Effect of phosphorus spraying and nutrigation on growth, yield and quality of strawberries in soilless culture

Abstract
Introduction: Strawberries with scientific name (Fragaria × ananassa Duch) are frome Rosaceae family. Today, due to high demand for higher quality and out-of-season strawberries, breeders have turned to greenhouse production and soilless cultivation. Hydroponics is the knowledge of planting plants without the use of soil, in which micro and macro element is added to the water (Tullaie, 2002). Excessive consumption of chemical fertilizers and high prices of fertilizers are some of the reasons for the increase in production costs. Due to the shortage of phosphorus ore mines in Iran and the need to import to provide the required phosphorus fertilizer and sanitary conditions, leaf nutrition is one of the ways to reduce consumption in chemical fertilizers. Phosphorus is one of the most macro element nutrients and is highly mobile in plant organs, especially in flowers and seeds. After nitrogen the phosphorus is the second limiting factor performance (Shen et al., 2011). Phosphorus in biochemical processes, compositions energy and energy transfer mechanisms involved (Tabatabaei, 1392). Phosphorus in strawberries is affects the size, shape of the fruit, ability to retain and form the color of the fruit. It also contributes to increased root formation and better plant growth and development. Phosphorus acts as a substrate and regulator of anti-oxidative stress. Rising prices for chemical fertilizers, the need for economical production and pollution of groundwater due to unconventional use of chemical fertilizers are some of the problems that can be solved with proper planning. Therefore, the purpose of this project is to investigate the effect of consumption method including phosphorus solution and phosphorus spraying from the source (Monopotassium phosphate) on the quality of Strawberry Paros cultivar and determine the appropriate concentration of solution on vegetative and yield properties.
materials and methods: This experiment was performed in November 2017 in the hydroponic research greenhouse of Shahed University. The treatments included three different concentrations of phosphorus foliar application (F) (0, 5, 10 mg/l) and three different concentrations of phosphorus solution (N) (5, 10, 20 mg/l) from the source of Monopotassium phosphate. For the culture, a rectangular cube 45 cm long and 35 cm wide was filled with pumice. In each bag, 3 strawberry seedlings were planted with the appropriate distance. Greenhouse temperature and humidity were regularly adjusted by the central system for proper growth. Different concentrations of phosphorus solution were placed in barrels were in the main source, which were given to the plant in certain amounts during the growing period through irrigation. The other nutrients were the same in all treatments. Phosphorus concentrations sprayed after opening 80% of the flowers at one time. To measure total yield, after ripening strawberry fruits belonging to the plants of each experimental unit were harvested and weighed. Leaf area was measured with leaf area meter. To measure the fresh and dry weight of the leaves, a plant bush was selected where the plant had full growth. The weight of the leaves of each treatment was weighed by digital scale with an accuracy of 0.001 g. For dry weight, the leaves were placed in an oven at 75 C for 48 hours and weighed after complete drying. The volume of the root was taken based on the displaced of water transferred in the graduated cylinder divided by the density of the water. To measure titratable acidity, 0.1% sodium hydroxide was used to change the color of the juice in the presence of a few drops of phenolphthalein reagent. Fruit diluted with distilled water with 1% starch reagent was measured by 10 milliliters of potassium iodide 5% and titration by copper sulfate 1% to the stage of color to brown change to measure vitamin C. The pH differential method was used to measure the total amount of anthocyanin (Wang and Gao, 2013). This experiment was performed as a factorial in a completely randomized design in three replications. Data analysis was performed by SAS software and mean comparison using Duncan's.