Doses of N in the Morphological and Physiological Characteristics of African Mahogany Seedling

Purpose: To analyse the growth of African mahogany (Khaya senegalensis) seedlings, regarding their morphology and physiology, in soil fertilized with different doses of N, from the application of ammonium sulphate. Theoretical framework: Based on scientific articles found on search engines and books in the area of ​​soil fertility and plant nutrition. To support the explanation of how the physiological characteristics of seedlings are related to the nutrition they receive from fertilization. Therefore, the application of different doses to the soil can provide different physiological responses, resulting in greater or lesser growth and dry mass production of plants. Method: The experiment was carried out in a completely randomized design with five doses of N and five replications, using ammonium sulphate as the source. The doses tested were: T0 – without fertilization; T1 – 50 mg dm-3; T2 – 100 mg dm-3; T3 – 150 mg dm-3; T4 – 200 mg dm-3. The seedlings were produced and then transplanted to the definitive container, when it received nitrogen fertilization. These seedlings went through an adaptation process and, at the end of 90 days, the morphological characteristics were evaluated: height, diameter, leaf dry mass, stem dry mass, root dry mass and; physiological characteristics: net photosynthetic rate, transpiration rate, stomatal conductance, intercellular CO2 concentration, vapor pressure deficit and transpiration rate. Results and conclusion: Nitrogen fertilization influenced the morphological and physiological characteristics of African mahogany seedlings. The greatest growth and production of dry mass was observed at doses of 100 and 150 mg dm-3 of N. These results were related to the increase in the net photosynthetic rate, stomatal conductance, transpiration and CO2 concentration. Recommending the most economical dose of 100 mg dm-3 of N. Research implications: These results indicate that nitrogen fertilization is essential for the quality growth of African mahogany seedlings, and the dose to be applied is essential for this to happen, since values ​​lower than this dose may not allow the plant to perform at its maximum. growth potential. Meanwhile, higher doses do not guarantee greater growth and will result in unnecessary expenses and, probably, loss of growth due to toxicity. Originality/value: Using nitrogen fertilizers, in the correct dose for the species, increases its growth potential and guarantees the production of quality seedlings within the nursery.