Optimization of nutrient requirement of Indian mustard (Brassica juncea L.) cultivars under poplar (Populus deltoides) based agroforestry system

Abstract

Field experiments were done to determine optimum nutrient requirement of Indian mustard cultivars intercropped under three- and four-year old poplar block plantation at Bathinda and Ludhiana, Punjab respectively. Three cultivars of Indian mustard, namely Giriraj, RLC 3 and PBR 357 were intercropped under poplar with six nutrient levels viz., F₀: control, F₁: Zn₂₅, F₂: N₇₅P_22.5Zn₂₅, F₃: N₁₀₀P₃₀Zn_25, F₄: N₁₂₅P_37.5Zn₂₅ and F₅: N₁₅₀P₄₅Zn₂₅ kg ha^-1. Application of F₅ significantly increased number of siliquae plant^-1 (15.5 and 12.7%), number of seeds silique^-1 (11.2 and 11.6%), seed (21.5 and 22.0%) and oil yield (18.9 and 19.8%) of Indian mustard cultivars than F₃ at Ludhiana and Bathinda, respectively. Cultivar PBR 357 recorded highest seed yield (1293 and 1375 kg ha^-1) and oil yield (513 and 543 kg ha^-1) at Ludhiana and Bathinda, respectively. Cultivar PBR 357 with F₅ application gave highest seed yield (1682 and 1800 kg ha^-1 at Ludhiana and Bathinda, respectively) than other treatment combinations. Among nutrient levels, F₂ (11.6 and 12.0 kg kg^-1) and among cultivars, PBR 357 (10.3 and 10.9 kg kg^-1) recorded highest nutrient use efficiency at Ludhiana and Bathinda, respectively. Highest agronomic efficiency (AE) of 3.7 kg kg^-1 at both sites and physiological efficiency (PE) of 42.6 and 43.2 kg kg^-1 at Ludhiana and Bathinda, respectively was obtained with F₅. Cultivar Giriraj (3.7 kg kg^-1) and PBR 357 (3.9 kg kg^-1) showed highest AE at Ludhiana and Bathinda, respectively. Cultivar PBR 357 (42.1 kg kg^-1) and Giriraj (41.1 kg kg^-1) showed highest PE at Ludhiana and Bathinda, respectively. Highest apparent recovery (AR) of 44.5 and 45.3% at Ludhiana and Bathinda, respectively was obtained with F₃. Cultivar RLC 3 (43.0%) and PBR 357 (44.5%) recorded highest AR at Ludhiana and Bathinda, respectively. Overall reduction in seed yield of Indian mustard was 17.2 and 20.4% under three- and four-year old poplar plantation than sole crop at Bathinda and Ludhiana, respectively.