Initial Growth and Physiological Response of Rice with Ammonium Sulfate and Chromolaena odorata Under Water Stress

Drought stress is one of the biggest challenges in rice production, requiring effective fertilization strategies to improve plant resilience. This study evaluated the effect of ammonium sulfate ((NH₄)₂SO₄) and Chromolaena odorata (Cho) fertilization on early growth and physiological responses of rice (Oryza sativa L. cv. Inpago 11) under field capacity (100% WFC) and drought stress (50% WFC) conditions. Experiments were conducted using a divided plot design with three fertilizer treatments control, (NH₄)₂SO₄, and (NH₄)₂SO₄ + Cho) and two levels of water availability. Results showed that at 100% WFC, (NH₄)₂SO₄ + Cho fertilization significantly increased maximum growth potential (48.09%), vigour index (29.77%), and growth speed (16.60%.etmal-1 ) compared to the control. Total chlorophyll and carotenoid contents also increased by 50% and 63.8% in the (NH₄)₂SO₄ + Cho treatment compared to the control. At 50% WFC, differences between treatments became insignificant for most parameters, but proline accumulation increased by 62.5% in the (NH₄)₂SO₄ + Cho treatment compared to the control. This study shows that the combination of (NH₄)₂SO₄ + Cho effectively improves early growth and physiological resilience of rice under optimal conditions, but its effectiveness is reduced under drought stress, emphasizing the importance of adaptive fertilization strategies to water availability.