Impact of Different Nitrogen and Phosphorus Combinations Along with Naphthalene Acetic Acid on Growth and Yield of Late-Sown Wheat (Triticum aestivum L.)

Abstract

Significant efforts have been made over the past decade to enhance wheat productivity. The application of synthetic plant growth regulators, in combination with nitrogen fertilization, has shown promising results in this regard. This study aimed to evaluate the effects of different nitrogen (N) and phosphorus (P₂O₅) levels, along with the exogenous application of naphthalene acetic acid (NAA), on late-sown wheat under the agro-climatic conditions of Dera Ismail Khan, KP, Pakistan. Data were collected on various agronomic traits, including plant height (cm), spike weight (g), spike length (cm), number of tillers, thousand-grain weight (g), grains per spike, biological yield (kg ha⁻¹), grain yield (kg ha⁻¹), straw yield (kg ha⁻¹), productivity score, and harvest index. Significant differences were observed across different fertilizer and NAA treatment levels. Additionally, physiological parameters such as leaf area index (LAI) at 49 and 98 days after emergence, leaf area duration (LAD) at 49 and 98 days, crop growth rate (CGR), and net assimilation rate (NAR) were also significantly influenced by NAA and fertilizer application. The highest grain yield and yield-related parameters were obtained from the fertilizer treatment of 180 kg N and 120 kg P₂O₅ ha⁻¹ combined with the PGR₂ level (50 ml NAA ha⁻¹). Based on this one-year study, applying 50 ml NAA ha⁻¹ alongside an optimal dose of nitrogen and phosphorus resulted in maximum net returns for wheat production under the agro-ecological conditions of Dera Ismail Khan.