The Effect of Fertilizing with Different N and P Sources on the Growth of Swietenia mahagoni (L.) Jacq. Seedlings Under Water Stress

Drought is a worldwide threat that affects many countries by reducing agricultural production and increasing water scarcity. Swietenia mahagoni (L.) Jacq. (mahogany) is a threatened Endangered tree; it has an important value in world markets as its heartwood is highly resistant to rot and insect damage, surpassing all other global mahogany varieties. It has several ecological services (fuel, timber, medicine, shade, and shelter). This study aims to enhance its growth by using various nitrogen (N) and phosphorus (P) fertilizer sources; and by studying their effect on the growth and drought tolerance of mahogany seedlings to obtain their highest growth using the lowest available water resources. During the two growth seasons (2022-2023) and (2023-2024), a field experiment was conducted at Gemmeiza Agricultural Research Station. Three sources of P fertilizers (single and triple superphosphate and phosphoric acid “H3PO4”) and three N fertilizers (urea, ammonium sulfate (NH4)₂SO₄ and ammonium nitrate (NH4NO3) were applied under the influence of three levels of water regime [100, 75, and 50 % field capacity (FC)]. Results showed that drought stress greatly declined shoot length, leaf area, the total fresh and dry weights of the plant, relative water content, total chlorophyll (a, b), and N, P contents in leaves. Still, they sharply increased root length, water use efficiency, proline, and carbohydrate contents in leaves. All different combinations of N and P fertilizer sources significantly improved the above-mentioned parameters compared to the control. The supply of a combination of (NH₄)₂SO₄ and H3PO4 significantly produced the highest growth.