A hydroponic experiment was conducted in a greenhouse during (April-May 2021) at Tishreen University using Nutrient Culture System. The study consisted of different (NO 3-:NH 4 +) ratios (100:0, 75:25, 50:50, 25:75, 0:100). The experiment lasted for 24 days. Tomato plant growth, pH levels, water absorption, and its relation to nutrient acquisition (H 2 PO 4-, K +, NH 4 +, NO 3-) were measured twice a week based on nutrient depletion from the nutrient solution. Growth of tomato plants was similar at 100:0, 75:25, and 50:50 (NO 3-:NH 4 +). A high toxicity effects were recorded at high ammonium concentrations in the nutrient solution, especially in 100% ratios. Results showed that shoot dry weight decreased by 36-75.5% at 75% and 100% NH 4, respectively. The root dry weight decreased by 70.3% at the 100% NH 4 treatment. When nitrate was the sole nitrogen source, there was an increase in the cumulative absorption of water, NO 3-, P, and K, and it decreased with the introduction of NH 4 to the nutrient solution. It seems that nitrate can regulate NH 4 absorption when both are present in the nutrient solution. Different forms of nitrogen influenced pH changes (set to pH=6). The pH increased above 7 in 100:0 and 75:25 (NO 3-:NH 4 +) treatments, while decreased to 4.5 in the 25:75 treatment and to 3 in the 0:100 treatment. This was due to the effect of nitr 1 ogen form (NO 3-:NH 4 +) on the release of OH-\H + in order to cation/anion balance in plant uptakes. Nutrient uptake was better in nitrate treatment, especially in 100% and 75% nitrate addition. Water uptake was closely correlated to nutrient uptake, especially nitrate and potassium, which indicates that water uptake is the main driving force for nutrient absorption, which in turn enhances plant growth. Water consumption increased with the increase of nitrate concentrations, especially in the 100:0 and 75:25 (NO 3-:NH 4 +) treatments. Plants grown in NH 4 showed a significant decrease in water consumption regardless of NH 4 concentration. Different forms of nitrogen influenced pH changes (set to pH=6). The pH increased above 7 in 100:0 and 75:25 (NO 3-:NH 4 +) treatments, while it decreased to 4.5 in the 25:75 treatment and to 3 in the 0:100 treatment. And it seems like tomato plants prefer ammonium over nitrate when they are in equal proportions. This is shown by the low pH detected. This was due to the effect of nitrogen form (NO 3-:NH 4 +) on the cation/anion uptake balance in plants. Keywords: Hydroponics, tomatoes, nitrogen nutrition, water and nutrient absorption, pH changes.
Alajoze, Bushra & Alloush, Ghiath. (2023). Effect of Nitrate and Ammonium Nutrition on tomato growth, Water Nutrients acquisition, and pH changes in the Nutrient Solution. Tishreen University Journal for Research and Scientific Studies. 44.
Read the complete paper at researchgate.net