimal conditions, water deficit, and heat stress. The genotype G12 was jointly expressed in all three indices. Stability measures using WAASB may help breeders with decision-making when selecting genotypes and conducting multi-environment trials. Hence, these methods, if jointly conducted, can serve as a powerful tool to assist breeders in multi-environment trials.

Shading the greenhouses is necessary in summer to reduce the solar radiation load. This however generates a considerable amount of thermal radiation heat load that needs to be removed via cooling systems. This study aimed to evaluate the effect of different shading configurations on the solar and thermal radiation in a greenhouse. Nets at four different locations were employed to shade the roof and side-walls of a polycarbonate, mechanically ventilated greenhouse. The spectral radiative properties of all these plastic materials were measured in short and long wave spectrum bands. The net solar and thermal radiations and air temperature were measured outside and inside two identical shaded and unshaded greenhouses. The results showed that external roof-shading is desirable, as it reduced the generated thermal radiation in the greenhouse by 21% and 15% during the day and night time, respectively and reduced the greenhouse air temperature during the day. The internal shading (roof and side walls) is undesirable, since it drastically increased the generated thermal radiation in the greenhouse by 147% and strongly increased the greenhouse air temperature during the day. Shading the side-walls is not recommended because it significantly reduces the transmitted solar radiation in the morning and afternoon (when the outside irradiance is low) and is useless at around noon when the outside irradiance is extremely high.

In arid regions, drastic seasonal variations in the climatic parameters are common; thus, a high potential of geothermal effects for heating/cooling applications is expected. However, such applications are very limited in these regions due to the lack of information about underground temperature profiles of the surface and shallow zones. Therefore, this study aims to (i) measure the underground temperature profile for one year to determine the optimum depth for burying EAHE pipes; (ii) examine the possibility of water vapour condensation occurring in the buried EAHE pipes, if the air let into the pipes was humid; and (iii) quantify the maximum cooling/heating capacity, if an EAHE was implemented. The results show that a 3-m depth is optimal to bury EAHE pipes, where the ground temperature is 32 °C in the summer and 29 °C in the winter. These temperatures would provide a maximum cooling/heating capacity of 1000/890 MJ day⁻¹ for each 1 m³ of humid air exhausted from a greenhouse. If the EAHE were to operate in a closed loop with a greenhouse, the condensation of water vapour in the EAHE pipes would be impossible during the cooling process. The results of this study are useful for designers using geothermal effects for indoor space cooling and heating in arid regions.

Instead of fossil fuels, clean renewable energy resources are being used to meet space heating and cooling needs, to reduce global warming and air pollution worldwide. In the desert of the Arabian Peninsula, extensive solar irradiance and drastic variations in air temperatures (daily and/or seasonally) are common; thus, geothermal energy resources are a promising solution that is nearly independent of weather fluctuations. Due to a lack of information about in-ground temperature profiles in these regions, the use of geothermal energy resources for domestic applications is very limited. Therefore, this study aimed to measure the in-ground temperature (T_g) up to 3.5 m in depth for one year. Due to the difficulty of digging in the ground (i.e., gravelly sand; rocky, dry soil), numerical equations were adopted and used to simulate the in-ground temperature (T_g) for a depth > 3 m. These equations were validated by comparing the measured and simulated values of T_g for depths ≤ 3 m under extreme weather conditions. The validation yielded a mean absolute error (E_MA) of ≤ 1.2 °C and a root mean square error (E_RMS) of ≤ 1.42 °C. The measurements showed that at 3 m depth, the in-ground temperature was 32 °C in summer and 29 °C in winter. The simulation showed that values of T_g increased with depth in winter and decreased in summer and became constant as 30 °C at 13 m depth throughout the year (i.e., the undisturbed ground temperature (UGT)). This temperature would provide considerable heating and cooling capacity if an earth-to-air heat exchanger were implemented in arid regions where ambient temperatures exceed 47 °C on summer days and drop below 10 °C on winter nights. The theoretical prediction of T_g using the proposed equations is a useful tool for designers who use geothermal effects for indoor space cooling and heating in the desert of arid regions.

Solar desalination is a promising sustainable solution to overcome the scarcity of fresh water in the deserts of arid regions. The productivity of a solar still depends mainly on its design parameters and the meteorological conditions of its location (longitude and latitude angles). Therefore, this study aimed to optimize the main design parameters of a single-slope solar still for freshwater production in the arid climate of the central region of Saudi Arabia (24°4′ N, 32.89° E). Experiments were conducted on four identical solar stills, with the same basin surface area and air gap distances (d) of 14, 16, 18, and 20 cm, respectively. The stills operated using three basin water depths (h) of 0.5, 1, and 1.5 cm on clear sunny days. The performance and productivity of the four stills were evaluated. The results showed that reducing the air gap distance (d) and water depth (h) significantly enhanced the distillate freshwater yield, and the optimum ratio of the length/width is 2 and of the back/front wall height is 3.65. Specifically, at a low water depth (h) of 0.5 cm, the daily distillate yield of the solar still increased by about 11% when the air gap distance (d) decreased from 20 to 14 cm. For the lowest air gap distance (d) of 14 cm, the distillate yield increased by about 23% when h decreased from 1.5 to 0.5 cm. Using the measured parameters, several numerical correlations have been developed to estimate the desalination rate (m_c) as a function of the solar irradiance (I_s) and ambient temperature (T_am). The developed correlations can be used successfully to estimate the values of m_c instead of the prohibitive experimental measurements. The stills showed excellent performance in the arid climate and reduced water salinity from 31,250 to 495 ppm. This should encourage decision-makers to expand investment in solar desalination to sustainably develop the deserts of arid regions.