Evaluating the Effects of Potassium and Naphthalene Acetic Acid on Drought Tolerance of Wheat
Keywords:
Wheat, Potassium, Naphthalene Acetic Acid, Foliar application, Grain yield, Growth Attributes, Rainfed agricultureAbstract
Wheat productivity in semi-arid and rainfed regions is severely affected by drought stress, which limits growth, physiological efficiency, and yield. “A field study was conducted during the Rabi season 2024–2025 at the University Research Farm, Koont (Pothowar region, Punjab, Pakistan) to evaluate the effects of foliar-applied Naphthalene Acetic Acid (NAA) and Potassium Nitrate (KNO₃) on growth, physiological traits, drought tolerance, and yield performance of wheat. The experiment was conducted using a Randomised Complete Block Design (RCBD) with eight treatments and three replications. Treatments comprised: T1 (Control), T2 (NAA 50 ppm), T3 (NAA 100 ppm), T4 (NAA 150 ppm), T5 (KNO₃ 2%), T6 (NAA 150 ppm + KNO₃ 2%), T7 (NAA 100 ppm + KNO₃ 2%), and T8 (NAA 50 ppm + KNO₃ 2%). Foliar applications were applied at the tillering and booting stages. Data were recorded for chlorophyll content, crop growth rate, plant height, spike length, number of grains per spike, 1000-grain weight, and grain yield. The results showed that the combined application of NAA and potassium significantly improved physiological and yield parameters compared to individual applications and control treatment. The highest grain yield was recorded in treatment T6 (NAA 150 ppm + KNO₃ 2%), which produced significantly higher chlorophyll content and crop growth rate. Chlorophyll content ranged from 34.06 (T1) to 41.09 (T6). Values for T2, T3, T4, T5, T7, and T8 were 35.93, 37.02, 38.48, 40.11, 38.22, and 38.98, respectively. Crop growth rate increased from 8.51 g m ² day⁻¹ in control to 13.64 g m⁻2 day-1 in T6, while T2, T3, T4, T5, T7, and T8 recorded 10.05, 10.50, 11.86, 12.87, 11.88, and 12.45 g m⁻2 day-1, respectively. Plant height improved from 85.16 cm (T1) to 102.81 cm (T6). Other treatments produced heights of 89.88 cm (T2), 93.13 cm (T3), 95.82 cm (T4), 98.57 cm (T5), 95.34 cm (T7), and 98.66 cm (T8). Spike length plant-1 increased from 8.33 cm (T1) to 11.02 cm (T6), with intermediate values of 9.07, 9.19, 9.85, 10.56, 10.01, and 10.21 cm under T2, T3, T4, T5, T7, and T8, respectively. Spikelets spike-1 ranged from 13.94 (T1) to 18.68 (T6), while T2, T3, T4, T5, T7, and T8 recorded 15.00, 15.96, 17.01, 18.06, 16.97, and 17.96 spikelets spike-1, respectively. The highest 1000-grain weight (43.40 g), grain yield (4655.85 kg ha⁻¹), biological yield (10327.94 kg ha⁻¹), and harvest index (44.84%) were obtained in T6, whereas control plots recorded 36.83 g, 3216.27 kg ha⁻¹, 8210.08 kg ha⁻¹, and 38.77%, respectively. Grain yield under T2, T3, T4, T5, T7, and T8 was 3459.97, 3701.05, 4195.93, 4506.53, 4351.55, and 4506.53 kg ha⁻¹, respectively. The results were statistically significant at P ≤ 0.05. The improvement in yield may be attributed to enhanced stomatal regulation, osmotic adjustment, and improved nutrient uptake under drought conditions. The improvement in growth and yield parameters under integrated treatment may be attributed to improved photosynthetic efficiency, osmotic adjustment, water use efficiency, and better assimilate partitioning under drought stress conditions. The study concluded that the integrated application of potassium and auxin is an effective strategy for improving wheat productivity under drought stress conditions and can be recommended for semi-arid and rainfed agricultural systems.
Keywords: Wheat, Potassium, Naphthalene Acetic Acid, Foliar application, Grain yield, Growth attributes, Rainfed agriculture, Drought stress, Water Use Efficiency, Crop Growth Rate.
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