Effect of leaf washing with fresh water in sprinkler irrigation with fish effluent on photosynthesis of potato

In recent years, due to lack of water, using wastewater including fish effluents, for agricultural purposes has increased. Depending on water quality, irrigation method and type of crop might change. The elements present in the fish effluent interact with each other and it is possible to increase or decrease the absorption of an element through the leaves to have a negative effect on the yield and growth indicators. Therefore, the aim of this research is to provide solutions for the use of rainbow trout wastewater in the sprinkler irrigation system to provide irrigation water for potato cultivation and the effect of leaf washing with appropriate quality on yield, tuber dry matter percentage, diameter and height of stem, tuber specific weight, chlorophyll, photosynthesis, transpiration and stomatal conductance.This experiment was conducted in research farm No. 2 of Kurdistan University ,Dehgolan plain in Kurdistan province in the form of a factorial experimental format based on a completely randomized design with three replications in the summer of 2019, 2020 and 2021. The investigated factors include irrigation at two levels, A1 (irrigation with well water) and A2 (irrigation with fish farm effluent), as well as washing the leaves of the plant in four levels, B1 (Before applying fish farm effluent to the leaves, they were washed for ten minutes with fresh water), B2 (after applying fish farm effluent to the leaves, they were washed for ten minutes with fresh water), B3 (The leaves were washed with fresh water for ten minutes both before and after applying the fish farm effluent to them) , B4 (the leaves were not washed at all).Sprinkler irrigation system with micro sprinkler was used to irrigate. At the end of the growing season, the tuber yield values of different treatments were measured. Chlorophyll meter (SPAD-502-Minolta-Japan) was used in order to measure chlorophyll of leaf. The indicators related to gas exchange including photosynthesis, stomatal conductance and transpiration were measured by a portable device (ADC BioScientific LCi Analyzer Serial No. 32648). Data were analyzed with Rstudio, and mean values of the treatments were compared by the least significant difference (LSD) test at 5% and 1% significance level.The results showed that washing the leaves with fresh water significantly affected on the yield and other growth indicators. The highest amount of yield, stem diameter, specific gravity of potato, chlorophyll meter reading, photosynthesis, transpiration and stomatal conductance were 550.8 grams per pot, 9.941 mm, 1.113 g cc-1, 53.59, 22.00 (μmol m-2 s-1), 7.028 (mmol m-2 s-1), 0.4439 (mmol m-2 s-1), respectively. These amounts were results of applying B3 treatment. Also, the highest percentage of potato tuber dry matter was 13.3% and the highest figure for stem height was 35.46 cm, which were the result of applying B4 treatment.The results of this research show that compared to well water, fish effluent increased yield of potato by 16.4%, stem diameter by 4.67%, stem height by 3.72%, chlorophyll meter reading by 9.67%, and stomatal conductance by 15.40%. Also, the results showed that treatment B3 compared to B4, increased yield 64.78%, stem diameter 39.55%, tuber specific weight 48.54%, chlorophyll meter reading 41.21%, photosynthesis by 4.40%, transpiration by 25.86% and stomatal conductance by 10.13%. It is suggested to use the strategy of simultaneous use of fish effluent and fresh water in the sprinkler irrigation system to increase yield and growth indicators.