Climate-Smart Nitrogen Management for Maize: Physiological Growth, Assimilate Partitioning, and Yield Optimization under Different Plant Densities and Nitrogen Strategies

Nitrogen (N) management is a cornerstone of sustainable crop production, directly influencing crop growth, yield, grain quality, farm profitability, and environmental outcomes. In warm agro-ecological regions such as Pakistan, where nitrogen losses through volatilization and leaching are high, inefficient fertilizer use not only reduces farmers’ returns but also degrades soil health and contributes to environmental pollution. This book presents a comprehensive scientific evaluation of how optimizing plant density, nitrogen rate, and timing of nitrogen application can significantly enhance maize productivity, nutritional quality, nitrogen use efficiency (NUE), and sustainability.Based on a two-year field study conducted at the Agricultural Research Farm of NWFP Agricultural University, Peshawar, the research examined maize (Zea mays L.) responses to two plant densities (60,000 and 100,000 plants ha⁻¹), three nitrogen rates (60, 120, and 180 kg N ha⁻¹), and six nitrogen split-application strategies applied at sowing and successive irrigations. The experiment employed a factorial randomized complete block design with split-plot arrangement and four replications, ensuring robust and reliable results. Uniform phosphorus and potassium applications were maintained to isolate nitrogen effects.Findings demonstrate that higher nitrogen rates combined with increased plant density and multiple split applications—particularly when a greater proportion of nitrogen was supplied at later growth stages—significantly improved maize physiological performance. Key growth attributes, including leaf area, leaf area index (LAI), crop growth rate (CGR), absolute growth rate (AGR), light interception, and biomass accumulation, were markedly enhanced. Improved crop physiology resulted in more efficient assimilate partitioning toward reproductive organs, leading to substantial gains in grain yield, stover yield, and total biological yield.Grain yield increased from 3,874 to 5,170 kg ha⁻¹ with optimized nitrogen management, while higher plant density increased yield by approximately 13%. Grain protein concentration improved from 8.15% to 9.25%, directly enhancing food and nutritional quality. Nitrogen use efficiency peaked at 45.5 kg grain per kg N when nitrogen was applied in five strategically timed splits, highlighting reduced nitrogen losses and improved environmental performance.Economically, these improvements translated into higher net returns, reduced cost per kilogram of grain produced, and greater profitability for growers. Environmentally, improved NUE lowered the risk of nitrogen losses, supporting soil health and reducing pollution. Overall, the study provides strong evidence that applying 180 kg N ha⁻¹ in multiple, well-timed splits under optimal plant density offers a climate-smart pathway to sustainable maize production.This book delivers valuable insights for researchers, students, extension workers, policymakers, and progressive farmers, contributing directly to SDG 2 (Zero Hunger), SDG 12 (Responsible Production), SDG 13 (Climate Action), and SDG 15 (Life on Land). It serves as a practical and scientific guide for improving food security, farmer income, and environmental sustainability in Pakistan and similar agro-ecological regions worldwide. Read more