Optimization of Nitrogen Requirement of Indian Mustard (Brassica juncea L.) Genotypes under Populus deltoides-Based Agroforestry System

Agroforestry systems incorporating woody perennials such as Populus deltoides offer promising solutions for sustainable land use and enhanced agricultural productivity. This study evaluated the performance of three Indian mustard genotypes (RCH 1, PHR 126, and PBR 357) under four nitrogen (N) levels (0, 100, 125, and 150 kg ha-1) within a poplar-based agroforestry system over two consecutive years (2020-21 and 2021-22) at PAU, Ludhiana. The experiment was laid out in a randomized complete block design. Results showed that increasing nitrogen levels significantly improved growth parameters, number of seeds per siliqua, and productivity. Among the genotypes, PBR 357 recorded the highest plant height, dry matter accumulation, and chlorophyll index. Interaction effects between genotypes and nitrogen levels were significant for seed yield, stover yield, and number of seeds per siliqua. Genotype PBR 357 with application of 150 kg N ha-1 recorded highest seed yield (19.17 and 17.30 q ha-1), and stover yield (68.82 and 61.78 q ha-1). Physiological efficiency and partial factor productivity were highest at 100-125 kg N ha-1, indicating efficient nutrient utilization at moderate N levels. The study highlights PBR 357 as a suitable mustard genotype for integration into poplar-based agroforestry, with 150 kg N ha-1 identified as the optimum dose for maximizing productivity under such systems.