Although the application of chemical fertilizers to crops promotes plant growth and yield, their continuous use affects soil heath and creates environmental pollution. On the other hand, plant biostimulants improve nutrients absorption, plant growth, yield and produce quality and are environment-friendly. Therefore, an experiment was conducted during 2021-22 to evaluate the effect of some biostimulants on the performance of the apple cv. Anna, planted in a sandy loam soil at Marsa Matruh governorate, Egypt. Ninety trees were randomly selected and sprayed with 4 or 6% moringa leaf extract (MLE), 0.3 or 0.4% seaweed extract (SWE), 1000 or 2000 mg L⁻¹ Fulvic acid (FA), 4% MLE + 0.3% SWE + 1000 mg L⁻¹ FA (combination 1), or 6% MLE + 0.4% SWE + 2000 mg L⁻¹ FA (combination 2) before flowering, during full bloom and one month later and compared with a control (untreated trees). The results demonstrated that spraying MLE, SWE or FA or their combinations positively improved the vegetative growth, fruit set %, fruit yield and fruit physical and chemical characteristics as well as leaf nutritional status. The positive effect of MLE, SWE and FA was increased in parallel to an increase in the used concentration of each one of them. The highest increments in the measured parameters were accompanied by the application of combination 2 over the other treatments.

To study the effect of potassium nitrate, calcium nitrate and kaolin (Aluminum silicate) on pomegranate cv. Wonderful, this study was conducted during 2020–2021 to investigate the possibility of minimizing the percentages of sunburn and fruit cracking and ameliorating the yield and fruit quality of pomegranate during the aforementioned period. Four sprays consisting of potassium nitrate at 1%, 2% and 3%, calcium nitrate at 2%, 3% and 4%, kaolin at 2%, 4% and 6% and water only (control) were sprayed on pomegranate trees during May, July, and August. The results showed that through spraying the fruit at set percentages, fruit yield was greatly increased through the spraying of potassium nitrate, calcium nitrate and kaolin, particularly the application of potassium nitrate at 3% and 4% and kaolin at 6% as opposed to than the other percentages. In addition, the percentages of fruit cracking and sunburn were markedly lessened by the application of calcium nitrate at 4% and 6% and also by kaolin at 6%. Moreover, the fruit content from TSS, total sugars and anthocyanin, was improved through the spraying of potassium nitrate at 2% and 3%, whereas the fruit weight and firmness were improved by the application of calcium nitrate at 4% and kaolin at 6%.

A two-year (2020-21) study was conducted to investigate the possibility of relying of ten-years old pear trees grown on sandy loam soil irrigated by drip on citric acid (CA), gibberellic acid (GA₃) and humic acid (HA). The CA was applied at the concentrations of 500, 1000 and 1500 ppm, GA₃ at 50, 100 and 150 ppm and HA at 3, 4 and 5%, whereas water spray was used as the control. The results of our study proved that CA, GA₃ and HA improved the shoot length, shoot thickness, leaf area and leaf chlorophyll of pear as compared with the control. Moreover, they also positively increased the fruit set percentage and final yield of ‘Le Conte’ pear. The fruit weight, size and firmness were also improved under the influence of aforementioned treatments. The fruit soluble solids, total sugars, leaf nitrogen, leaf phosphorus and leaf potassium of pear were also enhanced as compared with the control. Additionally, spraying of GA₃ at 150 ppm, as well as, HA at 5 and 4% were the superior treatments and showed the most significant impact on plant growth, yield, fruit quality and leaf mineral content of pear. This study provides a basis for the future elucidation of HA-, GA₃- and CA-modulated molecular mechanisms in pear, which can make a significant contribution in the scientific community.

Weather fluctuations significantly affect the growth and production of orchard crops such as mango, leading to a substantial decrease in tree growth, flowering rate, yield, and fruit quality. One of these weather factors is drought, which negatively influences multiple physiological processes in plants. It increases the transpiration rate and decreases the cell turgidity, stomatal regulation, osmoregulation, water utilization efficiency, and the development of the deep root system; consequently, it decreases the final production and fruit quality. Therefore, the present study was performed in the 2022–2023 seasons to study the role of the spraying of Selenium (Se), Titanium (Ti), and Silicon (Si) nanoparticles on the growth parameters, yielding, fruit physical and chemical characteristics, and leaf mineral composition of mango cv. Keitt. Mango trees were sprayed during the vegetative season 2022–2023 three times, starting in April with three weeks intervals, by 5, 10, and 20 mg/L Se; 40, 60, and 80 mg/L Ti; and 50, 100, and 150 mg/L Si. The results showed that the extern spray of nanoparticles from these micronutrients improved the growth attributes, yielding and fruit quality of mango trees by reducing the effect of undesirable stressful conditions. The results also indicated that the extern implementation of 150 mg/L Si, 60 mg/L Ti and 20 mg/L Se gave the best increments in the shoot number, length, thickness, leaf area, and leaf chlorophyll contrasted to the else sprayed treatments. Besides, they also improved the fruit set percentages, fruit yields, fruit physical and chemical characteristics and nutritional status of mango trees in both tested seasons.

A 2020–2021 study was performed on five-year-old guava trees to examine the influence of the foliar application of three amino acids, glycine, arginine, and glutamic acid, at a concentration of 500 or 1000 ppm. Additionally, two combinations of the three mentioned amino acids were also applied: 500 glycine + 500 arginine + 500 glutamic acid (combination 1) and 1000 glycine + 1000 arginine + 1000 glutamic acid (combination 2), and compared with a control (untreated trees). The results indicated that the application of the three amino acids, solely or in combination, was effective at increasing the shoot length, shoot diameter, and leaf chlorophyll. Additionally, the applied treatments also improved markedly the fruit set percentage, fruit yield, fruit firmness, fruit content of total soluble solids (TSS %), vitamin C (VC), and total sugars as well as the leaf mineral content (nitrogen, potassium, and phosphorus) compared with untreated trees in 2020 and 2021. Moreover, the results indicated that the combinations were more effective than individual applications and that glycine had a greater influence than arginine or glutamic acid, particularly when it was applied at 1000 ppm.

Influence of foliar application of potassium nitrate and copper sulfate on the production and quality of Pear cv. Le Conte was carried out at Horticulture Research Farm and Postharvest Laboratory, The University of Agriculture Peshawar-Pakistan, during the year 2018–19. The aim of the study was to get quality pear production with minimal disease incidence. The research was carried out in a randomized complete block design with three replications. The study contained two factors, i.e., different concentrations of potassium nitrate (0%, 1%, 2%, and 3%) as Factor A, while different levels of copper sulfate (0%, 0.2%, 0.4%, 0.6%, and 0.8%) as factor B and the treatments were applied in spring season at the fruit set stage. The application of 2% potassium nitrate to the pear plants resulted in heaviest fruit (188.30 g), maximum fruit volume (203.80 cm³), fruit yield tree⁻¹ (60.13 kg) with minimum fruit drop (8.52%) and disease incidence (5.28%), while maximum fruit firmness (7.66 kg.cm⁻²), total soluble solids (12.40 ^○Brix), fruit juice pH (5.38), ascorbic acid content (5.56 mg.100 g⁻¹) while minimum Titratable acidity (0.41%) were noted in fruits of plants sprayed with 3% potassium nitrate solution. However, the maximum fruit weight (192.04 g), fruit yield tree⁻¹ (59.06 kg), minimum fruit drop (6.75%), and disease incidences (3.54%) were recorded in pear plants applied with 0.6% foliar copper sulfate solution. However, maximum fruit firmness (7.53 kg.cm⁻²), total soluble solids (12.38 ^○Brix), fruit juice pH (5.31), ascorbic acid content (5.22 mg.100 g⁻¹) with minimum Titratable acidity (0.42%) were noted in the plants sprayed with 0.8% copper sulfate solution. This study will provide a basis for high yield and quality fruit production, which will affect the storability of pear and other important fruit crops. Further studies should be conducted to optimize the dose, timing, and method of application of these fungicides for other pome fruits.