Salt stress is a major problem worldwide because it decreases yields of many important agricultural crops. Silicon is the second-most abundant element in soil and has numerous beneficial effects on plants, particularly in alleviating stress-related impacts. Pepper is an important crop in the Mediterranean region, but pepper varieties differ in their salinity tolerances. The objective of this research was to test the ability of silicon to mitigate effects of salt stress in both salt-sensitive and salt-tolerant cultivars. Salt damage was evaluated by measuring biomass, photosynthetic-related variables, leaf water potential, and membrane damage. We found that the addition of silicon solute to a growth medium was highly effective in improving plant growth by enhancing photosynthesis, stomatal conductance (g S ), leaf water status, and membrane stability, which in turn led to higher biomass production in salt-stressed pepper plants, especially in a salt-sensitive cultivar. From an agronomic viewpoint, application of Si may provide economically relevant productivity improvements for salt-sensitive pepper genotypes grown under moderate salinity conditions and for salt-tolerant genotype grown under higher-salinity conditions.

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Sound stress is an abiotic stress factor wherein the sound wave form affects the growth and development of plants as an alternative mechanical stress. To explore this, 10-week-old tomato (Solanum lycopersicum) plants were used in this experiment. The tomato plants were exposed to three different frequency values consecutively: 600 Hz in the first week, 1240 Hz in the second week and 1600 Hz in the third week. The decibel (dB) value was adjusted to 90 dB in the sound amplifier. At the end of the experiment, lycopene, vitamin C, total sugar, total acid and total phenol levels were analysed and pH and 0 Brix were measured in tomato fruits. As a result, it was determined that as the sound frequency intensity level increased, the concentration of fruit parameters also increased: lycopene, vitamin C, total sugar, total acid and total phenol. The total phenol content, lycopene content and ascorbic acid of the tomato plants that were exposed to sound waves at different frequencies increased at a rate of 70%, 20% and 14%, respectively. According to the results of all measured parameters in tomato fruits, 1600 Hz has been determined the best of sound wave frequency value.

Due to its importance for organic agriculture, one of the most important agricultural production systems, various sources have been proposed to increase soil organic matter content. Vermicompost is one of those sources known as the resistant last form of farmyard manure which is degraded by earthworms. Soil organic matter or humus and their compounds are nutrient sources that increase physical, chemical and biological quality of soil. Humus and humus compounds improve soil physical, chemical and biological quality parameters increasing rhizosphere aeration and water holding capacity, rehabilitating soil structure, providing plant nutrients and constituting natural media for microorganisms with their regulative effects on soil reactions. In this study, the effects of vermicompost on yield and some growth parameters of lettuce were investigated. For this purpose, a random block designed experiment with 5 different applications was conducted in 3 replicates. The applications were control, vermicompost applications of 100 kg, 200 kg and 300 kg per decare and conventional fertilization. According to the results obtained, yield and growth parameters were improved by vermicompost application when compared to control and conventional fertilization. As a result of this study, it was concluded that 300 kg vermicompost/da is a promising application in lettuce production for optimal yield and soil improvement.

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