Effects of different water levels with potassium and magnesium applications on the yield and yield components of tomato grown in high lime soil

In Türkiye, out of 23.4 million hectares of agricultural land, 20% have acidic soils while 80% have calcareous and alkaline soils. Balanced nutritional practices can enhance the yield and quality of vegetables grown in these soils. Calcium deficiency, or excessive levels of potassium and/or magnesium, can impair the uptake of sufficient calcium by plants. This may lead to physiological disorders such as blossom-end rot (BER), particularly under conditions of high air humidity where calcium deficiency in leaves or fruits becomes more pronounced. In calcareous soils, excess calcium can hinder the absorption of potassium and magnesium by plants. Calcium uptake is largely dependent on water uptake, and due to antagonistic interactions among these elements, calcium may not reach adequate levels within plant tissues. Potassium and magnesium are essential macronutrients that not only increase yield and quality in vegetable cultivation, but also enhance the plant's resistance to diseases and pests. The main problem in tomato production is the nutritional imbalance caused by the imbalance between these three main macronutrients in the soil solution. In this context, the effects of different doses of potassium and magnesium and different water levels on tomato were investigated in a study carried out in the research greenhouse of the Department of Soil Science and Plant Nutrition, Faculty of Agriculture, Selçuk University in 2023. In the study, the effects of three different water levels (70%, 100% and 130% of the field capacity moisture level), three different doses of potassium (0, 600 and 1.200 mg K kg-1) and three different doses of magnesium (0, 300 and 600 mg Mg kg-1) on the yield and yield components of industrial tomato grown in high lime soil (38.2%) were investigated with four replications according to the randomized plot experimental design. According to the results obtained, increasing doses of potassium and magnesium at different water levels significantly (p<0.001) increased tomato yield. The highest tomato yield (2.913 g plant-1) was obtained with the combination "130% + K600 + Mg0". The effects of different water levels together with potassium and magnesium doses on the yield and yield components of processing tomato were found to be statistically significant (p<0.001) and fruit weights varied between 31.08 and 60.10 g according to the applications. The number of fruits per plant varied between 33.00 and 66.00, plant stem diameters between 10.85 and 16.61 mm, plant heights between 60.25 and 98.50 cm, fruit diameters between 41.78 and 51.05 mm, fruit pH values between 4.55 and 4.88, fruit hardness between 1.81 and 11.00 kg cm-², Brix values between 4. 15 and 7.07, fruit titratable acidity (%TA) values were found between 0.37 and 0.87, vitamin C values were found between 5.70 and 15.35 mg 100 g-1, and the ratios of blossom end rot varied between 0.00 and 67.29%. In this study, the macro and micronutrient contents of tomato leaves showed statistically significant differences (p<0.001, p<0.01). Moreover, there were also important correlations between leaf nutrients and yield as well as yield components. The results highlight the importance of maintaining a balanced ratio between exchangeable potassium, calcium, and magnesium in the soil solution, such as Ca/K = 12-13, Ca/Mg = 6-7, and Mg/K = 2, for ensuring optimal nutrition of vegetables and other cultivated plants in terms of these macronutrients.