Impact of Irrigation Timing and Weed Management Practices on Chlorophyll Content and Morphological Traits of Tomato (Solanum lycopersicum Mill.)

Weeds are a major biotic constraint; compete with crop for the same resources and ultimately reduce productivity. This study evaluated the impact of irrigation intervals and weed management treatments on chlorophyll content and morphological growth of tomato to find an appropriate integrated weed management strategy. Two-year field experiments (2018/2019) were conducted at district Mardan (34°15′38″ N and 72°6′36″ E). Tomato F1 hybrid (Taj‑3592) was transplanted during March. The experiments were laid out in a randomized complete-block design in split-plot arrangement with three replications. The main block comprised three irrigation intervals (3, 6, and 9 days) and the sub-block included weed management treatments: transparent polythene, black polythene, weeding except Orobanche, sole weeding of Orobanche, weeding of all weeds, copper oxychloride 1.5 kg a.i ha⁻¹ (single dose), copper oxychloride 1.5 kg a.i ha⁻¹ (split doses), copper oxychloride + humic acid 25 kg ha⁻¹ (single dose), copper oxychloride + humic acid 25 kg ha⁻¹ (split doses), copper sulphate 2 kg ha⁻¹ (single dose), copper sulphate 2 kg ha⁻¹ (split doses), ammonium sulphate 200 kg ha⁻¹ (single dose), ammonium sulphate 200 kg ha⁻¹ (split doses), pendimethalin 33 EC 1.44 kg a.i ha⁻¹, glyphosate 48 SL 1.5 kg a.i ha⁻¹, and weedy check. Lowest relative weed density (RWD) of O. cernua (2.23%) and highest RWD of O. cernua (38.01%) were recorded in the 3‑ and 9‑day irrigation intervals, respectively. However, 3‑day irrigation interval resulted in highest fresh weed biomass (5794 kg ha⁻¹). Moreover, the 6‑day irrigation interval significantly increased chlorophyll content by 11 and 5%, leaf area by 23 and 6%, and number of branches plant⁻¹ by 30 and 22% compared to 9‑ and 3‑day irrigation intervals, respectively. Among the weed management treatments, black polythene resulted in the highest weed control efficiency (96%), increasing chlorophyll content by 16%, leaf area by 33%, and number of branches plant⁻¹ by 64% vs. weedy check. Consequently, 6‑day irrigation intervals × black polythene could be the best weed management strategy, followed by transparent polythene, weeding of all weeds, pendimethalin, glyphosate, and ammonium sulphate.