Optimization of nitrogen and potassium levels in nutrient solution to improve yield, chlorophyll index, and chemical composition of lettuce (Lactuca sativa L.)

Nitrogen (N) is a key element for plants, and its availability is the main determinant of plant growth and crop production. Potassium (K) also affects crop growth, yield, and quality, as it plays a role in numerous physiological and metabolic processes, including photosynthesis, respiration, signal transduction, osmotic regulation, and growth and development. In order to investigate the effects of N and K in nutrient solution on plant yield, chlorophyll index, and chemical compositions of lettuce (Lactuca sativa L. cv. Siahoo), a factorial experiment was conducted with three levels of nitrogen (۱۰۰, ۲۰۰, and ۳۰۰ mg L-۱) from calcium nitrate source and three levels of potassium (۱۰۰, ۲۰۰, and ۳۰۰ mg L-۱) from potassium sulfate source based on a completely randomized design with three replications. The results showed that the effect of different concentrations of N and K in the nutrient solution on plant yield traits, chlorophyll index, nitrate content, sodium, and macro- and microelements except copper was significant. The highest yield and chlorophyll index were observed at a concentration of ۳۰۰ mg L-۱ N and K, while this treatment contained the lowest (۱۳.۱ mg kg-۱DW) sodium accumulation in the leaves. Plants fed with solutions containing ۱۰۰ and ۳۰۰ mg L-۱ of N and K had the lowest nitrate content (۱۱۴۵ mg N kg-۱DW). The content of zinc, manganese, iron, and magnesium elements in lettuce leaves decreased in parallel with the increase in N and K, while the content of calcium increased. Also, potassium content decreased by ۱۵.۵% along with the increase of N concentration in the nutrient solution. In general, the findings of this study provide basic information regarding N and K values ​​for improving hydroponic nutrient management, which determines the correct amount of N and K required by plants, taking into account their impact on the accumulation rate of other elements as well as plant performance.

کلیدواژه ها:

Antagonistic effects ، Nutritional value ، Leafy greens ، Nitrate accumulation ، اثرات آنتاگونیستی ، ارزش غذایی ، سبزیجات برگی ، تجمع نیترات